RESUMEN
AT-hook motif nuclear localization (AHL) proteins play essential roles in various plant biological processes. Yet, a comprehensive understanding of AHL transcription factors in walnut (Juglans regia L.) is missing. In this study, 37 AHL gene family members were first identified in the walnut genome. Based on the evolutionary analysis, JrAHL genes were grouped into two clades, and their expansion may occur due to segmental duplication. The stress-responsive nature and driving of developmental activities of JrAHL genes were revealed by cis-acting elements and transcriptomic data, respectively. Tissue-specific expression analysis showed that JrAHLs had a profound transcription in flower and shoot tip, JrAHL2 in particular. Subcellular localization showed that JrAHL2 is anchored to the nucleus. Overexpression of JrAHL2 in Arabidopsis adversely affected hypocotyl elongation and delayed flowering. Our study, for the first time, presented a detailed analysis of JrAHL genes in walnut and provided theoretical knowledge for future genetic breeding programs.
Asunto(s)
Arabidopsis , Juglans , Juglans/genética , Juglans/metabolismo , Hipocótilo/genética , Hipocótilo/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Secuencias AT-Hook/genética , Fitomejoramiento , Flores/genética , Flores/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Regulación de la Expresión Génica de las PlantasRESUMEN
AHL (AT-HOOK MOTIF NUCLEAR LOCALIZED) protein is an important transcription factor in plants that regulates a wide range of biological process. It is considered to have evolved from an independent PPC domain in prokaryotes to a complete protein in modern plants. AT-hook motif and PPC conserved domains are the main functional domains of AHL. Since the discovery of AHL, their evolution and function have been continuously studied. The AHL gene family has been identified in multiple species and the functions of several members of the gene family have been studied. Here, we summarize the evolution and structural characteristics of AHL genes, and emphasize their biological functions. This review will provide a basis for further functional study and crop breeding.
Asunto(s)
Secuencias AT-Hook , Proteínas de Arabidopsis , Secuencias AT-Hook/genética , Proteínas de Arabidopsis/genética , Núcleo Celular/genética , Núcleo Celular/metabolismo , Fitomejoramiento , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismoRESUMEN
The AT-hook motif containing nuclear localized (AHL) gene family, controlling various developmental processes, is conserved in land plants. They comprise Plant and Prokaryote Conserved (PPC) domain and one or two AT-hook motifs. DcAHLc1 has been proposed as a candidate gene governing the formation of the carrot storage root. We identified and in-silico characterized carrot AHL proteins, performed phylogenetic analyses, investigated their expression profiles and constructed gene coexpression networks. We found 47 AHL genes in carrot and grouped them into two clades, A and B, comprising 29 and 18 genes, respectively. Within Clade-A, we distinguished three subclades, one of them grouping noncanonical AHLs differing in their structure (two PPC domains) and/or cellular localization (not nucleus). Coexpression network analysis attributed AHLs expressed in carrot roots into four of the 72 clusters, some of them showing a large number of interactions. Determination of expression profiles of AHL genes in various tissues and samples provided basis to hypothesize on their possible roles in the development of the carrot storage root. We identified a group of rapidly evolving noncanonical AHLs, possibly differing functionally from typical AHLs, as suggested by their expression profiles and their predicted cellular localization. We pointed at several AHLs likely involved in the development of the carrot storage root.
Asunto(s)
Secuencias AT-Hook/genética , Daucus carota/crecimiento & desarrollo , Daucus carota/genética , Desarrollo de la Planta/genética , Proteínas de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/genética , Regulación de la Expresión Génica de las Plantas/genética , Filogenia , Transcriptoma/genéticaRESUMEN
In many eukaryotic systems during immune responses, mitogen-activated protein kinases (MAPKs) link cytoplasmic signaling to chromatin events by targeting transcription factors, chromatin remodeling complexes, and the RNA polymerase machinery. So far, knowledge on these events is scarce in plants and no attempts have been made to focus on phosphorylation events of chromatin-associated proteins. Here we carried out chromatin phosphoproteomics upon elicitor-induced activation of Arabidopsis The events in WT were compared with those in mpk3, mpk4, and mpk6 mutant plants to decipher specific MAPK targets. Our study highlights distinct signaling networks involving MPK3, MPK4, and MPK6 in chromatin organization and modification, as well as in RNA transcription and processing. Among the chromatin targets, we characterized the AT-hook motif containing nuclear localized (AHL) DNA-binding protein AHL13 as a substrate of immune MAPKs. AHL13 knockout mutant plants are compromised in pathogen-associated molecular pattern (PAMP)-induced reactive oxygen species production, expression of defense genes, and PAMP-triggered immunity. Transcriptome analysis revealed that AHL13 regulates key factors of jasmonic acid biosynthesis and signaling and affects immunity toward Pseudomonas syringae and Botrytis cinerea pathogens. Mutational analysis of the phosphorylation sites of AHL13 demonstrated that phosphorylation regulates AHL13 protein stability and thereby its immune functions.
Asunto(s)
Proteínas de Arabidopsis/genética , Cromatina/genética , Fosfoproteínas/genética , Inmunidad de la Planta/genética , Secuencias AT-Hook/genética , Secuencias AT-Hook/inmunología , Arabidopsis/genética , Arabidopsis/inmunología , Regulación de la Expresión Génica de las Plantas , Proteínas Quinasas Activadas por Mitógenos/genética , Moléculas de Patrón Molecular Asociado a Patógenos/inmunología , Moléculas de Patrón Molecular Asociado a Patógenos/metabolismo , Fosfoproteínas/inmunología , Fosforilación/genéticaRESUMEN
The timely programmed cell death (PCD) of the tapetum, the innermost somatic anther cell layer in flowering plants, is critical for pollen development, including the deposition and patterning of the pollen wall. Although several genes involved in tapetal PCD and pollen wall development have been characterized, the underlying regulatory mechanism remains elusive. Here we report that PERSISTENT TAPETAL CELL2 (PTC2), which encodes an AT-hook nuclear localized protein in rice (Oryza sativa), is required for normal tapetal PCD and pollen wall development. The mutant ptc2 showed persistent tapetal cells and abnormal pollen wall patterning including absent nexine, collapsed bacula, and disordered tectum. The defective tapetal PCD phenotype of ptc2 was similar to that of a PCD delayed mutant, ptc1, in rice, while the abnormal pollen wall patterning resembled that of a pollen wall defective mutant, Transposable Element Silencing Via AT-Hook, in Arabidopsis (Arabidopsis thaliana). Levels of anther cutin monomers in ptc2 anthers were significantly reduced, as was expression of a series of lipid biosynthetic genes. PTC2 transcript and protein were shown to be present in the anther after meiosis, consistent with the observed phenotype. Based on these data, we propose a model explaining how PTC2 affects anther and pollen development. The characterization of PTC2 in tapetal PCD and pollen wall patterning expands our understanding of the regulatory network of male reproductive development in rice and will aid future breeding approaches.
Asunto(s)
Apoptosis/genética , Flores/crecimiento & desarrollo , Oryza/crecimiento & desarrollo , Oryza/genética , Infertilidad Vegetal/genética , Proteínas de Plantas/metabolismo , Polen/crecimiento & desarrollo , Secuencias AT-Hook/genética , Arabidopsis/genética , Núcleo Celular/metabolismo , Fragmentación del ADN , Flores/genética , Flores/metabolismo , Flores/ultraestructura , Perfilación de la Expresión Génica , Regulación del Desarrollo de la Expresión Génica/genética , Regulación de la Expresión Génica de las Plantas/genética , Redes Reguladoras de Genes , Genotipo , Metabolismo de los Lípidos/genética , Lípidos/análisis , Microscopía Electrónica de Rastreo , Mutación , Oryza/metabolismo , Fenotipo , Proteínas de Plantas/genética , Polen/genética , Polen/metabolismo , Polen/ultraestructura , RNA-Seq , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
A novel gene, OsAHL1, containing an AT-hook motif and a PPC domain was identified through genome-wide profiling and analysis of mRNAs by comparing the microarray of drought-challenged versus normally watered rice. The results indicated OsAHL1 has both drought avoidance and drought tolerance that could greatly improve drought resistance of the rice plant. Overexpression of OsAHL1 enhanced multiple stress tolerances in rice plants during both seedling and panicle development stages. Functional studies revealed that OsAHL1 regulates root development under drought condition to enhance drought avoidance, participates in oxidative stress response and also regulates the content of chlorophyll in rice leaves. OsAHL1 specifically binds to the A/T rich sequence region of promoters or introns, and hence directly regulates the expression of many stress related downstream genes.
Asunto(s)
Secuencias AT-Hook/genética , Oryza/genética , Hojas de la Planta/genética , Estrés Fisiológico/genética , Clorofila/genética , Clorofila/metabolismo , Proteínas de Unión al ADN/genética , Sequías , Regulación de la Expresión Génica de las Plantas , Oryza/crecimiento & desarrollo , Oryza/metabolismo , Estrés Oxidativo/genética , Hojas de la Planta/crecimiento & desarrollo , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Dominios Proteicos/genéticaRESUMEN
MeCP2 is a chromatin-associated protein that is mutated in Rett syndrome. Its methyl-CpG-binding domain interacts with DNA containing methylated cytosine, but other modes of recruitment to the genome have also been proposed. Here, we use in vitro and in vivo assays to investigate the DNA binding specificity of two AT-hook motifs in MeCP2. One exhibits robust sequence-specific DNA binding, whereas the other is a much weaker AT-hook. Our data indicate that these motifs are secondary contributors to DNA binding by MeCP2, and this view is supported by the absence of disease-causing missense mutations at these sites.
Asunto(s)
Secuencias AT-Hook/genética , Metilación de ADN/genética , Proteína 2 de Unión a Metil-CpG/genética , Síndrome de Rett/genética , Secuencia de Bases/genética , Cromatina/genética , Citosina/metabolismo , Proteínas de Unión al ADN/genética , Humanos , Mutación Missense/genética , Síndrome de Rett/patologíaRESUMEN
Proper chromosome alignment and segregation during mitosis depend on cohesion between sister chromatids. Cohesion is thought to occur through the entrapment of DNA within the tripartite ring (Smc1, Smc3 and Rad21) with enforcement from a fourth subunit (SA1/SA2). Surprisingly, cohesin rings do not play a major role in sister telomere cohesion. Instead, this role is replaced by SA1 and telomere binding proteins (TRF1 and TIN2). Neither the DNA binding property of SA1 nor this unique telomere cohesion mechanism is understood. Here, using single-molecule fluorescence imaging, we discover that SA1 displays two-state binding on DNA: searching by one-dimensional (1D) free diffusion versus recognition through subdiffusive sliding at telomeric regions. The AT-hook motif in SA1 plays dual roles in modulating non-specific DNA binding and subdiffusive dynamics over telomeric regions. TRF1 tethers SA1 within telomeric regions that SA1 transiently interacts with. SA1 and TRF1 together form longer DNA-DNA pairing tracts than with TRF1 alone, as revealed by atomic force microscopy imaging. These results suggest that at telomeres cohesion relies on the molecular interplay between TRF1 and SA1 to promote DNA-DNA pairing, while along chromosomal arms the core cohesin assembly might also depend on SA1 1D diffusion on DNA and sequence-specific DNA binding.
Asunto(s)
Segregación Cromosómica/genética , Proteínas Nucleares/genética , Proteínas de Unión a Telómeros/genética , Telómero/genética , Proteína 1 de Unión a Repeticiones Teloméricas/genética , Secuencias AT-Hook/genética , Cromátides/genética , Cromátides/ultraestructura , Proteínas de Unión al ADN/genética , Humanos , Microscopía de Fuerza Atómica , Mitosis/genética , Proteínas Nucleares/metabolismo , Telómero/ultraestructura , Proteínas de Unión a Telómeros/metabolismo , Proteína 1 de Unión a Repeticiones Teloméricas/metabolismoRESUMEN
BACKGROUND: Members of the ancient land-plant-specific transcription factor AT-Hook Motif Nuclear Localized (AHL) gene family regulate various biological processes. However, the relationships among the AHL genes, as well as their evolutionary history, still remain unexplored. RESULTS: We analyzed over 500 AHL genes from 19 land plant species, ranging from the early diverging Physcomitrella patens and Selaginella to a variety of monocot and dicot flowering plants. We classified the AHL proteins into three types (Type-I/-II/-III) based on the number and composition of their functional domains, the AT-hook motif(s) and PPC domain. We further inferred their phylogenies via Bayesian inference analysis and predicted gene gain/loss events throughout their diversification. Our analyses suggested that the AHL gene family emerged in embryophytes and further evolved into two distinct clades, with Type-I AHLs forming one clade (Clade-A), and the other two types together diversifying in another (Clade-B). The two AHL clades likely diverged before the separation of Physcomitrella patens from the vascular plant lineage. In angiosperms, Clade-A AHLs expanded into 5 subfamilies; while, the ones in Clade-B expanded into 4 subfamilies. Examination of their expression patterns suggests that the AHLs within each clade share similar expression patterns with each other; however, AHLs in one monophyletic clade exhibit distinct expression patterns from the ones in the other clade. Over-expression of a Glycine max AHL PPC domain in Arabidopsis thaliana recapitulates the phenotype observed when over-expressing its Arabidopsis thaliana counterpart. This result suggests that the AHL genes from different land plant species may share conserved functions in regulating plant growth and development. Our study further suggests that such functional conservation may be due to conserved physical interactions among the PPC domains of AHL proteins. CONCLUSIONS: Our analyses reveal a possible evolutionary scenario for the AHL gene family in land plants, which will facilitate the design of new studies probing their biological functions. Manipulating the AHL genes has been suggested to have tremendous effects in agriculture through increased seedling establishment, enhanced plant biomass and improved plant immunity. The information gleaned from this study, in turn, has the potential to be utilized to further improve crop production.
Asunto(s)
Secuencias AT-Hook/genética , Embryophyta/genética , Secuencia de Aminoácidos , Secuencia de Bases , Evolución Biológica , Biomasa , Bryopsida/genética , Bryopsida/crecimiento & desarrollo , Embryophyta/crecimiento & desarrollo , Duplicación de Gen , Expresión Génica , Magnoliopsida/genética , Magnoliopsida/crecimiento & desarrollo , Modelos Moleculares , Datos de Secuencia Molecular , Familia de Multigenes , Fenotipo , Filogenia , Proteínas de Plantas/genética , Plantones/genética , Plantones/crecimiento & desarrollo , Selaginellaceae/genética , Selaginellaceae/crecimiento & desarrollo , Análisis de Secuencia de ADNRESUMEN
Major histocompatibility complexes class II are responsible for the antigen presentation that shapes the repertoire of the adaptive immune responses. All members of the MHCII family of genes are controlled by the same set of conserved transcription factors and promoter elements, resulting in coordinated transcription. We report the role of a previously unidentified AT-hook motif of the MHCII regulatory factor RFX5, and show that this is involved in regulating the transcription of the HLA-DQ, but not HLA-DR, MHCII isotype. Furthermore, PRMT6, an arginine methyltransferase known to methylate AT-hook motifs, downregulates the expression of HLA-DQ, but not HLA-DR, in an AT-hook-dependent manner. This can provide a fine-tuning mechanism for isotype-specific transcriptional regulation, where a post-translational modification modulates the relative levels of the MHCII isotypes.
Asunto(s)
Secuencias AT-Hook/genética , Proteínas de Unión al ADN/genética , Regulación de la Expresión Génica , Antígenos de Histocompatibilidad Clase II/genética , Proteínas Nucleares/genética , Proteína-Arginina N-Metiltransferasas/genética , Secuencia de Aminoácidos , Western Blotting , Línea Celular Tumoral , Proteínas de Unión al ADN/metabolismo , Perfilación de la Expresión Génica , Antígenos HLA-DQ/genética , Antígenos HLA-DQ/metabolismo , Antígenos HLA-DR/genética , Antígenos HLA-DR/metabolismo , Antígenos de Histocompatibilidad Clase II/metabolismo , Humanos , Datos de Secuencia Molecular , Mutación , Proteínas Nucleares/metabolismo , Regiones Promotoras Genéticas/genética , Unión Proteica , Proteína-Arginina N-Metiltransferasas/metabolismo , Factores de Transcripción del Factor Regulador X , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de AminoácidoRESUMEN
Coordination of the onset of flowering with developmental status and seasonal cues is critical for reproductive success in plants. Molecular genetic studies on Arabidopsis mutants that have alterations in flowering time have identified a wide array of genes that belong to distinct genetic flowering pathways. The flowering time genes are regulated through versatile molecular and biochemical mechanisms, such as controlled RNA metabolism and chromatin modifications. Recent studies have shown that a group of AT-hook DNA-binding motif-containing proteins plays a role in plant developmental processes and stress responses. Here, we demonstrate that the AT-hook protein AHL22 (AT-hook motif nuclear localized 22) regulates flowering time by modifying FLOWERING LOCUS T (FT) chromatin in Arabidopsis. AHL22 binds to a stretch of the AT-rich sequence in the FT locus. It interacts with a subset of histone deacetylases. An Arabidopsis mutant overexpressing the AHL22 gene (OE-AHL22) exhibited delayed flowering, and FT transcription was significantly reduced in the mutant. Consistent with the delayed flowering and FT suppression in the OE-AHL22 mutant, histone 3 (H3) acetylation was reduced and H3 lysine 9 dimethylation was elevated in the FT chromatin. We propose that AHL22 acts as a chromatin remodeling factor that modifies the architecture of FT chromatin by modulating both H3 acetylation and methylation.
Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Proteínas de Unión al ADN/genética , Flores/genética , Secuencia Rica en At/genética , Secuencias AT-Hook/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Cromatina/genética , Cromatina/metabolismo , Inmunoprecipitación de Cromatina , Proteínas de Unión al ADN/metabolismo , Flores/crecimiento & desarrollo , Flores/ultraestructura , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Pleiotropía Genética , Immunoblotting , Proteínas Luminiscentes/genética , Proteínas Luminiscentes/metabolismo , Microscopía Electrónica de Rastreo , Microscopía Fluorescente , Microscopía de Interferencia , Mutación , Plantas Modificadas Genéticamente , Unión Proteica , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
The AT-hook motif is a small DNA-binding protein motif that has been found in the high mobility group of non-histone chromosomal proteins. The Arabidopsis genome contains 29 genes encoding the AT-hook motif DNA-binding protein (AHL). Recent studies of Arabidopsis genes (AtAHLs) have revealed that they might play diverse functional roles during plant growth and development. In this report, we mined 20 AHL genes (OsAHLs) from the rice genome database using AtAHL genes as queries and characterized their molecular features. A phylogenetic tree revealed that OsAHL proteins can be classified into 2 evolutionary clades. Tissue expression pattern analysis revealed that all of the OsAHL genes might be functionally expressed genes with 3 distinct expression patterns. Nuclear localization analysis using transgenic Arabidopsis showed that several OsAHL proteins are exclusively localized in the nucleus, indicating that they may act as architectural transcription factors to regulate expression of their target genes during plant growth and development.
Asunto(s)
Secuencias AT-Hook/genética , Genes de Plantas , Oryza/genética , Proteínas de Plantas/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Bases de Datos Genéticas , Regulación de la Expresión Génica de las Plantas , Genoma de Planta , Oryza/metabolismo , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/clasificación , Proteínas de Plantas/metabolismo , Plantas Modificadas GenéticamenteRESUMEN
Grasses have highly specialized flowers and their outer floral organ identity remains unclear. In this study, we identified and characterized rice mutants that specifically disrupted the development of palea, one of the outer whorl floral organs. The depressed palea1 (dp1) mutants show a primary defect in the main structure of palea, implying that palea is a fusion between the main structure and marginal tissues on both sides. The sterile lemma at the palea side is occasionally elongated in dp1 mutants. In addition, we found a floral organ number increase in dp1 mutants at low penetration. Both the sterile lemma elongation and the floral organ number increase phenotype are enhanced by the mutation of an independent gene SMALL DEGENERATIVE PALEA1 (SDP1), whose single mutation causes reduced palea size. E function and presumable A function floral homeotic genes were found suppressed in the dp1-2 mutant. We identified the DP1 gene by map-based cloning and found it encodes a nuclear-localized AT-hook DNA binding protein, suggesting a grass-specific role of chromatin architecture modification in flower development. The DP1 enhancer SDP1 was also positional cloned, and was found identical to the recently reported RETARDED PALEA1 (REP1) gene encoding a TCP family transcription factor. We further found that SDP1/REP1 is downstreamly regulated by DP1.
Asunto(s)
Proteínas de Unión al ADN/genética , Flores/genética , Oryza/genética , Proteínas de Plantas/genética , Secuencias AT-Hook/genética , Secuencia de Aminoácidos , Núcleo Celular/metabolismo , Clonación Molecular , Proteínas de Unión al ADN/clasificación , Proteínas de Unión al ADN/metabolismo , Flores/metabolismo , Flores/ultraestructura , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Hibridación in Situ , Proteínas de Dominio MADS/genética , Microscopía Electrónica de Rastreo , Microscopía Fluorescente , Datos de Secuencia Molecular , Mutación , Oryza/crecimiento & desarrollo , Oryza/metabolismo , Filogenia , Infertilidad Vegetal/genética , Proteínas de Plantas/clasificación , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de AminoácidoRESUMEN
The AKNA gene is part of the 9q32 susceptibility locus for cervical cancer. A single-nucleotide polymorphism at codon 1119 of AKNA, yields a biologically relevant amino acid change (R1119Q) at the DNA binding AT-hook motif. Genotype frequencies in 97 allele pairs were: R/R = 0.597, R/Q = 0.278, Q/Q = 0.123. Q/Q homozygosity was present in 8.33% of healthy controls, 16.67% of patients with cervical intraepithelial neoplasia and 75% of cervical cancer patients. These differences are highly significant for the presence of Q/Q in cervical cancer (p = 0.01, odds ratio 3.66, 95% confidence interval 1.35-9.94). Therefore, AKNA appears to be an important genetic factor associated with the risk cervical cancer.
Asunto(s)
Proteínas de Unión al ADN/genética , Proteínas Nucleares/genética , Polimorfismo de Nucleótido Simple , Factores de Transcripción/genética , Neoplasias del Cuello Uterino/genética , Secuencias AT-Hook/genética , Adulto , Alelos , Femenino , Frecuencia de los Genes , Predisposición Genética a la Enfermedad/genética , Genotipo , Humanos , Persona de Mediana Edad , Oportunidad Relativa , Factores de Riesgo , Neoplasias del Cuello Uterino/patología , Adulto JovenRESUMEN
The Arabidopsis genome encodes 29 AHL (AT-hook motif nuclear localized) proteins, but the function for most of them remains unknown. We report here a study of the AHL22 gene, which was originally identified as a gain-of-function allele that enhanced the phenotype of the cry1 cry2 mutant. AHL22 is a nuclear protein with the binding activity for an AT-rich DNA sequence. AHL22 overexpression delayed flowering and caused a constitutive photomorphogenic phenotype. The loss-of-function AHL22 mutant showed no clear phenotype on flowering, but slightly longer hypocotyls. However, silencing four AHL genes (AHL22, AHL18, AHL27, and AHL29) resulted in early flowering and enhanced ahl22-1 mutant phenotype on the growth of hypocotyls, suggesting genetic redundancy of AHL22 with other AHL genes on these plant developmental events. Further analysis showed that AHL22 controlled flowering and hypocotyl elongation might result from primarily the regulation of FT and PIF4 expression, respectively.
Asunto(s)
Secuencias AT-Hook/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/genética , Flores/genética , Regulación de la Expresión Génica de las Plantas , Hipocótilo/crecimiento & desarrollo , Proteínas de Arabidopsis/genética , Flores/crecimiento & desarrollo , Regulación del Desarrollo de la Expresión Génica , Hipocótilo/genética , Mutación , FotoperiodoRESUMEN
Activation of steroid receptors results in global changes of gene expression patterns. Recent studies showed that steroid receptors control only a portion of their target genes directly, by promoter binding. The majority of the changes are indirect, through chromatin rearrangements. The mediators that relay the hormonal signals to large-scale chromatin changes are, however, unknown. We report here that APRIN, a novel hormone-induced nuclear phosphoprotein has the characteristics of a chromatin regulator and may link endocrine pathways to chromatin. We showed earlier that APRIN is involved in the hormonal regulation of proliferative arrest in cancer cells. To investigate its function we cloned and characterized APRIN orthologs and performed homology and expression studies. APRIN is a paralog of the cohesin-associated Pds5 gene lineage and arose by gene-duplication in early vertebrates. The conservation and domain differences we found suggest, however, that APRIN acquired novel chromatin-related functions (e.g. the HMG-like domains in APRIN, the hallmarks of chromatin regulators, are absent in the Pds5 family). Our results suggest that in interphase nuclei APRIN localizes in the euchromatin/heterochromatin interface and we also identified its DNA-binding and nuclear import signal domains. The results indicate that APRIN, in addition to its Pds5 similarity, has the features and localization of a hormone-induced chromatin regulator.
Asunto(s)
Diferenciación Celular/genética , Ensamble y Desensamble de Cromatina/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/fisiología , Factores de Transcripción/genética , Factores de Transcripción/fisiología , Secuencias AT-Hook/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/fisiología , Diferenciación Celular/efectos de los fármacos , Núcleo Celular/metabolismo , Clonación Molecular , Secuencia Conservada , Proteínas de Unión al ADN/metabolismo , Dominios HMG-Box/genética , Hormonas/farmacología , Humanos , Ratones , Datos de Secuencia Molecular , Señales de Localización Nuclear/genética , Señales de Localización Nuclear/metabolismo , Estructura Terciaria de Proteína/genética , Ratas , Homología de Secuencia de Aminoácido , Factores de Transcripción/metabolismo , Células Tumorales CultivadasRESUMEN
Leaf senescence is the final stage of leaf development and is finely regulated via a complex genetic regulatory network incorporating both developmental and environmental factors. In an effort to identify negative regulators of leaf senescence, we screened activation-tagged Arabidopsis lines for mutants that exhibit a delayed leaf senescence phenotype. One of the mutants (ore7-1D) showed a highly significant delay of leaf senescence in the heterozygous state, leading to at least a twofold increase in leaf longevity. The activated gene (ORE7/ESC) encoded a protein with an AT-hook DNA-binding motif; such proteins are known to co-regulate transcription of genes through modification of chromatin architecture. We showed that ORE7/ESC, in addition to binding to a plant AT-rich DNA fragment, could also modify the chromatin architecture, as illustrated by an altered distribution of a histone-GFP fusion protein in the nucleus of the mutant. Globally altered gene expression, shown by microarray analysis, also indicated that activation of ORE7/ESC results in a younger condition in the mutant leaves. We propose that ectopically expressed ORE7/ESC is negatively regulating leaf senescence and suggest that the resulting chromatin alteration may have a role in controlling leaf longevity. Interestingly, activation of ORE7/ESC also led to a highly extended post-harvest storage life.
Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Cromatina/metabolismo , Hojas de la Planta/genética , Secuencias AT-Hook/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Ensayo de Cambio de Movilidad Electroforética , Regulación de la Expresión Génica de las Plantas , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Histonas/genética , Histonas/metabolismo , Mutación , Análisis de Secuencia por Matrices de Oligonucleótidos , Hojas de la Planta/metabolismo , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
In plants, the chromatin-associated high mobility group (HMG) proteins occur in two subfamilies termed HMGA and HMGB. The HMGA proteins are characterized by the presence of four AT-hook DNA binding motifs, and the HMGB proteins contain an HMG box DNA binding domain. As architectural factors, the HMG proteins appear to be involved in the regulation of transcription and other DNA-dependent processes. We have examined the subcellular localization of Arabidopsis thaliana HMGA, HMGB1, and HMGB5, revealing that they localize to the cell nucleus. They display a speckled distribution pattern throughout the chromatin of interphase nuclei, whereas none of the proteins associate with condensed mitotic chromosomes. HMGA is targeted to the nucleus by a monopartite nuclear localization signal, while efficient nuclear accumulation of HMGB1/5 requires large portions of the basic N-terminal part of the proteins. The acidic C-terminal domain interferes with nucleolar targeting of HMGB1. Fluorescence recovery after photobleaching experiments revealed that HMGA and HMGB proteins are extremely dynamic in the nucleus, indicating that they bind chromatin only transiently before moving on to the next site, thereby continuously scanning the genome for targets. By contrast, the majority of histone H2B is basically immobile within the nucleus, while linker histone H1.2 is relatively mobile.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Núcleo Celular/metabolismo , Cromatina/metabolismo , Proteínas HMGA/metabolismo , Proteínas HMGB/metabolismo , Proteína HMGB1/metabolismo , Transducción de Señal , Secuencias AT-Hook/genética , Secuencia de Aminoácidos , Aminoácidos Básicos/metabolismo , Arabidopsis/citología , Proteínas de Arabidopsis/química , Cromosomas de las Plantas/metabolismo , ADN de Plantas/metabolismo , Recuperación de Fluorescencia tras Fotoblanqueo , Proteínas Fluorescentes Verdes/metabolismo , Proteínas HMGA/química , Proteínas HMGB/química , Proteína HMGB1/química , Histonas/metabolismo , Interfase , Mitosis , Datos de Secuencia Molecular , Señales de Localización Nuclear/metabolismo , Transporte de Proteínas , Protoplastos/citología , Proteínas Recombinantes de Fusión/metabolismo , Plantones/citología , Nicotiana/citologíaRESUMEN
TATA-binding protein-associated factor 1 (TAF1) is an essential component of the general transcription factor IID (TFIID), which nucleates assembly of the preinitiation complex for transcription by RNA polymerase II. TATA-binding protein and TAF1.TAF2 heterodimers are the only components of TFIID shown to bind specific DNA sequences (the TATA box and initiator, respectively), raising the question of how TFIID localizes to gene promoters that lack binding sites for these proteins. Here we demonstrate that Drosophila TAF1 protein isoforms TAF1-2 and TAF1-4 directly bind DNA independently of TAF2. DNA binding by TAF1 isoforms is mediated by cooperative interactions of two identical AT-hook motifs, one of which is encoded by an alternatively spliced exon. Electrophoretic mobility shift assays revealed that TAF1-2 bound the minor groove of adenine-thymine-rich DNA with a preference for the sequence AAT. Alanine-scanning mutagenesis of the alternatively spliced AT-hook indicated that Lys and Arg residues made essential DNA contacts, whereas Gly and Pro residues within the Arg-Gly-Arg-Pro core sequence were less important for DNA binding, suggesting that AT-hooks are more divergent than previously predicted. TAF1-2 bound with variable affinity to the transcription start site of several Drosophila genes, and binding to the hsp70 promoter was reduced by mutation of a single base pair at the transcription start site. Collectively, these data indicate that AT-hooks serve to anchor TAF1 isoforms to the minor groove of adenine-thymine-rich Drosophila gene promoters and suggest a model in which regulated expression of TAF1 isoforms by alternative splicing contributes to gene-specific transcription.
Asunto(s)
Secuencias AT-Hook/genética , Proteínas de Unión al ADN/metabolismo , ADN/metabolismo , Proteínas de Drosophila/metabolismo , Histona Acetiltransferasas/metabolismo , Factor de Transcripción TFIID/metabolismo , Empalme Alternativo/genética , Secuencia de Aminoácidos , Animales , Proteínas de Unión al ADN/genética , Proteínas de Drosophila/genética , Histona Acetiltransferasas/genética , Datos de Secuencia Molecular , Unión Proteica/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Factores Asociados con la Proteína de Unión a TATA , Factor de Transcripción TFIID/genéticaRESUMEN
A novel factor featuring a composite AT hook/basic region-leucine zipper DNA-binding domain was isolated from Bombyx mori follicular cells. Screening of EST databases derived from a variety of metazoans revealed the exclusive presence of BmCbZ homologues in insect species. BmCbZ characteristic features and gene organization are discussed, in comparison to other known bZIP factors. We concordantly propose that this factor establishes a new insect-specific bZIP family. We further present the isolation of the silkmoth homologue of mammalian C/EBPgamma, BmC/EBPgamma, and in vitro evidence for its interaction with BmCbZ. The formation of a BmCbZ-BmC/EBPgamma heterodimer is a prerequisite for binding to specific C/EBP recognition sites on chorion gene promoters, most probably via both major and minor groove interactions.