RESUMEN
Adipocyte enhancer binding protein 2, as a component protein of Polycomb repressive complex (PRC2), is involved in the proliferation and migration of many tumor cells. However, its role in HCC is still unclear. In this study, we identify that AEBP2 was upregulated in HCC samples from the UALCAN and Kaplan-Meier Plotter database, which was correlated to the overall survival time of HCC patients. Real-time quantitative PCR and Western blotting confirmed that the expression of AEBP2 in HCC cells was higher than normal liver cells. After silencing AEBP2 in HepG2 and Huh-7 cells, the effects of the proliferation, apoptosis, migration and invasion were detected by colony formation, CCK-8, flow cytometry, scratch healing and Transwell chamber, respectively. Compared with the control group, down-regulation of AEBP2 expression inhibited the proliferation, migration and invasion in HepG2 and Huh-7 cells, as well as promoted apoptosis (P<0. 05). Immunofluorescence and Western blotting results showed that AEBP2 silencing inhibited epithelial-mesenchymal transformation (EMT) (P < 0. 05). Bioinformatics analysis showed that AEBP2 is involved the PI3K/Akt signaling pathway. Western blotting results confirmed that silencing AEBP2 down-regulated the expression levels of PI3K, p-AKT (S473), mTOR, MMP-2 and MMP-9 proteins (P<0. 05). In addition, the effects of AEBP2 silencing on HepG2 cells migration and invasion could be reversed by PI3K/Akt pathway agonist insulin-like Growth Factors (IGF-1) (P < 0. 01). In summary, our study showed that AEBP2 promoted the proliferation and migration of HCC cell by regulating PI3K/AKT pathway. This study provided a theoretical basis for the role of AEBP2 in HCC.
RESUMEN
AEBP2 is a zinc finger protein and a potential targeting protein for the mammalian Polycomb Repression Complex 2 (PRC2). The role of AEBP2 in the regulation of the migration and development of the neural crest cells through the PRC2-mediated epigenetic mechanism has been well-documented. However, whether AEBP2 plays a role in cancer and how to regulate AEBP2 itself remains largely unknown. Here, we show that genetic knockout of AEBP2 inhibited ovarian cancer cells proliferation and increased cisplatin sensitivity. Moreover, AEBP2 contains a non-canonical phosphodegron and is constantly targeted for ubiquitylation and proteasomal degradation by a SKP1-CUL1-F-box protein (SCF) ß-TrCP ubiquitin ligase complex. Failure to degrade AEBP2 conferred cisplatin resistance in ovarian cancer. Overall, this study reveals an oncogenic role of AEBP2 in ovarian cancer and provides a rationale to target ß-TRCP-AEBP2 axis in ovarian cancer that may be therapeutically beneficial.
Asunto(s)
Antineoplásicos/farmacología , Cisplatino/farmacología , Resistencia a Antineoplásicos/efectos de los fármacos , Neoplasias Ováricas/tratamiento farmacológico , Proteínas Represoras/metabolismo , Ubiquitinación , Proteínas con Repetición de beta-Transducina/metabolismo , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Ensayos de Selección de Medicamentos Antitumorales , Femenino , Células HEK293 , Humanos , Neoplasias Ováricas/metabolismo , Neoplasias Ováricas/patología , Proteínas Represoras/deficienciaRESUMEN
Polycomb repressive complex 2 (PRC2) is composed of EED, SUZ12, and EZH1/2 and mediates mono-, di-, and trimethylation of histone H3 at lysine 27. At least two independent subcomplexes exist, defined by their specific accessory proteins: PRC2.1 (PCL1-3, EPOP, and PALI1/2) and PRC2.2 (AEBP2 and JARID2). We show that PRC2.1 and PRC2.2 share the majority of target genes in mouse embryonic stem cells. The loss of PCL1-3 is sufficient to evict PRC2.1 from Polycomb target genes but only leads to a partial reduction of PRC2.2 and H3K27me3. Conversely, disruption of PRC2.2 function through the loss of either JARID2 or RING1A/B is insufficient to completely disrupt targeting of SUZ12 by PCLs. Instead, the combined loss of both PRC2.1 and PRC2.2 is required, leading to the global mislocalization of SUZ12. This supports a model in which the specific accessory proteins within PRC2.1 and PRC2.2 cooperate to direct H3K27me3 via both synergistic and independent mechanisms.
Asunto(s)
Cromatina/metabolismo , Histonas/metabolismo , Células Madre Embrionarias de Ratones/metabolismo , Complejo Represivo Polycomb 2/metabolismo , Procesamiento Proteico-Postraduccional , Animales , Sitios de Unión , Línea Celular Tumoral , Cromatina/genética , Humanos , Metilación , Ratones , Complejo Represivo Polycomb 1/genética , Complejo Represivo Polycomb 1/metabolismo , Complejo Represivo Polycomb 2/genética , Unión Proteica , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
Numerous molecular processes conduct epigenetic regulation of protein transcription to maintain cell specification. In this review, we discuss molecular mechanisms of the Polycomb group of proteins and its enzymatic role in epigenetics. More specifically, we focus on the Polycomb repressive complex 2 (PRC2) and the effects of its repressive marker. We have compiled information regarding the biological structure and how that impacts the stability of the complex. In addition, we examined functions of the individual core proteins of PRC2 in relation to the accessory proteins that interact with the complex. Lastly, we discuss the implications of unregulated and downregulated PRC2 activity in Alzheimer's disease and cancer and possible methods of treatment related to PRC2 regulation.
Asunto(s)
Neoplasias/metabolismo , Complejo Represivo Polycomb 2/metabolismo , Enfermedad de Alzheimer/metabolismo , Animales , Humanos , Complejo Represivo Polycomb 2/químicaRESUMEN
The maintenance of gene expression patterns during metazoan development is achieved, in part, by the actions of polycomb repressive complex 2 (PRC2). PRC2 catalyzes mono-, di-, and trimethylation of histone H3 at lysine 27 (H3K27), with H3K27me2/3 being strongly associated with silenced genes. We demonstrate that EZH1 and EZH2, the two mutually exclusive catalytic subunits of PRC2, are differentially activated by various mechanisms. Whereas both PRC2-EZH1 and PRC2-EZH2 are able to catalyze mono- and dimethylation, only PRC2-EZH2 is strongly activated by allosteric modulators and specific chromatin substrates to catalyze trimethylation of H3K27 in mouse embryonic stem cells (mESCs). However, we also show that a PRC2-associated protein, AEBP2, can stimulate the activity of both complexes through a mechanism independent of and additive to allosteric activation. These results have strong implications regarding the cellular requirements for and the accompanying adjustments in PRC2 activity, given the differential expression of EZH1 and EZH2 upon cellular differentiation.
Asunto(s)
Complejo Represivo Polycomb 2/metabolismo , Animales , Catálisis , Línea Celular , Cromatina/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteína Potenciadora del Homólogo Zeste 2/metabolismo , Células HEK293 , Histonas/metabolismo , Humanos , Lisina/metabolismo , Metilación , RatonesRESUMEN
The polycomb repressive complex 2 (PRC2) consists of core subunits SUZ12, EED, RBBP4/7, and EZH1/2 and is responsible for mono-, di-, and tri-methylation of lysine 27 on histone H3. Whereas two distinct forms exist, PRC2.1 (containing one polycomb-like protein) and PRC2.2 (containing AEBP2 and JARID2), little is known about their differential functions. Here, we report the discovery of a family of vertebrate-specific PRC2.1 proteins, "PRC2 associated LCOR isoform 1" (PALI1) and PALI2, encoded by the LCOR and LCORL gene loci, respectively. PALI1 promotes PRC2 methyltransferase activity in vitro and in vivo and is essential for mouse development. Pali1 and Aebp2 define mutually exclusive, antagonistic PRC2 subtypes that exhibit divergent H3K27-tri-methylation activities. The balance of these PRC2.1/PRC2.2 activities is required for the appropriate regulation of polycomb target genes during differentiation. PALI1/2 potentially link polycombs with transcriptional co-repressors in the regulation of cellular identity during development and in cancer.
Asunto(s)
Complejo Represivo Polycomb 2/genética , Proteínas Represoras/genética , Vertebrados/genética , Secuencia de Aminoácidos , Animales , Diferenciación Celular/genética , Línea Celular , Células HEK293 , Histonas/genética , Humanos , Metilación , Metiltransferasas/genética , Ratones , Neoplasias/genética , Alineación de SecuenciaRESUMEN
Developmentally regulated accessory subunits dictate PRC2 function. Here, we report the crystal structures of a 120 kDa heterotetrameric complex consisting of Suz12, Rbbp4, Jarid2, and Aebp2 fragments that is minimally active in nucleosome binding and of an inactive binary complex of Suz12 and Rbbp4. Suz12 contains two unique structural platforms that define distinct classes of PRC2 holo complexes for chromatin binding. Aebp2 and Phf19 compete for binding of a non-canonical C2 domain of Suz12; Jarid2 and EPOP occupy an overlapped Suz12 surface required for chromatin association of PRC2. Suz12 and Aebp2 progressively block histone H3K4 binding to Rbbp4, suggesting that Rbbp4 may not be directly involved in PRC2 inhibition by the active H3K4me3 histone mark. Nucleosome binding enabled by Jarid2 and Aebp2 is in part accounted for by the structures, which also reveal that disruption of the Jarid2-Suz12 interaction may underlie the disease mechanism of an oncogenic chromosomal translocation of Suz12.
Asunto(s)
Complejo Represivo Polycomb 2/química , Humanos , Proteínas de Neoplasias , Nucleosomas/química , Nucleosomas/genética , Nucleosomas/metabolismo , Complejo Represivo Polycomb 2/genética , Complejo Represivo Polycomb 2/metabolismo , Dominios Proteicos , Estructura Cuaternaria de Proteína , Proteínas Represoras/química , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Proteína 4 de Unión a Retinoblastoma/química , Proteína 4 de Unión a Retinoblastoma/genética , Proteína 4 de Unión a Retinoblastoma/metabolismo , Factores de TranscripciónRESUMEN
The Polycomb repressive complexes PRC1 and PRC2 are key mediators of heritable gene silencing in multicellular organisms. Here, we characterise AEBP2, a known PRC2 co-factor which, in vitro, has been shown to stimulate PRC2 activity. We show that AEBP2 localises specifically to PRC2 target loci, including the inactive X chromosome. Proteomic analysis confirms that AEBP2 associates exclusively with PRC2 complexes. However, analysis of embryos homozygous for a targeted mutation of Aebp2 unexpectedly revealed a Trithorax phenotype, normally linked to antagonism of Polycomb function. Consistent with this, we observe elevated levels of PRC2-mediated histone H3K27 methylation at target loci in Aebp2 mutant embryonic stem cells (ESCs). We further demonstrate that mutant ESCs assemble atypical hybrid PRC2 subcomplexes, potentially accounting for enhancement of Polycomb activity, and suggesting that AEBP2 normally plays a role in defining the mutually exclusive composition of PRC2 subcomplexes.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Células Madre Embrionarias/citología , Células Madre Embrionarias/metabolismo , Proteínas Nucleares/metabolismo , Complejo Represivo Polycomb 2/metabolismo , Proteómica/métodos , Animales , Línea Celular , Proteínas de Unión al ADN/genética , Femenino , Histonas/metabolismo , Ratones , Mutación/genética , Proteínas Nucleares/genética , Complejo Represivo Polycomb 2/genética , Proteínas RepresorasRESUMEN
The Polycomb group (PcG) of proteins form chromatin-binding complexes with histone-modifying activity. The two main PcG repressive complexes studied (PRC1 and PRC2) are generally associated with chromatin in its repressed state. PRC2 is responsible for methylation of histone H3 at lysine 27 (H3K27me3), an epigenetic mark that is linked with numerous biological processes, including development, adult homeostasis and cancer. The core canonical complex PRC2, which contains the EZH1/2, SUZ12 and EED proteins, may be extended and functionally manipulated through interactions with several other proteins. In this review, we focus on these PRC2-associated proteins. As PRC2 functions are diverse, the variability conferred by these sub-stoichiometrically associated members may help to understand specific changes in PRC2 activity, chromatin recruitment and distribution required for gene repression.
Asunto(s)
Enfermedad , Proteínas del Grupo Polycomb/fisiología , Células Madre/citología , Animales , Humanos , Metilación , Proteínas del Grupo Polycomb/metabolismo , Células Madre/metabolismoRESUMEN
Aebp2 encodes an evolutionarily conserved zinc finger protein that has not been well studied so far, yet recent studies indicated that this gene is closely associated with the Polycomb Repressive Complex 2 (PRC2). Thus, the current study characterized the basic aspects of this gene, including alternative promoters and protein isoforms. According to the results, Aebp2 is controlled through three alternative promoters, deriving three different transcripts encoding the embryonic (32 kDa) and somatic (52 kDa) forms. Chromatin Immuno-Precipitation (ChIP) experiments revealed that AEBP2 binds to its own promoter as well as the promoters of Jarid2 and Snai2. While the embryonic form acts as a transcriptional repressor for Snai2, the somatic form functions as a transcriptional activator for Jarid2, Aebp2 and Snai2. Cell migration assays also demonstrated that the Aebp2 somatic form has an enhancing activity in cell migration. This is consistent with the functional association of Aebp2 with migratory neural crest cells. These results suggest that the two protein isoforms of AEBP2 may have opposite functions for the PcG target genes, and may play significant roles in cell migration during development.
Asunto(s)
Movimiento Celular/fisiología , Proteínas de Unión al ADN/metabolismo , Proteínas Nucleares/metabolismo , Activación Transcripcional , Animales , Secuencia de Bases , Regulación del Desarrollo de la Expresión Génica , Ratones , Datos de Secuencia Molecular , Cresta Neural/metabolismo , Complejo Represivo Polycomb 2/metabolismo , Regiones Promotoras Genéticas , Isoformas de Proteínas/metabolismo , Proteínas Represoras/metabolismo , Factores de Transcripción de la Familia Snail , Factores de Transcripción/metabolismoRESUMEN
Two histone marks, H3K27me3 and H3K9me3, are well known for their repressive roles in the genic and nongenic regions of metazoan genomes. Several protein complexes are known to be responsible for generating these marks, including polycomb repression complex 2 and several H3K9 methylases. Recent studies have shown that the targeting of these histone-modifying complexes within mammalian genomes may be mediated through several DNA-binding proteins, including AEBP2, JARID2, and YY1. In this review, we discuss the potential targeting mechanisms in light of the recent results that have been derived from genome-wide chromatin immunoprecipitation sequencing data and the in vivo functions of these two histone marks in light of the results derived from mouse and human genetic studies.