RESUMEN

Congenital diaphragmatic hernia (CDH) is a severe birth defect characterized by a defect in the diaphragm with pulmonary hypoplasia and postnatal pulmonary hypertension. Approximately 50% of CDH cases are associated with other non-pulmonary congenital anomalies (so called non-isolated CDH) and in 5-10% of cases there is a chromosomal etiology. The majority of CDH cases are detected prenatally. In some cases prenatal chromosome analysis reveals a causative chromosomal anomaly, most often aneuploidy. Deletion of 15q26 is the most frequently described structural chromosomal aberration in patients with non-isolated CDH. In this paper we report on two patients with a deletion of 15q26 and phenotypes similar to other patients with CDH caused by 15q26 deletions. This phenotype consists of intra-uterine growth retardation, left-sided CDH, cardiac anomalies and characteristic facial features, similar to those seen in Fryns syndrome. We propose that when this combination of birth defects is identified, either pre- or postnatally, further investigations to confirm or exclude a deletion of 15q26 are indicated, since the diagnosis of this deletion will have major consequences for the prognosis and, therefore, can affect decision making.

Asunto(s)

Deleción Cromosómica , Cromosomas Humanos Par 15 , Hernia Diafragmática/diagnóstico por imagen , Ultrasonografía Prenatal , Bandeo Cromosómico , Resultado Fatal , Femenino , Hernia Diafragmática/genética , Hernia Diafragmática/terapia , Hernias Diafragmáticas Congénitas , Humanos , Cariotipificación

RESUMEN

Fli-2 is a common site of proviral integration in multistage erythroleukemia cells induced by Friend murine leukemia virus (F-MuLV) or the polycythemia strain of Friend leukemia virus (FV-P). Previously, we reported that integration of Friend virus into the Fli-2 locus in CB3, an erythroleukemia cell line that harbors a homozygous inactivation of the Fli-2 locus, results in the loss of expression of two genes encoding the 45-kDa subunit of the erythroid-specific nuclear factor p45 NFE2 and the splicing factor HnRNP A1. Here, we report the identification of a third gene, Heterochromatin protein 1 (HP1alpha, also known as CBX5), which is located downstream of HnRNP A1, and p45 NFE2. Northern blot analysis revealed that the expression of HP1alpha, along with p45 NFE2 and HnRNP A1, is either undetectable or substantially reduced in CB3 cells, suggesting that HP1alpha expression is also regulated by proviral insertion within the Fli-2 locus in CB3 cells. Because p45 NFE2 was previously mapped to mouse chromosome 15, our results demonstrate that HP1alpha and HnRNP A1 are also located on mouse chromosome 15 and that the p45 NFE2, HnRNP A1, and HP1alpha genes are arranged contiguously. Contiguous arrangement of these three genes was also detected in man; this consequently localizes HP1alpha to human chromosome band 12q13.

Asunto(s)

Proteínas Cromosómicas no Histona/genética , Cromosomas Humanos Par 12/genética , Proteínas de Unión al ADN/genética , Heterocromatina/genética , Ribonucleoproteína Heterogénea-Nuclear Grupo A-B , Proteínas Proto-Oncogénicas , Ribonucleoproteínas/genética , Supresión Genética , Transactivadores/genética , Factores de Transcripción/genética , Animales , Homólogo de la Proteína Chromobox 5 , Factores de Unión al ADN Específico de las Células Eritroides , Orden Génico/genética , Ribonucleoproteína Nuclear Heterogénea A1 , Ribonucleoproteínas Nucleares Heterogéneas , Humanos , Masculino , Ratones , Datos de Secuencia Molecular , Subunidad p45 del Factor de Transcripción NF-E2 , Proteína Proto-Oncogénica c-fli-1 , ARN Nuclear Heterogéneo/genética , Proteínas de Unión al ARN/genética , Mapeo Restrictivo

RESUMEN

In previous studies, we identified a common site of retroviral integration designated Fli-2 in Friend murine leukemia virus (F-MuLV)-induced erythroleukemia cell lines. Insertion of F-MuLV at the Fli-2 locus, which was associated with the loss of the second allele, resulted in the inactivation of the erythroid cell- and megakaryocyte-specific gene p45(NFE2). Frequent disruption of p45(NFE2) due to proviral insertion suggests a role for this transcription factor in the progression of Friend virus-induced erythroleukemias. To assess this possibility, erythroleukemia was induced by F-MuLV in p45(NFE2) mutant mice. Since p45(NFE2) homozygous mice mostly die at birth, erythroleukemia was induced in +/- and +/+ mice. We demonstrate that +/- mice succumb to the disease moderately but significantly faster than +/+ mice. In addition, the spleens of +/- mice were significantly larger than those of +/+ mice. Of the 37 tumors generated from the +/- and +/+ mice, 10 gave rise to cell lines, all of which were derived from +/- mice. Establishment in culture was associated with the loss of the remaining wild-type p45(NFE2) allele in 9 of 10 of these cell lines. The loss of a functional p45(NFE2) in these cell lines was associated with a marked reduction in globin gene expression. Expression of wild-type p45(NFE2) in the nonproducer erythroleukemic cells resulted in reduced cell growth and restored the expression of globin genes. Similarly, the expression of p45(NFE2) in these cells also slows tumor growth in vivo. These results indicate that p45(NFE2) functions as an inhibitor of erythroid cell growth and that perturbation of its expression contributes to the progression of Friend erythroleukemia.

Asunto(s)

Proteínas de Unión al ADN/metabolismo , Virus de la Leucemia Murina de Friend/fisiología , Leucemia Eritroblástica Aguda/patología , Leucemia Eritroblástica Aguda/virología , Factores de Transcripción/metabolismo , Animales , Animales Recién Nacidos , División Celular , Células Clonales/metabolismo , Células Clonales/patología , Células Clonales/virología , Proteínas de Unión al ADN/genética , Progresión de la Enfermedad , Factores de Unión al ADN Específico de las Células Eritroides , Eliminación de Gen , Regulación Neoplásica de la Expresión Génica , Genotipo , Globinas/genética , Leucemia Eritroblástica Aguda/genética , Leucemia Eritroblástica Aguda/metabolismo , Ratones , Ratones Endogámicos , Ratones Noqueados , Subunidad p45 del Factor de Transcripción NF-E2 , Factores de Transcripción/genética , Transfección , Células Tumorales Cultivadas

RESUMEN

We have recently isolated the erythroleukemic cell line, HB60-5, that proliferates in the presence of erythropoietin (Epo) and stem cell factor (SCF), but undergoes terminal differentiation in the presence of Epo alone. Ectopic expression of the ets related transcription factor Fli-1 in these cells resulted in the establishment of the Epo-dependent cell line HB60-ED that proliferates in the presence of Epo. In this study, we utilized these two cell lines to examine the signal transduction pathways that are activated in response to Epo and SCF stimulation. We demonstrate that Epo, but not SCF, phosphorylates STAT-5 in both HB60-5 and HB60-ED cells. Interestingly, SCF activates the Shc/ras pathway in HB60-5 cells while Epo does not. However, both Epo and SCF are capable of activating the Shc/ras pathway in HB60ED cells. Furthermore, enforced expression of gp55 in HB60-5 cells by means of infection with the Spleen Focus Forming virus-P (SFFV-P), confers Epo independent growth, which is associated with the up-regulation of Fli-1. Activation of the Shc/ras pathway is readily detected in gp55 expressing cells in response to both Epo and SCF, and is associated with a block in STAT-5B tyrosine phosphorylation. These results suggest that STAT-5 activation, in the absence of Shc/ras activation, plays a role in erythroid differentiation. Moreover, Fli-1 is capable of switching Epo-induced differentiation to Epo-induced proliferation, suggesting that this ets factor regulated genes whose products modulate the Epo-Epo-R signal transduction pathway.

Asunto(s)

Proteínas Adaptadoras Transductoras de Señales , Proteínas Adaptadoras del Transporte Vesicular , Eritropoyetina/metabolismo , Virus de la Leucemia Murina de Friend , Leucemia Eritroblástica Aguda/metabolismo , Proteínas de la Leche , Proteínas Proto-Oncogénicas , Transducción de Señal , Animales , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/fisiología , División Celular/efectos de los fármacos , División Celular/fisiología , Proteínas de Unión al ADN/metabolismo , Eritropoyesis/fisiología , Eritropoyetina/farmacología , Humanos , Leucemia Eritroblástica Aguda/tratamiento farmacológico , Ratones , Ratones Endogámicos BALB C , Fosfatidilinositol 3-Quinasas/metabolismo , Fosforilación , Proteínas/metabolismo , Proteína Proto-Oncogénica c-fli-1 , Receptores de Eritropoyetina/metabolismo , Factor de Transcripción STAT5 , Proteínas Adaptadoras de la Señalización Shc , Proteína Transformadora 1 que Contiene Dominios de Homología 2 de Src , Factor de Células Madre/metabolismo , Factor de Células Madre/farmacología , Transactivadores/metabolismo , Células Tumorales Cultivadas , Proteínas del Envoltorio Viral/metabolismo , Proteínas ras/metabolismo

RESUMEN

Karyotype-phenotype correlations of common trisomy mosaicism prenatally diagnosed via amniocentesis was reviewed in 305 new cases from a collaboration of North American cytogenetic laboratories. Abnormal outcome was noted in 10/25 (40%) cases of 47,+13/46, 17/31 (54%) cases of 47,+18/46, 10/152 (6.5%) cases of 47,+20/46, and in 49/97 (50%) cases of 47,+21/46 mosaicism. Risk of abnormal outcome in pregnancies with less than 50% trisomic cells and greater than 50% trisomic cells were: 26% (4/15) versus 60% (6/10) for 47,+13/46, 52% (11/21) versus 75% (6/8) for 47,+18/46, 4.5% (6/132) versus 20% (4/20) 47,+20/46, and 45% (27/60) versus 59% (22/37) for 47,+21/46. Phenotypically normal liveborns were observed with mean trisomic cell lines of 9.3% for 47,+13/46, 8.6% for 47,+18/46, 27% for 47, +20/46, and 17% for 47,+21/46. Cytogenetic confirmation rates were 46% (6/13 cases) for 47,+13/46 mosaicism, 66% (8/12 cases) for 47, +18/46, 10% (10/97 cases) for 47,+20/46, and 44% (24/54 cases) for 47,+21/46. There were higher confirmation rates in pregnancies with abnormal versus normal outcome: 50% versus 44% for 47,+13/46 mosaicism, 100% versus 33% for 47,+18/46, 66% versus 7% for 47, +20/46, and 55% versus 40% for 47,+21/46. Repeat amniocentesis is not helpful in predicting clinical outcome. It may be considered when there is insufficient number of cells or cultures to establish a diagnosis. Fetal blood sampling may have a role in mosaic trisomy 13, 18, and 21 as the risk for abnormal outcome increases with positive confirmation: 1/5 (20%) normal cases versus 5/8 (62%) abnormal cases. High resolution ultrasound examination(s) is recommended for clinical correlation and to facilitate genetic counselling.

Asunto(s)

Cromosomas Humanos Par 13 , Cromosomas Humanos Par 18 , Cromosomas Humanos Par 20 , Síndrome de Down/genética , Mosaicismo , Trisomía , Anomalías Múltiples/genética , Amniocentesis , Líquido Amniótico/citología , Femenino , Muerte Fetal/genética , Retardo del Crecimiento Fetal/genética , Cardiopatías Congénitas/genética , Humanos , Cariotipificación , Fenotipo , Embarazo , Resultado del Embarazo

RESUMEN

Twenty-eight laboratories evaluated a new fluorescence in situ hybridization (FISH) strategy for chronic myeloid leukemia. In a three-part study, bcr/abl1 D-FISH probes were used to study bone marrow specimens. First, laboratories familiarized themselves with the strategy by applying it to known normal and abnormal specimens. Then, collectively the laboratories studied 20 normal and 20 abnormal specimens blindly and measured workload. Finally, each laboratory and two experts studied six serial dilutions with 98-0% abnormal nuclei. Using the reported normal cutoff of < 1% abnormal nuclei, participants reported no false-negative cases and 15 false-positive cases (1-6.6% abnormal nuclei). Results provided by participants for serial dilutions approximated the expected percentages of abnormal nuclei, but those from the experts exhibited greater precision. The clinical sensitivity, precision, nomenclature, workload, recommendations for training, and quality assurance in methods using D-FISH in clinical practice are discussed.

Asunto(s)

Técnicas de Laboratorio Clínico/normas , Proteínas de Fusión bcr-abl/genética , Hibridación Fluorescente in Situ , Leucemia Mielógena Crónica BCR-ABL Positiva/diagnóstico , Médula Ósea/patología , Colorantes Fluorescentes , Humanos , Hibridación Fluorescente in Situ/instrumentación , Hibridación Fluorescente in Situ/métodos , Hibridación Fluorescente in Situ/normas , Leucemia Mielógena Crónica BCR-ABL Positiva/genética , Leucemia Mielógena Crónica BCR-ABL Positiva/patología , Control de Calidad , Sensibilidad y Especificidad , Carga de Trabajo

RESUMEN

Erythropoietin (Epo) is a major regulator of erythropoiesis that alters the survival, proliferation, and differentiation of erythroid progenitor cells. The mechanism by which these events are regulated has not yet been determined. Using HB60, a newly established erythroblastic cell line, we show here that Epo-induced terminal erythroid differentiation is associated with a transient downregulation in the expression of the Ets-related transcription factor Fli-1. Constitutive expression of Fli-1 in HB60 cells, similar to retroviral insertional activation of Fli-1 observed in Friend murine leukemia virus (F-MuLV)-induced erythroleukemia, blocks Epo-induced differentiation while promoting Epo-induced proliferation. These results suggest that Fli-1 modulates the response of erythroid cells to Epo. To understand the mechanism by which Fli-1 regulates erythropoiesis, we searched for downstream target genes whose expression is regulated by this transcription factor. Here we show that the retinoblastoma (Rb) gene, which was previously shown to be involved in the development of mature erythrocytes, contains a Fli-1 consensus binding site within its promoter. Fli-1 binds to this cryptic Ets consensus site within the Rb promoter and transcriptionally represses Rb expression. Both the expression level and the phosphorylation status of Rb are consistent with the response of HB60 cells to Epo-induced terminal differentiation. We suggest that the negative regulation of Rb by Fli-1 could be one of the critical determinants in erythroid progenitor cell differentiation that is specifically deregulated during F-MuLV-induced erythroleukemia.

Asunto(s)

Proteínas de Unión al ADN/fisiología , Células Precursoras Eritroides/fisiología , Eritropoyetina/fisiología , Genes de Retinoblastoma/genética , Proteínas Proto-Oncogénicas , Transactivadores/fisiología , Transcripción Genética , Animales , Northern Blotting , Ciclo Celular , Diferenciación Celular , División Celular , Cromatina/metabolismo , Electroforesis en Gel de Poliacrilamida , Immunoblotting , Ratones , Ratones Endogámicos BALB C , Modelos Genéticos , Neoplasias Experimentales , Oligonucleótidos Antisentido , Pruebas de Precipitina , Regiones Promotoras Genéticas , Proteína Proto-Oncogénica c-fli-1 , Proteínas Proto-Oncogénicas c-kit/fisiología , Proteínas Recombinantes de Fusión , Factor de Células Madre/fisiología , Factores de Tiempo , Transfección , Células Tumorales Cultivadas

RESUMEN

We report on a girl with duplication of 6q22.32 --> qter and microcephaly, frontal bossing, facial anomalies, and webbed neck. She has congenital heart disease, renal hypoplasia, and hearing loss along with severe developmental delay. Published reports of seven other patients are reviewed and compared. The most frequent anomalies include microcephaly, abnormal face, webbed neck, congenital heart disease, limb contractures, and developmental delay.

Asunto(s)

Anomalías Múltiples/genética , Cromosomas Humanos Par 14 , Cromosomas Humanos Par 6 , Translocación Genética , Femenino , Humanos , Lactante , Fenotipo

RESUMEN

Twenty-six laboratories used X and Y chromosome probes and the same procedures to process and examine 15,600 metaphases and 49,400 interphases from Phaseolus vulgaris-leucoagglutinin (PHA)-stimulated lymphocytes. In Part I, each laboratory scored 50 metaphases and 200 interphases from a normal male and a normal female from its own practice. In Part II, each laboratory scored 50 metaphases and 200 interphases on slides prepared by a central laboratory from a normal male and a normal female and three mixtures of cells from the male and female. In Part III, each laboratory scored 50 metaphases (in samples of 5, 10, 15, and 20) and 100 interphases (in samples of 5, 10, 15, 20, and 50) on new, coded slides of the same specimens used in Part II. Metaphases from male specimens were scored as 98-99% XY with no XX cells, and 97-98% of interphases were scored as XY with 0.04% XX cells. Metaphases from female specimens were scored as 96-97% XX with 0.03% XY cells, and 94-96% of interphases were scored as XX with 0.05% XY cells. Considering the data as a model for any probe used with fluorescence in situ hybridization (FISH), a statistical approach assessing the impact of analytical sensitivity on the numbers of observations required to assay for potential mosaicisms and chimerisms is discussed. The workload associated with processing slides and scoring 50 metaphases and 200 interphases using FISH averaged 27.1 and 28.6 minutes, respectively. This study indicates that multiple laboratories can test/develop guidelines for the rapid, efficacious, and cost-effective integration of FISH into clinical service.

Asunto(s)

Sondas de ADN , Hibridación Fluorescente in Situ/métodos , Interfase , Cromosoma X , Cromosoma Y , Citogenética/normas , Femenino , Humanos , Hibridación Fluorescente in Situ/instrumentación , Laboratorios/normas , Activación de Linfocitos , Linfocitos/citología , Masculino , Metafase , Fitohemaglutininas , Control de Calidad , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Carga de Trabajo

RESUMEN

In order to determine the significance of trisomy mosaicism of an autosome other than chromosomes 13, 18, 20, and 21, 151 such cases diagnosed prenatally through amniocentesis were reviewed. These rare trisomy mosaicism cases include 54 from 17 cytogenetic laboratories, 34 from a previous North American mosaicism survey, and 63 from published reports. All were cases of true mosaicism with information available on pregnancy outcome, and with no evidence of biased ascertainment. There were 11 cases of 46/47, +2; 2 of 46/47, +3; 2 of 46/47, +4; 5 of 46/47, +5; 3 of 46/47, +6; 8 of 46/47, +7; 14 of 46/47, +8; 25 of 46/47, +9; 2 of 46/47, +11; 23 of 46/47, +12; 5 of 46/47, +14; 11 of 46/47, +15; 21 of 46/47, +16; 7 of 46/47, +17; 1 of 46/47, +19; and 11 of 46/47, +22. As to the risk of an abnormal outcome, the data showed a very high risk (> 60 per cent) for 46/47, +2, 46/47, +16, and 46/47, +22; a high risk (40-59 per cent) for 46/47, +5, 46/47, +9, 46/47, +14, and 46/47, +15; a moderately high risk (20-39 per cent) for 46/47, +12; a moderate risk (up to 19 per cent) for 46/47, +7 and 46/47, +7 and 46/47, +8; a low risk for 46/47, +17; and an undetermined risk, due to lack of cases, for the remaining autosomal trisomy mosaics. Most cases were evaluated at birth or at termination, so subtle abnormalities may have escaped detection and developmental retardation was not evaluated at all. Comparison of the phenotypes of prenatally diagnosed abnormal cases and postnatally diagnosed cases with the same diagnosis showed considerable concordance. Since the majority of anomalies noted are prenatally detectable with ultrasound, an ultrasound examination should be performed in all prenatally diagnosed cases. In cytogenetic confirmation studies, the data showed much higher confirmation rates in cases with abnormal outcomes than in cases with normal outcomes [81 per cent vs. 55 per cent for fibroblasts (from skin, fetal tissue, and/or cord); 88 per cent vs. 46 per cent for placental cells; 22 per cent vs. 10 per cent for blood cells]. The confirmation rate reached 85 per cent when both fibroblasts and placental tissues were studied in the same case (with trisomic cells found in one or the other, or both). Therefore, one must emphasize that both fibroblasts and placental tissues should be studied. Except for 46/47, +8 and 46/47, +9, PUBS is of limited value for prenatal diagnosis of rate trisomy mosaicism. DNA studies for UPD are suggested for certain chromosomes with established imprinting effects, such as chromosomes 7, 11, 14, and 15, and perhaps for chromosomes 2 and 16, where imprinting effects are likely.

Asunto(s)

Líquido Amniótico/citología , Aberraciones Cromosómicas/embriología , Mosaicismo/genética , Trisomía/genética , Adolescente , Adulto , Amniocentesis , Aberraciones Cromosómicas/diagnóstico , Aberraciones Cromosómicas/genética , Aberraciones Cromosómicas/patología , Trastornos de los Cromosomas , Femenino , Humanos , Cariotipificación , Masculino , Persona de Mediana Edad , Mosaicismo/diagnóstico , Mosaicismo/patología , Fenotipo , Embarazo , Resultado del Embarazo , Trisomía/diagnóstico , Trisomía/patología

RESUMEN

Terminase, the DNA packaging enzyme of phage lambda is an ATP-stimulated, site-specific endonuclease comprising the products of lambda genes Nu1 and A. The interaction of terminase with its specific DNA substrate cos was studied by footprinting. cos (the DNA segment R4-cosN-R3R2R1), situated at the chromosomal junctions in a concatemer, consists of a nicking domain (cosN) where terminase nicks DNA to regenerate the 12-base cohesive ends of the mature lambda chromosome and a binding domain (cosB) that includes four 16-base-pair repeat sequences, R1, R2 and R3 to the right of cosN and R4 (now called cosQ and not, in strict definition, part of cosB) to the left of cosN. We show that terminase molecules bind asymmetrically to the two ends of the chromosome. Binding to the right of cosN is stimulated by ATP, whereas binding to the left of cosN is strictly dependent upon ATP. When cosN is deleted and ATP is withheld, terminase molecules bind exclusively to the R3, R2 and R1 sites via their gpNu1 subunits. An invariant R-site GG doublet is protected from methylation in both R3 and R2, showing the location of major-groove close contacts upon binding. Terminase's interactions with DNAs that include all of cos are more extensive and are influenced by ATP; not only are the R sites protected, but so is the DNA between them, as well as cosN, the cosN-R3 region, R4 and sequences to the left of R4. The pattern suggests an highly organized protein-DNA continuum involving several terminase molecules and several hundred base-pairs of DNA, suitably named the termisome. Evidence is given that this assembly is dependent on the interaction of ATP with the gpA subunit of terminase.

Asunto(s)

Bacteriófago lambda/metabolismo , ADN Viral/metabolismo , Proteínas de Unión al ADN/metabolismo , Endodesoxirribonucleasas/metabolismo , Adenosina Trifosfato/metabolismo , Marcadores de Afinidad , Secuencia de Bases , Sitios de Unión , Metilación , Datos de Secuencia Molecular , Conformación de Ácido Nucleico , Proteínas Virales/metabolismo

RESUMEN

Partial deletion of the short arm of chromosome 9 (p24-->pter) and partial duplication of the long arm of chromosome 5 (q32-->qter) were observed in an abnormal boy who died at age 8 weeks of a complex cyanotic cardiac defect. He also had minor anomalies, sagittal craniosynostosis, triphalangeal thumbs, hypospadias, and a bifid scrotum. Two other infants with similar cytogenetic abnormalities were described previously. These patients had severe congenital heart defect, genitourinary anomalies, broad nasal bridge, low hairline, apparently low-set ears, short neck, and triphalangeal thumbs, in common with our patient. We suggest that combined monosomy 9p23,24-->pter and trisomy 5q31,32-->qter may constitute a clinically recognizable syndrome.

Asunto(s)

Anomalías Múltiples/genética , Cromosomas Humanos Par 5 , Cromosomas Humanos Par 9 , Cardiopatías Congénitas/genética , Monosomía , Trisomía , Autopsia , Bandeo Cromosómico , Mapeo Cromosómico , Humanos , Recién Nacido , Cariotipificación , Masculino , Síndrome

RESUMEN

The terminase enzyme of phage lambda is a site-specific endonuclease that nicks DNA concatemers to regenerate the 12 nucleotide cohesive ends of the mature chromosome. The enzyme's DNA target, cos, consists of a nicking domain, cosN, and a binding domain, cosB. cosB, situated to the right of cosN, comprises three 16 bp repeat sequences, R1, R2 and R3. A similar sequence, R4, is present to the left of cosN. It is shown here that terminase has an intrinsic specificity for cosN which is independent of the R sites. The interaction with cosN is mediated by binding to target sites that include 12 bp on the 5', and 2-7 bp on the 3' side of the nick. Of the four R sites, only R3 is required for the proper formation of ends. When R3 is present, an ATP-charged terminase system correctly catalyzes the production of staggered nicks in cosN, at sites N1 and N2 on the bottom and top strands, respectively. When ATP is omitted, the bottom strand is nicked incorrectly, at the site Nx, 8 bp to the left of N1. If R3 is removed or disabled by a point mutation, nicking in cosN becomes dependent upon ATP but, even in the presence of ATP, bottom strand nicking is divided between sites N1, the correct site, and Nx, the incorrect one. Thus, R3 is an important regulatory element and must reside in cis in respect to cosN. Furthermore, cosN substrates bearing point mutations at N1 and N2 are nicked at sites Nx and Ny, 8 bp to the left of N1 and N2, respectively. When R3 is present and ATP is added, nicking is redirected to the N1 and N2 positions despite the mutations present. Thus, terminase binding to R3, on one side of cosN, regulates the rotationally symmetric nicking reactions on the bottom and top strands within cosN.

Asunto(s)

Adenosina Trifosfato/metabolismo , Bacteriófago lambda/enzimología , ADN Circular/metabolismo , ADN Viral/metabolismo , Endodesoxirribonucleasas/metabolismo , Bacteriófago lambda/genética , Bacteriófago lambda/crecimiento & desarrollo , Secuencia de Bases , Daño del ADN , ADN Circular/genética , ADN Recombinante , ADN Viral/genética , Datos de Secuencia Molecular , Mutación Puntual , Unión Proteica , Secuencias Repetitivas de Ácidos Nucleicos , Especificidad por Sustrato

RESUMEN

lambda terminase is an ATP-interactive, site-specific endonuclease comprising the products of lambda genes Nu1 and A. Terminase binds to cos, at the junction of two chromosomes in a concatemer, catalyzes cos cleavage and initiates the packaging of lambda DNA into proheads. cos consists of a nicking domain, cosN, where terminase cleaves to regenerate the 12 nucleotide cohesive ends of mature lambda chromosomes and a binding domain, cosB, where terminase binds to 16 bp repeat sequences called R3, R2 and R1. Evidence is presented that terminase is a single-strand endonuclease that can nick DNA by one of two mechanisms, both of which require ATP. (i) When bound to any R site, terminase nicks the strand which, within that R site, is purine-rich; the position of this nick is 47 +/- 2 nucleotides away from the mid-point of that R site, measured in the 3' direction; (ii) enzymes that are not bound to R sites nick DNA within certain specific sequences that resemble cosN half sites. These two modes of action are nicely combined for the R3-bound protomer that nicks the bottom strand at position N1 in cosN since the interval between N1 and the R3 midpoint is 47 nucleotides. Within cosN, the bottom and top strand nicks are generated by a rigid protein couple with a 2-fold rotational symmetry. The location of both of these nicks, however, is gauged asymmetrically from R3, 47 nucleotides away. Again, R1 and R2 are separated by 47 bp and orient bound protomers towards each other but, unless the DNA between these R sites is lengthened, the enzymes do not nick, indicating an inhibitory gpA-gpNu1 apposition.

Asunto(s)

Bacteriófago lambda/enzimología , ADN Viral/metabolismo , Endodesoxirribonucleasas/metabolismo , Secuencia de Bases , Sitios de Unión , Daño del ADN , Modelos Biológicos , Datos de Secuencia Molecular , Unión Proteica , Secuencias Repetitivas de Ácidos Nucleicos , Eliminación de Secuencia , Especificidad por Sustrato

RESUMEN

A case of congenital acute lymphoblastic leukemia (ALL) displayed an X;6 translocation. This is the third reported case of ALL with an X;6 translocation. In addition, two of the three ALL cases occurred during infancy, at ages 2 months and newborn, and both translocations involved the band q15-16 region of chromosome 6. Anomalies of the long arm of chromosome 6, mainly interstitial and terminal deletions, have been reported as a recurrent karyotypic event in a significant number of ALL cases. The molecular basis and propensity of an X;6 rearrangement in this case of congenital ALL is unclear and merits further investigation. The similarities in this case and the other infant ALL case cited suggest that an X;6 rearrangement with a breakpoint in bands q15-16 of chromosome 6 is characteristic of a form of congenital ALL.

Asunto(s)

Cromosomas Humanos Par 6 , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Translocación Genética , Cromosoma X , Médula Ósea/patología , Células Cultivadas , Bandeo Cromosómico , Humanos , Recién Nacido , Cariotipificación , Masculino , Leucemia-Linfoma Linfoblástico de Células Precursoras/congénito , Leucemia-Linfoma Linfoblástico de Células Precursoras/patología

RESUMEN

We report on an infant boy with duplication of part of 16p and partial deficiency of 9p: 46,XY, -9, + der(9)t(9;16)(p24;p13.1)mat. The child has the typical phenotype of dup(16p) even though the extra piece of 16p is small (16p13.1----pter). Manifestations include severe developmental delay, rounded face, sparse hair, ear anomalies, hypertelorism, cleft soft palate, a thin vermilion border of the upper lip, and left renal dysgenesis. We review 16p duplications.

Asunto(s)

Anomalías Múltiples/genética , Aberraciones Cromosómicas/genética , Cromosomas Humanos Par 16/ultraestructura , Cromosomas Humanos Par 9/ultraestructura , Trisomía , Trastornos de los Cromosomas , Humanos , Lactante , Masculino

RESUMEN

We describe a premature male infant with an interstitial deletion of 7q [46,XY,del(7) (pter----q21.3::q31.3----qter]. Manifestations include absence of lower limbs, unilateral ectrodactyly, facial anomalies, gingival hyperplasia, feeding problems, and atrial septal defect. Chromosome 7 deletions of the q21.3----q31.3 region are reviewed with emphasis on limb anomalies.

Asunto(s)

Deleción Cromosómica , Cromosomas Humanos Par 7 , Ectromelia/genética , Bandeo Cromosómico , Ectromelia/diagnóstico por imagen , Deformidades Congénitas de la Mano/genética , Humanos , Recién Nacido , Masculino , Radiografía

RESUMEN

In the terminus-generating (ter) reaction of phage lambda, the phage enzyme terminase catalyzes the production of staggered nicks within the cohesive-end nicking site (cosN). Although the two nicks are related by a rotational symmetry axis that bisects cosN, the in vitro ter reaction is strikingly asymmetric at the nucleotide level. Nicking of the lambda r strand precedes nicking of the I strand. Furthermore, when the two nicking reactions are uncoupled, they have different nucleotide cofactor requirements. ATP plays critical roles during cos cleavage: First, nicking of both DNA strands is stimulated by the addition of ATP. Second, ATP is required for the correct specificity of r-strand nicking since, in the absence of nucleotide, the r-strand nick is shifted 8 bases to the left. Studies with nonhydrolyzable analogs indicate that ATP hydrolysis is not required for these functions. However, after the two nicks are made, terminase catalyzes a disengagement of the cohered ends in a reaction that requires ATP hydrolysis.

Asunto(s)

Adenosina Trifosfato/metabolismo , Bacteriófago lambda/genética , ADN Viral/metabolismo , Endodesoxirribonucleasas/fisiología , Proteínas Virales/fisiología , Nucleótidos de Adenina/metabolismo , Secuencia de Bases , Cinética , Secuencias Reguladoras de Ácidos Nucleicos , Relación Estructura-Actividad

RESUMEN

The main features of Wiedemann-Beckwith syndrome (WBS) include macroglossia, abdominal wall defects, visceromegaly, gigantism, hypoglycemia, ear creases, nevus flammeus, and mid-face hypoplasia. Twenty-two cases of WBS were examined clinically and cytogenetically, and compared to 226 previously reported cases. Aspects of the clinical evaluations are discussed. All individuals examined were chromosomally normal with no evidence of 11p abnormality as has been reported recently. The relevance of a possible relationship between clinical findings, chromosome abnormalities, and genes present on 11p is discussed. Transmission of this condition is most consistent with autosomal dominant inheritance with incomplete penetrance.

Asunto(s)

Síndrome de Beckwith-Wiedemann/genética , Aberraciones Cromosómicas , Adolescente , Síndrome de Beckwith-Wiedemann/mortalidad , Peso al Nacer , Estatura , Peso Corporal , Niño , Preescolar , Cromosomas Humanos Par 11 , Femenino , Genes Dominantes , Humanos , Lactante , Recién Nacido , Masculino , Linaje , Factores Sexuales