Interactions between Tat and TAR and human immunodeficiency virus replication are facilitated by human cyclin T1 but not cyclins T2a or T2b.
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The transcriptional transactivator (Tat) from the human immunodeficiency virus (HIV) does not function efficiently in Chinese hamster ovary (CHO) cells. Only somatic cell hybrids between CHO and human cells and CHO cells containing human chromosome 12 (CHO12) support high levels of Tat transactivation. This restriction was mapped to interactions between Tat and TAR. Recently, human cyclin T1 was found to increase the binding of Tat to TAR and levels of Tat transactivation in rodent cells. By combining individually with CDK9, cyclin T1 or related cyclins T2a and T2b form distinct positive transcription elongation factor b (P-TEFb) complexes. In this report, we found that of these three cyclins, only cyclin T1 is encoded on human chromosome 12 and is responsible for its effects in CHO cells. Moreover, only human cyclin T1, not mouse cyclin T1 or human cyclins T2a or T2b, supported interactions between Tat and TAR in vitro. Finally, after introducing appropriate receptors and human cyclin T1 into CHO cells, they became permissive for infection by and replication of HIV. (+info)
Analysis of spinocerebellar ataxia type 2 gene and haplotype analysis: (CCG)1-2 polymorphism and contribution to founder effect.
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Spinocerebellar ataxia type 2 is a familial spinocerebellar ataxia with autosomal dominant inheritance. The gene responsible was recently cloned and this disorder was found to be the result of a CAG expansion in its open reading frame. We analysed 13 SCA2 patients in seven unrelated families in Gunma Prefecture, Japan. In four of the seven families, we detected CCG or CCGCCG interruptions in only the expanded alleles. Cosegregation of these polymorphisms with SCA2 patients was established within each family. Together with the results of haplotype analyses, we considered that at least two founders were present in our area and that these (CCG)1-2 polymorphisms may make analysis of founder effects easier. By sequencing analysis we found that although the number of the long CAG repeat varied in each subclone of expanded alleles, these polymorphisms did not change their configuration. This finding suggests that CCG or CCGCCG sequences are stable when surrounded by the long CAG repeat and a single CAG. Moreover, the presence of these polymorphisms may lead to miscounting the repeat size by conventional estimation using a size marker such as an M13 sequencing ladder. Therefore we should consider these polymorphisms and accurately determine the repeat size by sequencing. (+info)
Unique forms of human and mouse nuclear receptor corepressor SMRT.
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Nuclear hormone receptors have been shown to repress transcription in the absence of ligand. This repression is mediated by a corepressor complex that contains the Sin3A protein and histone deacetylases (HDAC1 and 2). Studies by several groups demonstrate that this complex is recruited to nuclear receptors through the highly related corepressors SMRT (silencing mediator of retinoid acid and thyroid hormone receptor) and N-CoR (nuclear receptor corepressor). We describe here the cloning, characterization, and chromosomal mapping of forms of human and mouse SMRT that includes a 1,000-aa extension, which reveals striking homology to the amino terminus of N-CoR. Structure and function studies of wild-type and natural splicing variants suggest the presence of 3-4 amino terminal domains that repress in a cooperative as well as mechanistically distinct fashion. (+info)
Structure and chromosomal assignment of the human lectin-like oxidized low-density-lipoprotein receptor-1 (LOX-1) gene.
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We have reported the cDNA cloning of a modified low-density-lipoprotein (LDL) receptor, designated lectin-like oxidized LDL receptor-1 (LOX-1), which is postulated to be involved in endothelial dysfunction and the pathogenesis of atherosclerosis. Here, we determined the organization of the human LOX-1 gene, including the 5'-regulatory region. The 5'-regulatory region contained several potential cis-regulatory elements, such as GATA-2 binding element, c-ets-1 binding element, 12-O-tetradecanoylphorbol 13-acetate-responsive element and shear-stress-responsive elements, which may mediate the endothelium-specific and inducible expression of LOX-1. The major transcription-initiation site was found to be located 29 nucleotides downstream of the TATA box and 61 nucleotides upstream from the translation-initiation codon. The minor initiation site was found to be 5 bp downstream from the major site. Most of the promoter activity of the LOX-1 gene was ascribed to the region (-150 to -90) containing the GC and CAAT boxes. The coding sequence was divided into 6 exons by 5 introns. The first 3 exons corresponded to the different functional domains of the protein (cytoplasmic, transmembrane and neck domains), and the residual 3 exons encoded the carbohydrate-recognition domain similar to the case of other C-type lectin genes. The LOX-1 gene was a single-copy gene and assigned to the p12.3-p13.2 region of chromosome 12. Since the locus for a familial hypertension has been mapped to the overlapping region, LOX-1 might be the gene responsible for the hypertension. (+info)
Evaluation of trisomy 12 by fluorescence in situ hybridization in peripheral blood, bone marrow and lymph nodes of patients with B-cell chronic lymphocytic leukemia.
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BACKGROUND AND OBJECTIVE: Trisomy 12 is the most common numerical chromosomal aberration in patients with B-cell chronic lymphocytic leukemia (B-CLL). Fluorescence in situ hybridization (FISH) has improved the detection of this cytogenetic abnormality and has made detection possible in all phases of the cell cycle. The presence of the trisomy 12 positive (+12) cell population has generally been investigated in leukemic cells obtained from the peripheral blood of CLL patients. To ascertain whether trisomy 12 is expressed homogeneously in cells of different hemopoietic tissues, we applied FISH to lymph node, peripheral blood and bone marrow samples obtained simultaneously from 23 untreated B-CLL patients. DESIGN AND METHODS: Twenty-three newly diagnosed patients with B-CLL, 15 in stage B and 8 in stage C, were included in the present study. Peripheral blood smears, bone marrow aspirate smears and lymph node touch imprints were collected from each patient at diagnosis. Cytologic preparations were examined by light microscopy in order to assess the lymphocyte morphology. Immunophenotyping was performed by cytofluorimetric analysis of the peripheral blood, bone marrow and lymph node mononuclear cell suspensions. The diagnosis was supported in all cases by histologic findings in bone marrow biopsy and lymph node biopsy specimens. Fluorescence in situ hybridization was performed on smears of blood and aspirated bone-marrow and lymph node touch imprints obtained by fresh tissue apposition. RESULTS: In 6 of the 23 cases (26%) trisomy 12 was clearly present in all tissues examined. A comparative analysis of the three different hemopoietic tissues was performed. A higher percentage of leukemic CD5+CD23+ cells was detected in lymph nodes than in peripheral blood and bone marrow. A significantly higher proportion of trisomic cells was observed in lymph nodes samples than in peripheral blood or bone marrow smears of trisomy 12 positive CLL patients. INTERPRETATION AND CONCLUSIONS: Several previous reports show that only a proportion of malignant B-CLL cells carry trisomy 12 when analyzed by interphase FISH. The higher proportion of +12 cells in lymph nodes than in peripheral blood or bone marrow of CLL patients with trisomy 12 could reflect different cell distributions in different tissues, or lymph node specific tropism, or proliferative advantage in selected tissue. At present, the role of trisomy 12 in the pathogenesis of lymphoproliferative disorders is unclear. (+info)
Association and linkage analysis of candidate chromosomal regions in multiple sclerosis: indication of disease genes in 12q23 and 7ptr-15.
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Four recent genome-wide screen studies in multiple sclerosis (MS) identified a number of candidate regions for susceptibility genes in addition to the HLA complex in 6p21. However, none of these regions provided formally significant evidence for genome-wide linkage. We have investigated such regions in 46 Swedish multiplex MS families, 28 singleton families, 190 sporadic MS patients and 148 normal controls by parametric and nonparametric linkage and association analysis. One microsatellite marker, in 12q23, provided evidence for association in addition to suggestive transmission distortion and slightly positive linkage. In addition, a marker in 7ptr-15 showed a significant transmission distortion as well as a highly significant score in affected pedigree member analysis, but not quite significant deviations in association analysis. One of three markers in 5p, a region implicated in all four previous studies, showed a weakly positive lod score, but no other evidence of importance. Markers in 2p23, 5q11-13, 6q25, 7q21-22, 11q21-23, 13q33-34, 16p13.2, 18p11.32-23, Xp21.3 provided little or no evidence of importance for MS. In summary, these data support the importance of genome-wide screens in the identification of new candidate loci in polygenic disorders. (+info)
Structural organization and splice variants of the POLE1 gene encoding the catalytic subunit of human DNA polymerase epsilon.
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The catalytic subunit of human DNA polymerase epsilon, an enzyme involved in nuclear DNA replication and repair, is encoded by the POLE1 gene. This gene is composed of 51 exons spanning at least 97 kb of genomic DNA. It was found to encode three alternative mRNA splice variants that differ in their 5'-terminal sequences and in the N-termini of the predicted proteins. A CpG island covers the promoter region for the major transcript in HeLa cells. This promoter is TATA-less and contains several putative binding sites for transcription factors typical of S-phase-up-regulated and serum-responsive promoters. Potential promoter regions were also identified for the two other alternative transcripts. Interestingly, no nuclear polyadenylation signal sequence was detected in the 3'-untranslated region, although a poly(A) tail was present. These results suggest a complicated regulatory machinery for the expression of the human POLE1 gene, including three alternative transcripts expressed from three promoters. (+info)
Pathogenesis of testicular germ cell tumours.
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Human germ cell tumours comprise a heterogeneous group of neoplasms. In the testis, three entities are distinguished, the teratomas-yolk sac tumours of the infantile testis, the seminomas and nonseminomas of adolescents and adults, and the spermatocytic seminomas. Studies on epidemiology, histology, clinical behaviour, and chromosomal constitution of these tumours support the concept of distinct entities derived from germ cells but each with a different pathogenesis. Either the teratomas of the infantile testis show no chromosomal aberrations, or display a pattern of over- and under-representation of (parts of) chromosomes as detected in the yolk sac tumours of the infantile testis. In contrast, the seminomas and nonseminomas reveal a consistent pattern of losses and gains, that is, chromosomes 11, 13 and 18, and 7, 8 and X, respectively, that is different from that found in the infantile testis teratomas and yolk sac tumours. The most consistent structural chromosomal abnormality is an isochromosome 12p. Tumours lacking i(12p) have other structural abnormalities of 12p, among them amplification of 12p11.2-p12.1. The pathogenetically relevant genes on 12p11.2-p12.1 are probably on a fragment of about 1.7 mb. Gain of 12p sequences may be related to invasive growth. Gain of chromosome 9 is the only consistent chromosomal anomaly of spermatocytic seminomas. Infantile teratomas and spermatocytic seminomas are benign tumours. Infantile yolk sac tumour is a malignant germ cell tumour. Seminomas and nonseminomas are malignant, and the most common cancer in young Caucasian males. The cure rate of seminomas and non-seminomas with radio- and chemotherapy is over 90%, which is higher than that of any other solid cancer in adults. In addition, the precursor lesions of these tumours can be treated readily, justifying efforts to develop means for early diagnosis. Finally, the pathogenetic relationship between seminomas and nonseminomas, and the available animal models for the three groups of testicular germ cell tumours are discussed. (+info)