RESUMO
In order to contribute to the development of the transcriptional map of chromosome 21, we performed exon trapping using cosmid clones mapped in the region 21q22.1-22.2 and identified a number of potential exons. One of the trapped exons (Genbank No. AF026200) showed a strong homology with the mouse Bach1 gene (Genbank No. D86603), a transcription factor regulating gene expression. We then isolated the full-length coding region of the human BACH1 gene using expressed sequence tags, reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends. The predicted BACH1 protein contains 736 amino acids and is 88% identical to its mouse homolog. It contains basic leucine zipper and BTB-zinc finger domains (which are directly involved in DNA binding for transcription regulation). The BACH1 gene maps in a relatively gene-poor region on 21q22.1 in yeast artificial chromosome 814c1 of the collection of Chumakov et al. Northern blot analysis revealed that it is expressed as an mRNA species of approximately 5.8 kb in all 16 adult and 4 fetal tissues examined; an additional mRNA species of 2.8 kb was observed in adult testis. The contribution of the BACH1 gene to the pathophysiology of trisomy or monosomy 21 is unknown. In addition, no monogenic disorders associated with mutations in the BACH1 gene have yet been identified.
Assuntos
Mapeamento Cromossômico , Cromossomos Humanos Par 21/genética , Genes Reguladores/genética , Fatores de Transcrição/genética , Adulto , Sequência de Aminoácidos , Sequência de Bases , Fatores de Transcrição de Zíper de Leucina Básica , Clonagem Molecular , Síndrome de Down/genética , Éxons/genética , Proteínas de Grupos de Complementação da Anemia de Fanconi , Regulação da Expressão Gênica/fisiologia , Humanos , Dados de Sequência Molecular , Especificidade de Órgãos , RNA Mensageiro/análise , Análise de Sequência de DNARESUMO
Exon trapping was used to clone portions of genes from the Down syndrome critical region (DSCR) of human chromosome 21. One trapped sequence showed complete homology with nucleotide sequence U20980 (GenBank), which corresponds to the gene for the p60 subunit of the human chromatin assembly factor-1 (CAF1A). We mapped this gene to human chromosome 21 by fluorescence in situ hybridization, by the use of somatic cell hybrids, and by hybridization to chromosome 21-specific YACs and cosmids. The CAF1A gene localizes to YACs 745H11 and 230E8 of the Chumakov et al. (1992, Nature 359: 380) YAC contig, within the DSCR on 21q22. This CAF1A, which belongs to the WD-motif family of genes and interacts with other polypeptide subunits to promote assembly of histones to replicating DNA, may contribute in a gene dosage-dependent manner to the phenotype of Down syndrome.
Assuntos
Proteínas Cromossômicas não Histona , Cromossomos Humanos Par 21 , Proteínas de Ligação a DNA/genética , Síndrome de Down/genética , Animais , Sequência de Bases , Linhagem Celular , Fator 1 de Modelagem da Cromatina , Mapeamento Cromossômico , Cromossomos Artificiais de Levedura , Primers do DNA , Humanos , Células Híbridas , Hibridização in Situ Fluorescente , Camundongos , Dados de Sequência Molecular , Reação em Cadeia da PolimeraseRESUMO
Exon trapping/amplification was used to clone portions of genes from the Down syndrome critical region (DSCR) of human chromosome 21q22. Two trapped sequences showed complete homology with nucleotide sequence D23672 of Genbank which corresponds to the gene for the human holocarboxylase synthetase (HCS) that was previously assigned to chromosome 21. We precisely mapped this gene to the DSCR by somatic cell hybrids, chromosome 21-specific YACs, and hybridization to chromosome 21-specific cosmids; it localizes to YACs 745H11 and 230E8 of the Chumakov et al. (Nature 359:380, 1992) YAC contig in a region of less that one megabase between markers D21S333 and D21S267. This HCS gene may contribute in a gene dosage-dependent manner to the phenotype of Down syndrome.
