ISOLATION OF THE HUMAN BACH1 TRANSCRIPTION REGULATOR GENE, WHICH MAPSTO CHROMOSOME 21Q22.1

In order to contribute to the development of the transcriptional map o f 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 homo logy with the mouse Bach1 gene (Genbank No. D86603), a transcription f actor regulating gene expression. We then isolated the full-length cod ing region of the human BACH1 gene using expressed sequence tags, reve rse transcription-polymerase chain reaction and rapid amplification of cDNA ends. The predicted BACH1 protein contains 736 amino acids and i s 88% identical to its mouse homolog. It contains basic leucine zipper and BTB-zinc finger domains (which are directly involved in DNA bindi ng for transcription regulation). The BACH1 gene maps in a relatively gene-poor region on 21q22.1 in yeast artificial chromosome 814cl of th e collection of Chumakov et al. Northern blot analysis revealed that i t is expressed as an mRNA species of approximately 5.8 kb in all 16 ad ult 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 t he pathophysiology of trisomy or monosomy 21 is unknown, In addition, no monogenic disorders associated with mutations in the BACH1 gene hav e yet been identified.