COMPARISON OF THE 5'-END OF THE RAT AND MOUSE CYSTATHIONINE BETA-SYNTHASE GENES

We have isolated and characterized a genomic fragment encompassing the first six exons and 2.6 kbp 5' flanking sequence of the rat cystathio nine beta-synthase (CBS) gene. A previously unknown exon approximately 3 kbp upstream of exon 1 was identified. The transcription start site was mapped to approximately 3 kbp upstream from the translation start codon and contains a consensus cap signal. The putative promoter regi on contains three GC boxes, in both orientations, and no TATA box. We have also compared a 1171-bp-long DNA sequence of the 5' end of the ra t CBS gene with the homologous mouse region of 1125 bp. We found two h omologous Spl sites in the mouse gene and an overall sequence conserva tion of 70% with 88-89% similarity in the 80-bp regions surrounding th e intron 0 splice sites.