The isolation and characterization of the human cytochrome b5 gene

From a series of lambda and cosmid libraries, we isolated DNA sequences corresponding to the complete coding region for the human cytochrome b5 (CYB5) gene. The overall gene organization was the same as the bovine and rabbit CYB5 genes. One cosmid clone containing exon I plus the 5' flanking region was extensively characterized. From this clone we obtained 2000 bp of 5' flanking sequence, containing several distinctive GC rich regions, potential trans-acting factor binding sites and a 74 bp direct repeat. A series of deletion constructs were made in the pGL2 luciferase vector and then used to transfect HepG2 and K562 cells. The data obtained suggest the presence of two promotors and one silencer region in the analyzed 5' sequence.