STUDIES ON THE 5' REGULATORY REGION OF THE HUMAN CYTOCHROME C1 GENE

A fragment from the 5' nanking region (nt -557/+136) of the human cylo chrome cl gene was amplified by PCR. A subfragment (-557/+61) was prep ared and then cloned in front of the CAT reporter gene to form plasmid phCCl. When transfected into NIH3T3 cells, phCCl supported expression of CAT activity which was 40 fold greater than that driven from a pro moterless CAT-containing plasmid. In addition, CAT expression driven f rom the cytochrome cl -557/+61 fragment was nearly as high as that dri ven from the SV40 early promoter/enhancer. Thus, the -557/+61 region c ontains a highly efficient promoter/enhancer for the cytochrome cl gen e. We also provide evidence that thyroid hormone might induce a rat li ver nuclear factor which binds lo the -557/+61 region. This factor cou ld play a role in the thyroid hormone-induced increase (30 fold) in ra t liver cytochrome cl mRNA.