INTERACTION OF A NOVEL SEX-DEPENDENT, GROWTH HORMONE-REGULATED LIVER NUCLEAR FACTOR WITH CYP2C12 PROMOTER

CYP2C12 is a steroid hydroxylase cytochrome P450 whose female specific expression in adult rat liver is transcriptionally activated by the c ontinuous plasma growth hormone (GH) profile characteristic of adult f e male rats, DNase I footprinting and gel mobility shift analysis of t he 5'-flank of the CYP2C12 gene were carried out to identify cis-actin g elements and trans-acting factors that may contribute to the GH-regu lated, sex-dependent transcription of this P450 gene, DNase I footprin ting analysis revealed sex- and GH-regulated DNase I hypersensitivity sites at the boundaries of several protein binding sites detected alon g a 1560-nucleotide upstream segment of CYP2C12, Five distinct sites b ound a novel continuous GH-regulated nuclear factor, GHNF, which is en riched in adult female and continuous GH-treated male liver nuclear ex tracts compared to untreated male liver nuclear extracts, Two other fo ot-printed sites correspond to binding sites for the liver transcripti on factors C/EBP and albumin D element-binding protein and a third to an HNF1 binding site. A specific binding site for GHNF was also found in the 5'-proximal promoter of CYP2C11, an adult male-specific liver P 450 gene, suggesting that GHNF may contribute to the doum-regulation o f that gene by continuous GH, GHNF was distinguished from the nuclear factors that bind to a GH response element upstream of the rat Spi 2.1 gene and is also distinct from the GH-activatable latent cytoplasmic transcription factors STAT 1, STAT 3, and STAT 5. These findings suppo rt the hypothesis that continuous GH-activated transcription of CYP2C1 2 in adult female rat liver (a) involves the activation of a novel GH- regulated nuclear factor which binds to multiple sites along the 5'-fl ank of this cytochrome P450 gene, and (b) proceeds via a signaling pat hway distinct from the GH pulse-activated STAT5 pathway proposed to in duce CYP2C11 and other male-expressed liver genes.