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Mol. Cell. Biol., Sep 1995, 4672-4682, Vol 15, No. 9
A Subramanian, J Teixeira, J Wang and G Gil
Adult male rodents have a pulsatile profile of growth hormone (GH) release,
whereas female rodents have a relatively steady-state pattern with uniform,
albeit lower levels of GH. The expression of a number of sexually
differentiated hepatic proteins is primarily determined by these plasma GH
profiles and only secondarily regulated by gonadal hormones. An important
subset of these sexually dimorphic proteins is cytochrome P450s. CYP3A10/6
beta-hydroxylase is a cytochrome P450 that catalyzes the 6
beta-hydroxylation of lithocholic acid. CYP3A10/6 beta- hydroxylase is
expressed only in male hamsters; however, mimicking the male GH secretion
pattern in females induces expression of the gene to male levels. Using
chimeric CYP3A10/6 beta-hydroxylase promoter/luciferase reporter genes
transfected into hamster primary hepatocytes, we have shown a GH-mediated
induction of promoter activity. A combination of 5'-deletion constructs,
heterologous promoter constructs, and specific mutagenesis was used to
localize the DNA element involved in the GH-mediated regulation of
CYP3A10/6 beta- hydroxylase promoter activity, which resembles a STAT
binding site. Footprint and gel shift analyses confirmed that the
expression of the protein binding to this site is regulated by GH and that
the DNA- protein complex can be partially supershifted by anti-STAT-5
antibodies. This protein is 50% more abundant in male than in female
hamster livers, is absent in hypophysectomized female livers, and is
restored when hypophysectomized females are injected with GH in a manner
that masculinizes female hamsters in terms of CYP3A10/6 beta- hydroxylase
expression. The system characterized and described here is ideally suited
for dissecting the molecular details governing the sexually dimorphic
expression of liver-specific genes.
Copyright © 1995, American Society for Microbiology
A STAT factor mediates the sexually dimorphic regulation of hepatic cytochrome P450 3A10/lithocholic acid 6 beta-hydroxylase gene expression by growth hormone
Department of Biochemistry and Molecular Biology, University of Massachusetts Medical School, Worcester 01655, USA.
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