Coordinate regulation of two estrogen-dependent genes in avian liver.

Abstract

Livers of egg-laying species contain abundant mRNA encoded by both estrogen-responsive and constitutively expressed genes [some of these genes code for egg yolk proteins]. The construction of c[complementary]DNA clones from 3 members of the abundant mRNA class of hen liver is reported. One of these mRNA species was identified as serum albumin mRNA, and another as vitellogenin mRNA. The 3rd member of the group was identified as apoVLDLII [apolipoproteins of very low density lipoprotein II)] mRNA. Hybridization analyses using cloned cDNA probes indicate that expression of the apoVLDLII gene in rooster liver, like that of the vitellogenin gene, is completely dependent on the administration of estrogen. The apoVLDLII and vitellogenin genes appear to be the only genes capable of high rates of expression in the liver that exhibit such an exceptional response to the hormone. Administration of estrogen resulted in the appearance of both mRNA species within 30 min, followed by a rapid accumulation to several thousand copies per cell. Removal of the hormone caused a marked destabilization of both vitellogenin mRNA and apoVLDLII mRNA. The absolute levels of serum albumin mRNA were unaffected by the hormone. Comparative studies on the structure and organization of these 3 genes may reveal elements involved in determining their rates of expression in the presence and absence of estrogen.