Endocrinology, Vol 137, 2910-2917, Copyright © 1996 by Endocrine Society

ARTICLES

Testosterone regulates tissue-specific changes in the binding of a 47- kilodalton protein to a highly conserved sequence in the 3' untranslated region of epidermal growth factor messenger ribonucleic acid

LG Sheflin, EM Brooks and SW Spaulding
The Research Service at the VA Western New York Healthcare System, Buffalo, New York 14215, USA.

Epidermal growth factor (EGF) transcripts that use the terminal polyadenylation signal display a dramatic sex difference in the pattern of polyadenylation in the murine submaxillary gland (SMG), whereas those in the kidney do not. It takes 3 days before testosterone treatment begins to change the polyadenylation pattern in female SMG to resemble the male pattern, a finding that supports previous suggestions that posttranscriptional mechanisms are involved in regulating EGF expression. The conservation of a unique 23-b sequence centered on the terminal polyadenylation signal in all published mammalian EGF sequences suggested that trans-acting factors involved in EGF messenger RNA (mRNA) metabolism might bind to this sequence. To investigate this, we prepared 32P-RNA containing the 3' terminal EGF 23-b sequence plus a short poly-A tail, and incubated it with SMG cytosol. Cytosol retarded the electrophoretic mobility of this RNA as a single prominent band on 8% PAGE, and by UV-cross-linking, a single prominent 47-kDa protein was detected on 10% SDS-PAGE. Trypsin abolished both the gel-retarding and cross-linking activities. Cytosol from female SMGs contained approximately 8 times more of both the RNA binding activities than male cytosol. Injecting testosterone (200 microg QOD) into female mice altered both the RNA binding activities in a biphasic fashion, initially increasing them by about 40% at 2 days, then decreasing them by about 65% > or = 5 days, reaching male levels. Kidney cytosol contained both RNA binding activities but displayed neither sexual dimorphism nor testosterone-responsiveness. The tissue-specific testosterone-dependent changes observed in the 47-kDa protein occur before the increase in EGF mRNA levels and before the change in EGF mRNA polyad-enylation, so this cytosolic protein could be a trans- acting factor involved in EGF polyadenylation.

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