Androgens regulate the binding of endogenous HuR to the AU-rich 3'UTRs of HIF-1alpha and EGF mRNA.

The 3'UTRs of mammalian HIF-1alpha and EGF mRNA contain several highly conserved AU-rich elements (ARE) known to control the turnover of labile mRNAs by binding ARE-binding proteins that regulate nucleocytoplasmic shuttling, translation, and degradation. Androgens regulate the level and subcellular shuttling of HuR, a major ARE-binding protein that stabilizes many ARE-mRNAs. Pull down of biotinylated 3'UTRs of HIF-1alpha or EGF enriches HuR on blots from Jurkat cell lysates 5-fold, and enriches the amount of RNase-protected biotinylated RNA that comigrates with HuR approximately 10-fold. Dihydrotestosterone treatment decreases the HuR-protected riboprobe pulled down from total Jurkat cell lysates by 30-40%, apparently reflecting shifts in HuR from the nucleus to the cytoplasm. Androgen treatment also changes the amount of HuR-protected riboprobe pulled down from a PC-3 clone expressing a functional androgen receptor. The shift in the amount of riboprobe bound by HuR suggests that androgen is up-regulating endogenous ARE-mRNAs that can compete for binding endogenous HuR. These changes in the shuttling and ARE-binding of endogenous HuR indicate that androgen can act posttranscriptionally to regulate ARE-mRNAs, including HIF-1alpha and EGF.