INTERACTION OF ERYTHROPOIETIN RNA-BINDING PROTEIN WITH ERYTHROPOIETINRNA REQUIRES AN ASSOCIATION WITH HEAT-SHOCK-PROTEIN-70

Synthesis of erythropoietin (Epo), the glycoprotein hormone that regul ates red blood cell formation, is induced in response to low oxygen st ress (hypoxia), and is regulated at both transcriptional and post-tran scriptional levels. We have previously described an Epo RNA binding pr otein (ERBP) which specifically binds to the 3'-untranslated region of Epo mRNA and is likely involved in the regulation of Epo mRNA stabili ty. Since heat shock proteins (hsps) are induced in response to a vari ety of stresses, including hypoxia, we tested the possibility that hsp s are involved in ERBP-Epo RNA complex formation. When human anti-hsp7 0 antibody was added to ERBP-containing human hepatoma cell (Hep3B) ly sates, the ERBP-Epo RNA complex was inhibited in an electrophoretic mo bility band shift assay. In addition, the anti-hsp70 antibody-inhibite d complex could be rescued if lysates were pretreated with purified in ducible hsp70, but not with bovine serum albumin (BSA). In vivo studie s using quercetin to inhibit hsp70 induction support the notion that h sp70 is involved in ERBP-Epo RNA complex formation. Taken together, th ese findings suggest involvement of hsp70 in ERBP-Epo mRNA complex for mation, and our model suggests a novel role for hsps in the regulation of EPO mRNA stability.