REGULATION OF JUN EXPRESSION AND ACTIVATION OF AP-1 ACTIVITY BY ERYTHROPOIETIN

Erythropoietin (EPO) is a molecule which regulates hemoglobin gene exp ression during erythroid proliferation and differentiation. However, t he mechanism by which it regulates gene expression is poorly understoo d. Secondly, unlike other hematopoietic factors which induce expressio n of early response genes, it is unknown whether EPO is capable of ind ucing the expression and activation of early response genes. In this s tudy, evidence is presented that EPO induces the expression of early r esponse genes c-jun, junD and c-fos mRNA, stimulates jun protein synth esis and induces activation of 5 x AP-1/CAT activity in human erythrol eukemia K562 cells. Also, EPO appears to regulate jun expression at tr anscriptional, post transcriptional and translational levels. These ob servations suggest that jun and fos expression may be relevant in the mechanism of growth control by EPO. (C) 1996 Academic Press, Inc.