Transcriptional regulation of the cyclin D1 promoter by STAT5: its involvement in cytokine-dependent growth of hematopoietic cells

STAT5 is a member of a family of transcription factors that participate in the signal transduction pathways of many hormones and cytokines, Although S TAT5 is suggested to play a crucial role in the biological effects of cytok ines, its downstream target(s) associated with cell growth control is large ly unknown. In a human interleukin-3 (IL-3)-dependent cell line F-36P-mpl, the induced expression of dominant-negative (dn)-STAT5 and of dn-ras led to inhibition of IL-3-dependent cell growth, accompanying the reduced express ion of cyclin D1 mRNA. Also, both constitutively active forms of STAT5A (1* 6-STAT5A) and ras (H-ras(G12V)) enabled F-36P-mpl cells to proliferate with out added growth factors. In NIH 3T3 cells, 1*6-STAT5A and N-ras(G12V) indi vidually and cooperatively transactivated the cyclin D1 promoter in lucifer ase assays. Both dn-STAT5 and dn-ras suppressed IL-3-induced cyclin D1 prom oter activities in F-36P-mpl cells, Using a series of mutant cyclin DI prom oters, 1*6-STAT5A was found to transactivate the cyclin D1 promoter through the potential STAT-binding sequence at -481 bp, In electrophoretic mobilit y shift assays, STAT5 bound to the element in response to IL-3, Furthermore , the inhibitory effect of dn-STAT5 on IL-3-dependent growth was restored b y expression of cyclin DI, Thus STAT5, in addition to ras signaling, appear s to mediate transcriptional regulation of cyclin D1, thereby contributing to cytokine-dependent growth of hematopoietic cells.