TRANSCRIPTIONAL REGULATION OF SERTOLI-CELL IMMEDIATE-EARLY GENES BY INTERLEUKIN-6 AND INTERFERON-GAMMA IS MEDIATED THROUGH PHOSPHORYLATION OF STAT-3 AND STAT-1 PROTEINS

The immediate early genes are regulated by a variety of extracellular signals, including pleiotropic cytokines. The effects of the testicula r cytokines, interleukin-6 (IL-6) and interferon-gamma (IFN-gamma), on signal transducers and activators of transcription 3 and 1 (STAT-3 an d STAT-1) and on c-fos gene expression in primary Sertoli cells are su ggestive of their roles in differential function. Using the tyrosine p hosphorylation inhibitor, genistein, and electrophoretic mobility shif t assay, we show that IL-G and IFN-gamma induce nuclear factor STAT-3 and STAT-1 DNA-binding activity to the sis-inducible element of c-fos in a genistein-dependent pathway. Quantitative solution hybridization, Northern blot, and nuclear run-on analysis show that differential ind uction of c-fos, junB. and c-myc messenger RNA (mRNA) by these cytokin es occur at transcriptional levels. IL-6 stimulates c-fos mRNA levels by B-fold while increasing junB levels by 2-fold. IFN-gamma increases c-fos message 2-fold, but has no effect on junB mRNA levels. Furthermo re, genistein treatment blocks the induction of c-fos and junB gene ex pression, demonstrating that tyrosine phosphorylation of STAT proteins is involved in the cytokine regulation of the Sertoli immediate early genes. H7, a serine threonine phosphorylation inhibitor, also blocks c-ibs gene induction by IL-6 and IFN-gamma, but does not affect the DN A-binding activities of STAT-3 and STAT-1. Finally, IL-6 treatment of Sertoli cells (3-6 hr increases the amounts of activating protein-1 bi nding to activating protein-1 element and c-myc transcription.