GROWTH-HORMONE INDUCTION OF HEPATIC SERINE-PROTEASE INHIBITOR-2.1 TRANSCRIPTION IS MEDIATED BY A STAT5-RELATED FACTOR-BINDING SYNERGISTICALLY TO 2 GAMMA-ACTIVATED SITES

A growth hormone (GH)-inducible nuclear factor (GHINF) from rat liver has been purified to near homogeneity. On SDS-polyacrylamide gel elect rophoresis and UV-cross-linking, a major band of mass similar to 93 kD a and a minor band of similar to 70 kDa are detected in the purified f raction. DNase I footprinting using purified GHINF yields a protected region of -149/-115 on the rat serine protease inhibitor 2.1 (Spi 2.1) promoter encompassed within the growth hormone response element (GHRE ). Mutational analysis demonstrated that GHINF binds synergistically t o two gamma-interferon activated sites (GAS) within the GHRE, with the 3' element being the pivotal binding domain. Functional assays show t hat both GAS elements are necessary for full GH response. GHINF has no immunoreactivity with either a C-terminal Stat1 antibody or an N-term inal Stat3 antibody, while cross-reacting with a C-terminal Stat5 mono clonal antibody. GHINF will bind to two GAS elements from the Stat5 bi nding region of the beta-casein gene. These studies indicate that GHIN F is a Stat5-related factor binding synergistically to two GAS element s to activate Spi 2.1 transcription.