Gene regulation and developmental roles of winged helix transcription factors in the chick oviduct

Steroid hormones have been implicated in several physiological processes, including regulation of gene transcription, mRNA stabilization, and differentiation and development. The chick oviduct represents an excellent system in which to study many of these hormonal effects. Within the magnum portion of the chick oviduct, the ovalbumin gene is transcriptionally regulated by estrogen and glucocorticoids in a secondary response manner. Previous binding and functional data identified a protein binding site, the Chirp-I (Chicken oviduct Induced Regulatory Protein - I) site, located in the Steroid Dependent Regulatory Element (SDRE) of the ovalbumin 5' regulatory region. The Chirp-I site is required for steroid induction and is similar to the consensus site for the winged helix (W-H) family of transcription factors. Data presented herein demonstrates that W-H family members are expressed in the chicken oviduct, and that the Chirp-I site is capable of binding purified and in vitro expressed W-H proteins. In addition, the protein(s) that binds the Chirp-I site from oviduct nuclear protein extracts is competed by antibodies directed at W-H family members. Taken together, these data suggest that Chirp-I is a W-H family member. In light of this, the chick homolog of the W-H family member HNF-3beta was cloned from an oviduct cDNA library. However, analysis of chick HNF-3beta (cHNF-3beta) binding properties suggest that cHNF-3beta is not Chirp-I. Further characterization of cHNF-3beta demonstrated that it is expressed in several adult tissues, with each tissue type expressing a different length mRNA transcript. Moreover, estrogen stabilizes cHNF-3beta mRNA in oviduct, liver, and possibly kidney, but down regulates cHNF- 3beta mRNA levels in lung. Finally, cHNF-3beta expression patterns correlate with it being involved in oviduct differentiation and development, since cHNF-3beta mRNA levels are induced within 12 hours of stimulating the cells of the oviduct to differentiate. In conclusion, this work demonstrates that winged helix transcription factors play both gene regulatory and developmental roles in the chick oviduct.