A WINGED-HELIX FAMILY MEMBER IS INVOLVED IN A STEROID HORMONE-TRIGGERED REGULATORY CIRCUIT

A common theme emerging in eukaryotic gene regulation is that maximal gene induction requires several transcription factors acting in concer t to regulate the activation of critical genes. Increasingly, nuclear receptors play key roles in orchestrating this regulation, often by in tegrating additional signaling pathways, through complex regulatory el ements known as hormone response units. The ovalbumin gene contains on e such unit, known as the steroid-dependent regulatory element. The bi nding of the chicken ovalbumin induced regulatory protein-I (Chirp-I) to this element occurs only in response to treatment with estrogen and glucocorticoid. Evidence presented herein demonstrates that Chirp-I h as many features in common with the winged-helix (W-H) family of trans cription factors. The binding sites for Chirp-I and for the W-H protei ns have similar sequence recognition requirements. Northern blots esta blish that members of the W-H family are expressed in oviduct. Most co nvincing, the Chirp-I complex interacts with two different antibodies specific to W-H family members. The culmination of this work supports the hypothesis that Chirp-I is a member of the W-H family, and it lend s credence to the idea that W-H proteins are essential components of s ome steroid hormone regulatory circuits.