The C-terminal region of cellular Qin oligomerizes: correlation with oncogenic transformation and transcriptional repression.

Expression of the oncoprotein Qin induces tumors in chickens and oncogenic transformation of chicken embryo fibroblasts in culture. We performed a detailed deletion analysis of the C-terminal region of Qin (amino acids 246-451, extending from the winged helix domain to the C-terminus) and identified amino acids 246-379 as important for transformation. The same region mediates homo-oligomerization of Qin as documented in vitro by GST pulldowns and in vivo by coimmunoprecipitation.

Binding of the corepressor TLE1 to Qin enhances Qin-mediated transformation of chicken embryo fibroblasts.

The oncoprotein Qin is a member of the winged helix family of transcriptional regulators. The region C-terminal to its winged helix DNA-binding domain is required for transformation of chicken embryo fibroblasts. We isolated the corepressor TLE1 as a binding partner for Qin in a yeast two-hybrid screen and localized the TLE1-binding region to a 60 amino-acid stretch directly C-terminal of the winged helix domain of Qin.