Avian winged helix proteins CWH-1, CWH-2 and CWH-3 repress transcription from Qin binding sites

The chicken winged helix proteins, CWH-1, CWH-2 and CWH-3, were isolated and identified by homology cloning using the winged helix sequence of the retroviral oncogene qin as a probe. The CWH proteins act as growth stimulators in chicken embryo fibroblasts and in this activity resemble the Qin protein. Qin is a transcriptional regulator that functions as a repressor, and its oncogenic potential is correlated with the ability to repress transcription. In this communication we show that CWH proteins are localized in the cell nucleus, recognize the Qin DNA binding site and also function as transcriptional repressors. The repression activity of CWH-3 was mapped to the region of amino acids 211 to 311, a domain that is homologous to the major repression domain of Qin.