DNA-binding activity is associated with purified myb proteins from AMV and E26 viruses and is temperature-sensitive for E26 ts mutants.

Oncogene protein products from avian myeloblastosis virus, p48v-myb, and from avian leukemia virus E26, p135gag-myb-ets, are located predominantly in the nucleus of nonproducer bone marrow cell clones, as revealed by indirect immunofluorescence. Both oncogene proteins were purified by immunoaffinity chromatography using monoclonal antibodies against p19 and immunoglobulins specific for myb, which was expressed in bacteria for antibody production. The purified proteins bind to DNA in vitro. In contrast, purified p135gag-myb-ets proteins from several mutants of E26 virus, temperature-sensitive for myeloblast transformation, either lost their abilities to bind to DNA or exhibited highly thermolabile DNA-protein interactions in vitro. DNA binding of AMV and E26 oncogene proteins is inhibited by myb-specific immunoglobulins. Our results suggest that lesions in the myb oncogene affect transformation as well as DNA binding of myb proteins in vitro.