INTRACELLULAR ASSOCIATION OF THE PROTEIN PRODUCT OF THE ONCOGENE WITHTHE TATA-BINDING PROTEIN

The c-myc proto-oncogene encodes nuclear phosphoproteins that bind DNA in a sequence-specific fashion and appear to function as transcriptio nal activators. Here we demonstrate that a 40-kDa nuclear protein coim munoprecipitated with c-Myc specifically when nuclear proteins, extrac ted from nuclei of exponentially growing murine B-lymphoma WEHI 231 ce lls by using procedures for preparation of trans-acting factors, were reacted with anti-c-Myc antibodies made against different regions of t he c-Myc protein. In contrast, preparation of nuclear lysates under de naturing conditions significantly reduced this coprecipitation. Upon i ncubation of WEHI 231 cells with the reversible chemical cross-linking agent dithiobis(succinimidyl propionate), the 40-kDa protein could be cross-linked to c-Myc protein intracellularly. Identification of the 40-kDa protein as the TATA-binding protein (TBP) of the TFIID transcri ption initiation complex was made by comigration and V-8 protease mapp ing, which yielding identical peptide fragments upon digestion of the 40-kDa protein and material immunoprecipitated with an anti-TBP specif ic antibody. Furthermore, in vitro-translated TBP bound to the amino-t erminal portion of c-Myc. Column chromatography of cross-linked nuclea r proteins showed TBP to be in a large-molecular-weight complex with c -Myc, consistent with a transcription initiation complex. These result s indicate that intracellularly, c-Myc interacts with TBP, suggesting a mechanism of interaction of this oncoprotein with the basal transcri ption machinery.