Nonselective expression of simian virus 40 large tumor antigen fragments in mouse cells

To understand the role of various functional domains of simian virus 40 early tumor antigens, we have cloned and introduced into mouse cells portions of early simian virus 40 DNA. Two types of truncated large tumor antigen (33 and 12.3 kilodaltons), as well as small tumor antigen, were identified by immunoprecipitation. Both truncated large tumor antigens have been found to be overproduced with respect to the small tumor antigen, although the 12.3-kilodalton truncated large tumor antigen was more stable than the 33-kilodalton one. Nonviral 53-kilodalton protein was not found associated with either truncated large tumor antigen in immunoprecipitations.