Deletion mapping of a short polyoma virus middle T antigen segment important for transformation

Viable polyoma virus mutants were constructed that had small deletions in the early region of the genome. The deletions together removed most of the segment missing from the genome of the nontransforming mutant dl23 (N. Smolar and B. E. Griffin, J. Virol. 38:958-967, 1981). The transformation properties, as measured by colony formation in soft agar, of mutants with overlapping or contiguous deletions showed that part or all of the middle T antigen segment, consisting of the short amino acid sequence Glu4-Tyr-Met-Pro-Met, was essential for the activity of the protein in transformation. However, the segment could be deleted without significant effect on the in vitro protein kinase activity associated with the middle T antigen.