Polyoma virus mutants lacking one or both tyrosines at position 315 and 322 of wildtype middle T antigen have been constructed. The effects of the removal of these tyrosines are additive for middle T phosphorylation in immune complexes, with tyrosine 315 being the major acceptor site and 322 a secondary site. Previous studies have shown little or no effect of deletion of tyrosine 322 on transforming ability, whereas a strong effect has been seen by substitution of phenylalanine for tyrosine 315. In contrast to the phosphokinase results, there is no additive effect of combining these mutations on the viruses' transforming ability. Thus the double mutant lacking both tyrosines has the same weak transforming activity as the single mutant containing tyrosine 322 and phenylalanine 315. Phosphorylation of middle T antigen at tyrosine 322 by pp60c-src or other tyrosine-specific cellular protein kinase is therefore unimportant for transformation.
ASJC Scopus subject areas
- Infectious Diseases