Abstract
A number of mutants of polyomavirus middle T antigen (MTag) were constructed into replication-competent avian retroviruses. To assess the ability of these MTag variants to transform and to associate with the avian p60c-src and p62c-yes proto-oncogene products, we used these viruses to infect chicken embryo fibroblasts. We found that the ability of individual mutant MTags to associate with p62c-yes correlated well with the ability of these mutants to transform, as has been previously shown for the association of MTag with p60c-src. All transformation-competent mutant MTags retained the ability to complex with p62c-yes. Two transformation-defective mutants, RX67 and RX68, which could weakly associate with p60c-src, were unable to associate with p62c-yes.dl1015, a transformation-defective mutant which could associate with p60c-src and with a phosphatidylinositol kinase activity, was also able to associate with p62c-yes. Therefore, some as yet unmeasured biochemical property is defective in this mutant.