Middle-T antigen (middle-T), the transforming gene product of polyomavirus, associates with several cellular tyrosine kinases, such as pp60(c-src). Complex formation leads to kinase activation and is essential for cell transformation. Middle-T-associated as well as uncomplexed pp60(c-src) is predominantly found in the plasma membrane. We transfected mouse 3T3 fibroblasts with a mutated c-src gene (2Ac-src), allowing the expression of a protein containing alanine instead of glycine in position 2 of the primary translation product. Contrary to the wild-type c-src gene product, pp60(c-src(2A)) was not myristylated and accumulated in the cytoplasm instead of being transferred to cellular membranes. The mutant protein was able to associate with middle-T and was activated similarly to the wild-type c-src gene product. Both wild-type and 2A mutant protein were membrane associated upon complex formation with middle-T. This finding suggests that the putative carboxy-terminal membrane anchor sequence of middle-T is sufficient to hold middle-T-associated pp60(c-src(2A)) in the plasma membrane.
ASJC Scopus subject areas
- Insect Science