A rat mutant cell clone showing temperature-dependent transformed phenotypes with functional expression of the src gene product.

The cellular mutant B814 isolated from a Fischer rat cell line shows temperature-sensitivity of focus formation on infection with Moloney murine sarcoma virus (Mo-MSV) and Rous sarcoma virus (RSV). An RSV-transformed clone (S814-2) isolated from B814 cells shows temperature-sensitive transformed phenotypes for morphology, growth in soft agar, and glucose uptake. The expression, phosphorylation, and tyrosine kinase activity of pp60v-src in S814-2 were not affected at the nonpermissive temperature, and virus rescued from this clone had wild-type transforming ability, suggesting that a cellular factor altered in S814-2 is responsible for the cellular steps of transformation after the function of pp60v-src. In addition, the cellular 36K protein, a possible candidate as a target of pp60v-src, was phosphorylated at the nonpermissive temperature in S814-2, indicating that phosphorylation of the 36K protein is not correlated with transformed phenotypes.