A selectable temperature-sensitive v-src Moloney retrovirus.

We have cloned the v-src gene of ts339B77 RSV into a new Moloney-based retroviral expression vector (YN). In the resulting construct (ts339YNsrc), the ts339 gene is transcribed from the viral LTR, while a selectable resitance marker, the Tn5 neomycin phosphotransferase (neor) gene, is transcribed from an internal thymidine kinase (Tk) promoter. G418 resistance and focus formation were induced in NIH3T3 cells at comparable efficiencies within the permissive temperature range (33-37 degrees C). At 39 degrees, on the other hand, focus induction was reduced 15-fold with no corresponding decrease in expression of G418 resistance. In cells infected with ts339YNsrc, phosphoproteins were elevated and similar in pattern on SDS PAGE regardless of whether the cells were grown at the permissive or restrictive temperature. The ts339YNsrc virus will be useful for the study of effects of v-src expression, and may also be of help in identifying relevant substrates of the v-src product.