title: The mitogenic activity of pp60v-src, the oncogenic protein product of the src gene of avian sarcoma virus, is independent of external serum growth factors.
abstract: The oncogenic pp60v-src product of ASV (avian sarcoma virus) is shown to be a potent endogenous mitogen, which, unlike mitogens such as PDGF (platelet derived growth factor), is able to stimulate host cell proliferation without the help of other growth factors. Thus, NRK rat cells, infected with a temperature-sensitive ASV mutant which produces an abnormally thermolabile pp60v-src, became proliferatively quiescent at a pp60v-src-inactivating 40 degrees C in medium containing either 0.2% calf serum or no serum at all. Adding PDGF stimulated the quiescent tsASV-NRK cells at 40 degrees C to initiate DNA replication in medium containing 0.2% serum, but not in serum-free medium. By contrast, activating internal pp60v-src by dropping the temperature to a permissive 36 degrees C stimulated these quiescent cells to transit G1, initiate DNA replication and to enter mitosis even in serum-free medium. Thus, relative to PDGF, endogenous pp60v-src behaves as a complete mitogen.
mesh_terms: D000818:Animals; D002460:Cell Line; D004261:DNA Replication / Q000187:drug effects; D006133:Growth Substances / Q000494:pharmacology*; D008934:Mitogens; D015688:Oncogene Protein pp60(v-src); D051381:Rats; D013696:Temperature; D013997:Time Factors; D014764:Viral Proteins / Q000494:pharmacology*
chemical_list: D006133:Growth Substances; D008934:Mitogens; D014764:Viral Proteins; D015688:Oncogene Protein pp60(v-src)