title: Conditions leading to the establishment of the N (a gene dependent) and A (a gene independent) transformed states after polyoma virus infection of rat fibroblasts.
abstract: Infection of normal rat fibroblasts (FR 3T3) with the early tsa mutant of polyoma virus may lead to either the A or the N phenotype, tsa-A transformants, originally derived by agar selection, are not temperature dependent for maintenance of the transformed phenotype, whereas tsa-N transormants revert at high temperature to normal growth control. A transformants did not result from an independent cellular mutation selected in agar medium, but rather from a transformation process distinct from that leading to the N state. It occurred in both liquid and agar media when the infected cells were maintained under growth-restricting conditions, such as absence of anchorage and contact inhibition at confluency. N transformation occurred in cells maintained in active growth after virus infection (sparse cultures on a solid substratum). Physiological conditions during a critical period after virus infection thus appear to be a crucial parameter of the transformation process.
mesh_terms: D000362:Agar; D000818:Animals; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002472:Cell Transformation, Viral; D002999:Clone Cells; D005347:Fibroblasts; D009154:Mutation; D010641:Phenotype; D011120:Polyomavirus / Q000254:growth & development*; D051381:Rats; D013696:Temperature
chemical_list: D000362:Agar