title: Biological and biochemical studies of cells transformed by simian virus 40 temperature-sensitive gene A mutants and A mutant revertants.
abstract: The growth properties of hamster cells transformed by wild-type Simian virus 40 (SV40), by early SV40 temperature-sensitive mutants of the A complementation group, and by spontaneous revertants of these mutants were studied. All of the tsA mutant-transformed cells were temperature sensitive in their ability to form clones in soft agar and on monolayers of normal cells except for CHLA-30L1, which was not temperature sensitive in the latter property. All cells transformed by stable revertants of well-characterized tsA mutants possessed certain growth properties in common with wild-type-transformed cells at both temperatures. Virus rescued from tsA transformants including CHLA30L1 was temperature sensitive for viral DNA replication, whereas that rescued from revertant and wild-type transformants was not thermolabile in this regard. T antigen present in crude extracts of tsA-transformed cells including CHLA30L1, grown at 33 degreeC, was temperature sensitive by in vitro immunoassay, whereas that from wild-type-transformed cells was relatively stable. T antigen from revertant transformants was more stable than the tsA protein. Partially purified T antigen from revertant-transformed cells was nearly as stable as wild-type antigen in its ability to bind DNA after heating at 44 degrees C, whereas T antigen from tsA30 mutant-transformed cells was relatively thermolabile. These results further indicate that T antigen is a product of the SV40 A gene. Significantly more T antigen was found in extracts of CHLA30L1 grown to high density at the nonpermissive temperature than in any other tsA-transformed cell similarly grown. This is consistent with the suggestion that the amount of T antigen synthesized in CHLA30L1 is large enoughto allow partial expression of the transformed phenotype at the restrictive temperature. Alternatively, the increase in T antigen concentration may be secondary to one or more genetic alterations that independently affect the transformed phenotype of these cells.
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000032:analysis; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D006224:Cricetinae; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis; D005796:Genes; D006649:Histocompatibility Antigens / Q000032:analysis; D006358:Hot Temperature; D009154:Mutation; D013539:Simian virus 40 / Q000254:growth & development* / Q000276:immunology / Q000378:metabolism; D013696:Temperature; D014779:Virus Replication
chemical_list: D000956:Antigens, Viral; D004279:DNA, Viral; D006649:Histocompatibility Antigens