title: Changes in retrovirus expression in mouse mammary tumor cells in culture.
abstract: Mouse mammary tumor cells (Mm5Mt/c1) produced mouse mammary tumor virus (MMTV) (type B retrovirus) at early passages in culture. They apparently produced predominently type C retrovirus(es) at late passages in culture. The decline in MMTV production during passage was not accompanied by an apparent decrease in the synthesis or accumulation of intracellular MMTV-specific RNA. As judged by the concentration of RNA (mol/titer) x half-time (sec) of hybridization of cellular RNA with MMTV complementary DNA, the intracellular concentration MMTV-specific RNA did not change significantly during passage in culture. Since late-passage RNA, particularly polysomal poly(adenylic acid)-containing RNA, yielded lower apparent maximum hybridization of MMTV complementary DNA as compared with early-passage RNA, it was possible that the complexity or base sequence of MMTV-specific RNA in late-passage cultures was not identical with that in early-passage cultures. The data on thermal transitions of hybrids were in accord with this possibility. In contrast, the steady-state level of type C virus-specific RNA in late-passage cultures was orders of magnitude higher than that in early-passage cultures. The production of type C retrovirus(es) at later passages was apparently accompanied by increased transcription of type c retrovirus DNA.
mesh_terms: D000818:Animals; D005110:Extracellular Space / Q000382:microbiology; D005260:Female; D005786:Gene Expression Regulation; D005814:Genes, Viral; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000382:microbiology*; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D051379:Mice; D011132:Polyribosomes / Q000378:metabolism; D012367:RNA, Viral / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics*; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: D012367:RNA, Viral