Demethylation and expression of murine mammary tumor proviruses in mouse thymoma cell lines.

摘要: Abstract Murine mammary tumor virus (MMTV) expression is analyzed in a T-lymphoid cell line (T1M1) sensitive to the killing effect of glucocorticoids and two its variants, one resistant (T1M1r) supersensitive (T1M1ss) glucocorticoid-induced lymphocytolysis. In T1M1 line, MMTV expressed induced approximately 10-fold by short treatment with dexamethasone. Southern blot analyses restriction enzyme digests DNA from cells reveal three proviruses similar those normal C57BL mouse tissue. T1M1ss which has retained functional glucocorticoid receptors, mRNA inducible glucocorticoids, while induction reduced T1M1r defective receptors. Moreover, expresses strikingly elevated basal level absence hormone. No rearrangements or superinfection have occurred but all regions containing 5'-long terminal repeats are demethylated variant although other sites provirus remain methylated. Because this was selected prolonged dexamethasone, these observations raise possibility that continuous transcription during selection can result demethylation long-terminal-repeat sequences.