Integration and transcription of mouse mammary tumor virus DNA in rat hepatoma cells.

Abstract

Rat hepatoma cells infected with mouse mammary tumor virus (MMTV) acquire viral DNA that becomes covalently linked to the cell DNA. Using restriction endonucleases and the DNA transfer procedure of Southern [Southern , E.M. (1975) J. Mol. Biol. 98, 503--517], we have studied the sites in cellular DNA into which MMTV DNA inserts. These experiments indicate that: (i) there are many sites in cell DNA into which MMTV DNA integrates; (ii) the junctions between viral and cellular DNA occur within a limited portion of the viral genome, (iii) clones that contain MMTV DNA do not necessarily produce viral RNA; and (iv) the extent of transcription and glucocorticoid responsiveness of MMTV proviruses may be dependent on the site(s) in cell DNA in which the viral DNA resides.