Characteristics of SV40 DNA Transcription during Lytic Infection, Abortive Infection, and in Transformed Mouse

Simian virus 40 (SV40) is a small DNA virus capable of transforming fibroblasts in vitro or producing tumors in several species of newborn rodents. This agent multiplies in primary or con-tinuous lines of African green monkey cells (permissive) and, in general, transforms cells in which productive infection is restricted (non-permissive). In transformed cells, the viral DNA does not exist as free circular or linear molecules but appears to be an integral part of the animal cell genome (Sambrook et al., 1968). SV40 thus becomes useful for studying the transcription of DNA since it exists as both free circular molecules in the nuclei of productively infected cells and as an integrated component of the DNA of some non