Studies on the occurrence of high molecular weight adenovirus type 2 DNA in productively infected cells

Abstract

Newly synthesized viral DNA in human cells productively infected with adenovirus type 2 (Ad2) occurs in four size classes which can be separated by zone velocity sedimentation in alkaline sucrose density gradients. The 34 S size class represents unit-length Ad2 DNA and the <20 S size class consists of fragments of viral DNA. The high molecular weight size classes, >100 S and 50–90 S, contain viral DNA sequences integrated in cellular DNA. The factors which influence the amount and composition of the high molecular weight viral DNA have been investigated. The proportion of Ad2 DNA sequences in 50–90 S DNA varies from one cell line to another and is enhanced in rapidly growing cultures relative to confluent monolayers of KB cells. An increased multiplicity of infection also results in a higher proportion of viral sequences in the 50–90 S size class. KB cells infected with Ad2 inactivated by ultraviolet light and unable to replicate its DNA, however, contain nearly the same amount of high molecular weight viral DNA as cells infected with fully infectious virus. There is much evidence from previous work that the high molecular weight form of viral DNA represents viral sequences linked to cellular DNA. The present data suggest that the synthesis of high molecular weight viral DNA does not depend on the concurrent synthesis of 34 S viral DNA but requires active cell growth, possibly cellular DNA replication.