Deoxyribonucleic Acid Replication in Simian Virus 40-Infected Cells

Abstract

Purified simian virus 40 (SV40) virions, grown in primary African green monkey kidney cells labeled prior to infection with ³ H-thymidine, contain a variable quantity of ³ H-labeled deoxyribonucleic acid (DNA). This DNA is resistant to deoxyribonuclease, sediments at 250 S , and is enclosed in a particle that can be precipitated with SV40-specific antiserum. DNA-DNA hybridization experiments demonstrate that this ³ H-labeled component in purified SV40 virions is cellular DNA. When this ³ H-labeled DNA is released from purified virus with sodium dodecyl sulfate, it has an average sedimentation constant of 14 S . Sedimentation through neutral and alkaline sucrose gradients shows that this 14 S DNA is composed of a collection of different sizes of DNA molecules that sediment between 11 and 15 S . As a result of this size heterogeneity, SV40 virions containing cellular DNA (pseudovirions) have a variable DNA to capsid protein ratio and exhibit a spectrum of buoyant densities in a CsCl equilibrium gradient. Pseudovirions are enriched, relative to true virions, on the lighter density side of infectious SV40 virus banded to equilibrium in a CsCl gradient. Little or no cellular DNA was found in purified SV40 virus preparations grown in BSC-1 or CV-1 cells.