Evolutionary variants of simian virus 40: Nucleotide sequence of a conserved SV40 DNA segment containing the origin of viral DNA replication as an inverted repetition

Abstract

Abstract Evolutionary variants of simian virus 40 (SV40), generated during serial passage of the virus at high multiplicity of infection, retain viral DNA sequences functioning as cis elements required for propagation, including the origin of DNA replication. To help define the SV40 origin signal, we have determined the nucleotide sequence of an SV40 segment present in a variant cloned from the 45th passage stock. The variant genome consists of SV40 DNA joined to cellular DNA and is made up of three tandemly arranged repeats of a basic DNA segment that is 28% of the length of wild-type SV40 DNA. Within each basic segment, the SV40 sequences derived from the region of the replication origin are present as an inverted repetition. On one side of the inverted sequence are 164 nucleotides of SV40 DNA and on the other side are 198 nucleotides. The variant sequence is the same as that found in parental SV40 DNA except for the presence of small tandem repeats within the variant segment. These data, together with the results of other studies of SV40 variants and deletion mutants, localize the SV40 ori signal to a segment of DNA of about 80 nucleotides between map units 0.66 and 0.68.