Deletion mutants of simian virus 40 defective in biosynthesis of late viral mRNA.

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Abstract
Deletion mutants of SV-40 defective in late gene functions were examined for genetic elements that control the biosynthesis of the viral mRNA. Mutant-specific RNA from infected [African green monkey kidney AGMK] cells was identified by CH3Hg(OH)/agarose gel electrophoresis and mapped by the nuclease S1 technique. Altered RNA species, shortened by a size equivalent to the deletion region, can be detected in cells infected with these mutants lacking sequences within the body RNA segments. Mutants that lack the 5''-end of the body sequences (a splice junction) fail to accumulate the respective shortened RNA species. In particular, mutant dl-2301 whose deletion includes both the leader and body splice junctions plus the intervening sequences, exhibits a polar effect on a distal gene. Whereas the late region of dl-2301 can be transcribed normally, the mutant defect appears to be associated with little or no accumulation of the mutant-specific late RNA in the infected cells. Splice junctions or the intervening sequences, or both, in the viral genome are probably control signals for post-transcriptional processing of the viral RNA.