DNA sequence analysis of simian virus 40 mutants with deletions mapping in the leader region of the late viral mRNA's: mutants with deletions similar in size and position exhibit varied phenotypes

Abstract

The nucleotide sequences of 10 viable yet partially defective deletion mutants of simian virus 40 were determined. The deletions mapped within, and, in many cases, 59 to, the predominant leader sequence of the late viral mRNA9s. They ranged from 74 to 187 nucleotide pairs in length. Six of the mutants had lost the sequence that corresponds to the "cap" site (59 terminus) of the most abundant class of 16S mRNA9s. One of these mutants had a deletion that extended 103 nucleotide pairs into the region preceding this primary cap site and, therefore, was missing many secondary cap sites as well. A seventh mutant lacked the entire major 16S leader sequence except for the first six nucleotides at its 59 end and the last nine at its 39 end. Although these mutants differed in the size and position of their deletions, we were unable to discover any simple correlations between their growth characteristics and their DNA sequences. This finding indicates that the secondary structures of the RNA transcripts may play a more important role than the exact nucleotide sequence of the RNAs in determining how they function within the cell. Images