Mutational alterations within the simian virus 40 leader segment generate altered 16S and 19S mRNA's

Abstract

The structures of the late cytoplasmic RNA made after infection [of African green monkey kidney CV-1 cells] with wild-type SV-40 and a set of viable mutants, 4 of which have deletions and 1 an insertion within the nucleotide sequence specifying the leader segment of the 16S and 19S mRNA, were analyzed. SV-40 16S and 19S mRNA made during infections with wild-type virus are heterogeneous with respect to the map location of their 5'' ends and possibly in the nucleotide sequence comprising the leader segments. Spliced 16S and 19S mRNA are made during infections with each of the mutants although, in some cases, the ratio of 19S to 16S mRNA species is reduced. The deletion or insertion of nucleotides within the DNA segment defined by map position 0.70-0.75 causes striking alterations in the types of leader structures in the late mRNA. Many of the late RNA leader segments produced after infection with the mutants appear to be multiply spliced, i.e., instead of the major 200- to 205-nucleotide-long leader segment present in wild-type 16S mRNA, the RNA produced by several of the deletion mutants have leaders with short discontiguous segments.