SPLICING AS A REQUIREMENT FOR BIOGENESIS OF FUNCTIONAL 16S MESSENGER-RNA OF SIMIAN VIRUS-40

Simian virus 40 deletion mutants were constructed lacking specifically the intervening sequences for a late viral mRNA. The construction method involved the replacement of portions of the late simian virus 40 genes with the DNA segment from reverse transcription of the viral mRNAs. Restriction endonuclease cleavage and sequence analysis confirmed the precise structure of the mutant DNAs and demonstrated that they contained the genetic information for VPI, including all potential 5' ends for the late viral RNAs. Thus, the primary late transcription product(s) of this mutant should have the structure of functional 16S mRNAs. Complementation analysis as well as immunoprecipitation showed, however, that deletion of the intervening sequences from this mutant prevented the expression of VPI. The nature of this failure appears to be a defect in the posttranscriptional processing of the viral RNA. These results indicate that splicing is an essential function in the biogenesis of certain mRNAs.