Splicing of the late mRNAs of polyoma virus does not occur in the cytoplasm of the infected cell.

The three mRNAs that encode the capsid proteins of polyoma virus are produced by the excision of different sequences from continuous transcripts of the L strand of viral DNA. All three of the mRNAs have long half lives, and the larger species are not converted to the smaller ones to any measurable extent within the cytoplasm. Therefore the cytoplasmic proportions of late polyoma mRNAs are predetermined by splicing that is confined to the nucleus of the infected cell and which is complete by the time that mRNA is transported to the cytoplasm.