The structures of the spliced mRNAs encoding polyoma virus early region proteins.

The polyoma virus early region mRNAs synthesized during productive infection of mouse cells have been characterized at the nucleotide level. One- and two-dimensional agarose gel fractionation of nuclease S1-resistant RNA-DNA hybrids was used to establish basic structures. The two splice donors and the two splice acceptors were positioned more precisely by high resolution S1-gel mapping with terminally labeled DNA probes and polyacrylamide gels. The nucleotide sequences across the three splice joints were established by cloning and sequencing partial cDNA copies of the mRNAs. In combination with data on the polyadenylated 3'-end previously published, and the detailed analysis of the capped 5'-ends presented elsewhere, the present data complete the description of a family of differentially spliced mRNAs able to encode the known early region gene products, small-T, middle-T, and large-T proteins.