Structure of the adenovirus 2 early mRNAs.

We have defined the structure of adenovirus 2 (Ad2) cytoplasmic RNAs produced during the early phase of infection. Hybrids between cytoplasmic RNA and DNA restriction fragments of the viral genome were digested with endonuclease S1 or exonuclease VII, and the products were analyzed by gel electrophoresis. Seven abundant cytoplasmic RNAs (assumed to be mRNAs) were identified, and all have a spliced structure. Different mRNAs produced from a single transcriptional unit contain extensively overlapping sequences, and differ from each other by the pattern in which genome sequences are spliced together. The structures of the early Ad2 mRNAs are consistent with a model for mRNA biosynthesis in which an initial transcript is processed into a mature mRNA by "splicing out" internal sequences. The pattern of spliced mRNAs produced from the early region responsible for the transforming activity of Ad2 resembles the splicing pattern of the oncogenic early mRNAs of simian virus 40 (SV40). This fact, in conjunction with recent DNA sequencing results, leads us to suggest that, like the SV40 tumor antigens, the polypeptides encoded by these Ad2 mRNAs have an identical amino acid sequence at their N terminal ends, but have different C terminal sequences.