Structure of two spliced mRNAs from the transforming region of human subgroup C adenoviruses

Abstract

The papova viruses and the human adenoviruses are widely used as a model system to study cell transformation in vitro. In subgroup C human adenoviruses, fragment HpaI-E, which comprises as little as 4.5% of the adenovirus type 5 (ad5) DNA, is sufficient for transformation of rat embryo cells¹. Analysis of messenger RNAs (mRNAs) from the transforming region of adenoviruses type 2 (ad2) has identified several spliced mRN A species^2–4. Promoter mapping studies indicate that the leftmost early region contains two separate transcription units, E1A and E1B (ref. 5) (Fig. 1a). Region E1A is approximately equivalent HpaI-E. The complete nucleotide sequence of the HpaI-E fragment of ad5 was recently reported⁶. However, the spliced nature of early adenovirus mRNAs prevents a prediction of the amino acid sequence of the corresponding polypeptides directly from the DNA sequence. To study the structure of early ad2 mRNAs at the nucleotide level, we have used molecular cloning procedures to amplify the appropriate mRNA sequences. In this report, clones corresponding to the 12S and 13S mRNA from region E1A (Fig. 1c) have been isolated and characterised by hybridisation and sequence analysis. Our results enable us to predict the primary sequence of two related polypeptides from region E1A of human subgroup C adenoviruses.