Region E3 of human adenoviruses; differences between the oncogenic adenovirus-3 and the non-oncogenic adenovirus-2.

The nucleotide sequence of a 4379-bp-long DNA segment, located between map coordinates 76.5 and 89.2 in the Ad3 genome, was established. The segment includes the entire early transcription unit 3 (E3) and the 3'-part of the gene for the late polypeptide pVIII. The established sequence was compared to the sequence of the corresponding region in the Ad2 genome [Hérissé et al., Nucl. Acids Res. 8, (1980) 2173-2192; Hérissé and Galibert, Nucl. Acids Res. 9, (1981) 1229-1249]. Although Ad2 and Ad3 belong to different serological and oncogenic subgroups, their E3 regions are well conserved (55-60% homology). In total, the E3 region of Ad3 appears to encode eight to nine different polypeptides many of which are likely to be membrane-associated. The most conspicuous difference between the E3 regions of Ad2 and Ad3 is the presence of a 950-bp-long A + T-rich insert in the Ad3 sequence. This insert contains two open reading frames, each encoding a polypeptide with a predicted Mr of about 20,000. The mRNAs encoding these novel polypeptides were identified by S1 nuclease analysis.