Sequence analysis of adenovirus DNA: IV. The genomic sequences encoding the common tripartite leader of late adenovirus messenger RNA

Abstract

The regions on the adenovirus type 2 genome which encode the three segments of the common tripartite leader of late adenovirus messenger RNA have been identified and sequenced. Each segment of the tripartite leader is specified by a contiguous sequence of DNA. A comparison between the established sequences and the sequence of the 5′ non-coding region of the hexon mRNA (Akusjärvi & Pettersson, 1979) suggests that the first leader segment (map position 16.3) is 42 nucleotides long, including the m 7G, the second (map position 19.6) 71 nucleotides long and the third segment (map position 26.5) 89 nucleotides long. These estimates are, however, in all cases ambiguous due to the presence of short tandemly repeated sequences at the borders of each individual intervening sequence. These repeats makes it impossible to pin-point the exact position where the splicing event has taken place. A comparison of the six junction regions where leaders are connected to intervening sequences shows that they have similar although not identical sequences. All junctions contain the trinucleotide GGT at the 5′ side and the dinucleotide A-G at the 3′ side of the intervening sequence. Furthermore the established junction sequences exhibit a striking similarity to the corresponding regions of eukaryotic genes, in particular to the sequences which flank the large intervening sequence in the gene for mouse β maj-globin (Konkel et al., 1978). Two regions in the promoter for late adenovirus transcription at map position 16.3 share homology with the corresponding region of the gene for β maj-globin (Konkel et al., 1978). These two regions include sequences which precede and overlap the initiation site for late adenovirus transcription and the sequence T-A-T-A-A-A-A which is present 24 nucleotides leftwards of the cap site. This heptanucleotide resembles a sequence found in prokaryotic promoters (Pribnow, 1975).