Virus-associated RNAs of naturally occurring strains and variants of group C adenoviruses

Abstract

We compared the sequences of the virus-associated (VA) RNAs of group C adenoviruses, serotypes 1, 2, 5, and 6, and of three variants of adenovirus type 2 (Ad2) selected for loss of the BamHI restriction site in the VA RNA, gene. In the naturally occurring strains, VA RNA, exists in two forms which differ by two nucleotides: one form is found in Ad2 and Ad6, and the other is found in Adl and Ad5. There are three sites of variation in VA RNA,,, the Adl, Ad2, and Ad5 forms each differing from Ad6 VA RNA5 at one of the positions. One of the selected variants has a four-base duplication within the BantHI cleavage site, whereas the two others have acquired a VA RNA, sequence indistinguishable from that of Ad5. The findings are interpreted in terms of the secondary structures of the VA RNAs and the interrelationships among the viruses.

Effects of mutations in stem and loop regions on the structure and function of adenovirus VA RNAI.

“…Several lines of evidence support this model. First, it accommodates the two single-base changes found in AdS (and Adl) without the disruption of pairing implicit in the computer-assisted predictions (Mathews and Grodzicker, 1981). Second, the effects of mutations are broadly consistent with the model: as pointed out above, this is strikingly evident with the dll deletion ( Figure 7C).…”

“…Structural analysis of dll RNA confirmed that the distal half of stem 4 had become sensitive to single-strand specific nucleases, as expected, whereas the conformation of the rest of the molecule was largely unchanged. Viruses containing the pA2dl2 deletion, or a deletion of nt 70-76 in the distal reaches of stem 4, are fully viable , as are the mutant var-3, which contains a four-base insertion between nt 71 and 72, and the naturally occurring Adl and Ad5 serotypes which both contain a substitution at nt 72 (Mathews and Grodzicker, 1981). From these data, we conclude that the distal portion of stem 4 is dispensable, and that mutations in this region do not disrupt structures elsewhere in the molecule.…”

“…Its electrophoretic behavior in gels suggests that it is highly structured, and several possible secondary structures have been advanced on the basis of sequence studies (Ohe and Weissman, 1971), computer-assisted predictions (Zain et al, 1979;Akusjarvi et al, 1980), and nuclease digestion experiments (Monstein and Philipson, 1981). All other adenoviruses studied so far have at least one VA RNA species, and where tested they are capable of rescuing protein synthesis to some degree (Mathews and Grodzicker, 1981;Engler et al, 1983;Larsson et al, 1986a,b;Shu et al, 1986). Like the VA RNA,, species of Ad2, they can also be folded to form hypothetical stem-loop structures, but in no case has the structure been confirmed experimentally.…”

Role of the apical stem in maintaining the structure and function of adenovirus virus-associated RNA

“…The two mutants possessing an undisturbed secondary structure, lslb and lslc, rescue protein synthesis in Ad5dl331-infected cells as efficiently as wild-type VA RNA,. Together with earlier findings (15,18), this suggests that there is no specific sequence requirement in the apical stem. The other mutants in this series, Isla, lsld, and Isle, were about half as active as wild-type VA RNA in the rescue assay.…”

Regulation of Protein Synthesis in Virus-Infected Animal Cells

“…Further experiments will be needed to pinpoint the essential region(s) in VA-RNAI. A second adenovirusencoded species called VA-RNAI, rescues translation far less efficiently than VA-RNA, (Thimmappaya et al, 19821, and VA-RNAII appears less extensively base paired (Mathews and Grodzicker, 1981).…”