Molecular defects caused by temperature-sensitive mutations in Semliki Forest virus nsP1

Valeria Lulla, Dorothea L Sawicki, Stanley G Sawicki, Aleksei Lulla, Andres Merits, Tero Ahola

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Alphavirus replicase protein nsP1 has multiple functions during viral RNA synthesis. It catalyzes methyltransferase and guanylyltransferase activities needed in viral mRNA capping, attaches the viral replication complex to cytoplasmic membranes, and is required for minus-strand RNA synthesis. Two temperature-sensitive (ts) mutations in Semliki Forest virus (SFV) were previously identified within nsP1: ts10 (E529D) and ts14 (D119N). Recombinant viruses containing these individual mutations reproduced the features of the original ts strains. We now find that the capping-associated enzymatic activities of recombinant nsP1, containing ts10 or ts14 lesions, were not ts. The mutant proteins and polyproteins also were membrane bound, mutant nsP1 interacted normally with the other nonstructural proteins, and there was no major defect in nonstructural polyprotein processing in the mutants, although ts14 surprisingly displayed slightly retarded processing. The two mutant viruses were specifically defective in minus-strand RNA synthesis at the restrictive temperature. Integrating data from SFV and Sindbis virus, we discuss the domain structure of nsP1 and the relative positioning of and interactions between the replicase proteins. nsP1 is suggested to contain a specific subdomain involved in minus-strand synthesis and interaction with the polymerase nsP4 and the protease nsP2.
Original languageEnglish
JournalJournal of Virology
Volume82
Issue number18
Pages (from-to)9236-9244
Number of pages9
ISSN0022-538X
DOIs
Publication statusPublished - 2008
MoE publication typeA1 Journal article-refereed

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