Roles of nonstructural polyproteins and cleavage products in regulating Sindbis virus RNA replication and transcription.

摘要: Using vaccinia virus to express Sindbis (SIN) nonstructural proteins (nsPs) and template RNAs, we showed previously that synthesis of all three viral RNAs occurred only during expression either the entire coding region or polyprotein precursors P123 P34. In this report, system was used cleavage-defective polyproteins nsP4 containing various N-terminal extensions directly examine roles P34 in RNA replication. Replication subgenomic mRNA transcription coexpression which cleavage blocked at both 1/2 2/3 sites. For polyproteins, however, ratio genomic decreased, suggesting cleavages are required for efficient transcription. These studies indicate uncleaved can function as a component replicase capable synthesizing plus- minus-strand RNAs. contrast, unable replication, even complementation experiments were provided by nsP4. A whose site not altered could replication presence an active nsP2 protease. Although nsP4, putative polymerase, with P123, addition 22 upstream residues allowed occur. data show conserved domains nsP3 polymerase do need be present form functional plus-strand replicase-transcriptase suggest protease cleavable 3/4 correlates virus-specific species.