RNA binding activity of Nla proteinase of tobacco etch potyvirus

The C-terminal domain of Nla protein (NlaPro) from tobacco etch potyvirus (TEV) is a sequence-specific proteinase required for processing of the viral polyprotein. This proteinase also interacts with Nib, the TEV RNA-dependent RNA polymerase. NlaPro and two NlaPro-containing polyproteins (Nla and 6/Nla) were analyzed from extracts of recombinant Escherichia coli. Using RNA-protein blot and UV-crosslinking assays, NlaPro and the NlaPro-containing polyproteins were shown to possess RNA-binding activity. NlaPro bound nonspecifically to several RNAs, including plus-and minus-strands of the TEV 5' and 3' noncoding regions. Saturation binding data obtained using the UV-crosslinking assay were consistent with a possible cooperative RNA-binding activity of NlaPro. In addition, the RNA-binding activities of NlaPro and full-length Nla protein were similar. Based on its RNA-binding activity and other known functions, NlaPro or a NlaPro-containing polyprotein is proposed to serve one or more direct roles during TEV RNA synthesis. (C) 1997 Academic Press.