Role of the membrane (M) protein in endogenous inhibition of in vitro transcription by vesicular stomatitis virus

Abstract

An endogenous transcriptase inhibitor active at high concentrations of vesicular stomatitis (VS) virus was present in trypsinized whole virions but was absent from ribonucleoprotein cores containing only the L, N and NS proteins. Poly(L-glutamic acid) effectively reversed the transcriptase inhibition. Transcription under noninhibited, inhibited and poly(L-glutamic acid)-reversed conditions did not appear to greatly affect the nature of the RNA transcription product. The VS virion matrix (M) protein was purified to > 98% homogeneity and was found to have an isoelectric point of .apprx. 9.0. Purified M protein inhibited transcription by ribonucleoprotein cores, an effect that was partially reversed by poly(L-glutamic acid). Two group III temperature-sensitive (ts) mutants of VS virus (ts023) and tsG31 with lesions in the M protein exhibited little or no endogenous inhibitor activity compared with 2 wild-type strains and a group V mutant (ts045) with a lesion in the G protein. The virion M protein is probably responsible for the endogenous inhibition of in vitro RNA synthesis seen at high concentrations of VS virus.