An RNA-dependent RNA Polymerase Associated with the Filamentous Nucleoproteins of Rice Stripe Virus

Abstract

SUMMARYFilamentous particles of rice stripe virus (RSV) were found to be associated with an RNA-dependent RNA polymerase activity. The enzyme catalysed the synthesis in vitro of single-and double-stranded RNAs corresponding in size with RNA found in RSV particles, as well as two other dsRNAs with mol. wt. of 1.0 × l06 and 0.56 × 106. The RSV polymerase activity required Mg 2+, Mn 2+ or Fe E+ but not Na +, K + or NH4 + which were inhibitory at concentrations of more than 50 mM. The optimum pH of the polymerase was around 8.0 at the optimum temperature, 40 °C. Detergent treatment of RSV particles did not enhance the polymerase activity. Purified RSV particles contained a minor polypeptide (mol. wt. 230000) as well as coat protein; the former may be the RSV polymerase. The taxonomy of RSV is discussed in relation to enveloped animal viruses with negative-stranded RNA, which also contain an RNAdependent RNA polymerase in virus particles.

Nucleotide sequence and possible ambisense coding strategy of rice stripe virus RNA segment 2

“…1990). RSV and rice grassy stunt tenuivirus contain the RNA-dependent RNA polymerase as an integral component of the virus particles (Toriyama, 1986a(Toriyama, , 1987. A soluble protein fraction containing the nucleocapsid protein and a minor viral protein of 230K exhibits RNA polymerase activity in the presence of model RNA templates with the 3' conserved sequence (Barbier et al, 1992).…”

“…In order to determine the coding strategies of the two large RNAs of RSV, we are attempting to sequence the RSV genome (Zhu et al, 1991(Zhu et al, , 1992. We report here the complete nucleotide sequence of RNA 2 of RSV isolate T. Purification of RSV isolate T nucleoprotein particles and the preparation of RNA were carried out as described previously (Toriyama, 1986a;Toriyama & Watanabe, 1989). Either ssRNA 2 purified from the agarose gel or a mixture of RNAs 2, 3 and 4 were used as templates for the cDNA synthesis.…”

Complementarity Between the 5'- and 3'-terminal Sequences of Rice Stripe Virus RNAs

“…A similar relationship between encapsidated ssRNA and dsRNA was shown for another isolate of RSV and for maize stripe tenuivirus (Ishikawa et al, 1989;Falk et al, 1989). RSV particles also contain a nucleocapsid protein of Mr 32000 and a minor protein of Mr 230000 (Toriyama, 1986). The nucleoproteins of RSV and rice grassy stunt tenuivirus are also associated with an RNA-dependent RNA polymerase activity (Toriyama, 1986(Toriyama, , 1987.…”

“…We suggest that the terminal complementary sequences cause RSV RNAs to form panhandles. Another resemblance to negative-sense viruses is that particles of RSV and rice grassy stunt virus are associated with a highly active RNA-dependent RNA polymerase (Toriyama, 1986(Toriyama, , 1987.…”

“…The nucleoproteins of RSV and rice grassy stunt tenuivirus are also associated with an RNA-dependent RNA polymerase activity (Toriyama, 1986(Toriyama, , 1987. Toriyama (1986) suggested that the genomic RNAs have negative polarity, and that the Mr 230000 protein may be an RNA polymerase.…”