A cellular protein with an RNA-binding activity co-purifies with viral dsRNA from mycovirus-infected Helminthosporium victoriae

A cellular protein that co-purifies with mycoviral dsRNA was isolated from the plant pathogenic fungus Helminthosporium victoriae (telomorph: Cochliob olus victoriae) infected with two viruses, the totivirus Helminthosporium v ictoriae 190S virus and the chrysovirus-like Helminthosporium victoriae 145 S virus (Hv145SV). The cellular protein, which was, designated Hv-p68, accu mulated to higher levels in virus-infected isolates compared to virus-free ones. The majority of the Hv145S dsRNAs were found in association with Hv-p 68 and not packaged in virions. Hv-p68 could also be detected as a minor co mponent of the virus capsid. Evidence is presented that Hv-p68 occurs in vi vo as an octamer and that it possesses RNA-binding activities. Based on par tial amino acid sequence analysis, Hv-p68 was shown to share significant se quence identity with alcohol oxidases from methylotrophic yeasts. Hv-p68 is proposed to play a role in viral RNA packaging/ replication and in regulat ing viral pathogenesis. (C) 2000 Academic Press.