title: Pokeweed antiviral protein inhibits brome mosaic virus replication in plant cells.
abstract: Pokeweed antiviral protein (PAP) is a ribosome-inactivating protein isolated from the pokeweed plant (Phytolacca americana) that inhibits the proliferation of several plant and animal viruses. We have shown previously that PAP and nontoxic mutants of PAP can directly depurinate brome mosaic virus (BMV) RNA in vitro, resulting in reduced viral protein translation. Here we expand on these initial studies and, using a barley protoplast system, demonstrate that recombinant PAP and nontoxic mutants isolated from E. coli are able to reduce the accumulation of BMV RNAs in vivo. Pretreatment of only BMV RNA3 with PAP prior to transfection of barley protoplasts reduced the accumulation of all BMV RNAs, with a more severe effect on subgenomic RNA4 levels. Using in vitro RNA synthesis assays, we show that a depurinated template causes the BMV replicase to stall at the template nucleotide adjacent to the missing base. These results provide new insight into the antiviral mechanism of PAP, namely that PAP depurination of BMV RNA impedes both RNA replication and subgenomic RNA transcription. These novel activities are distinct from the PAP-induced reduction of viral RNA translation and represent new targets for the inhibition of viral infection.
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Picard
authors.forename: C Cheng
authors.initials: CC
authors.lastname: Kao
authors.forename: Katalin A
authors.initials: KA
authors.lastname: Hudak
mesh_terms: D001483:Base Sequence; D017795:Bromovirus / Q000187:drug effects* / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D001467:Hordeum / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000494:pharmacology*; D029603:Phytolacca / Q000737:chemistry / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000494:pharmacology*; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology; D054789:Ribosome Inactivating Proteins, Type 1; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D010940:Plant Proteins; D012367:RNA, Viral; D011994:Recombinant Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D009699:N-Glycosyl Hydrolases; C024275:pokeweed antiviral protein