title: Evidence for alternate states of Cucumber mosaic virus replicase assembly in positive- and negative-strand RNA synthesis.
abstract: Cucumber mosaic virus (CMV) encodes two viral replication proteins, 1a and 2a. Accumulating evidence implies that different aspects of 1a-2a interaction in replication complex assembly are involved in the regulation of virus replication. To further investigate CMV replicase assembly and to dissect the involvement of replicase activities in negative- and positive-strand synthesis, we transiently expressed CMV RNAs and/or proteins in Nicotiana benthamiana leaves using a DNA or RNA-mediated expression system. Surprisingly, we found that, even in the absence of 1a, 2a is capable of synthesizing positive-strand RNAs, while 1a and 2a are both required for negative-strand synthesis. We also report evidence that 1a capping activities function independently of 2a. Moreover, using 1a mutants, we show that capping activities of 1a are crucial for viral translation but not for RNA transcription. These results support the concept that two or more alternate states of replicase assembly are involved in CMV replication.
authors.affiliation: Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea.
authors.forename: Jang-Kyun
authors.initials: JK
authors.lastname: Seo
authors.forename: Sun-Jung
authors.initials: SJ
authors.lastname: Kwon
authors.forename: Hong-Soo
authors.initials: HS
authors.lastname: Choi
authors.forename: Kook-Hyung
authors.initials: KH
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D017799:Cucumovirus / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D018515:Plant Leaves / Q000821:virology; D012367:RNA, Viral / Q000096:biosynthesis*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000821:virology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D050505:Mutant Proteins; D012367:RNA, Viral; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase