title: Helper virus-independent transcription and multimerization of a satellite RNA associated with cucumber mosaic virus.
abstract: Satellite RNAs are the smallest infectious agents whose replication is thought to be completely dependent on their helper virus (HV). Here we report that, when expressed autonomously in the absence of HV, a variant of satellite RNA (satRNA) associated with Cucumber mosaic virus strain Q (Q-satRNA) has a propensity to localize in the nucleus and be transcribed, generating genomic and antigenomic multimeric forms. The involvement of the nuclear phase of Q-satRNA was further confirmed by confocal microscopy employing in vivo RNA-tagging and double-stranded-RNA-labeling assays. Sequence analyses revealed that the Q-satRNA multimers formed in the absence of HV, compared to when HV is present, are distinguished by the addition of a template-independent heptanucleotide motif at the monomer junctions within the multimers. Collectively, the involvement of a nuclear phase in the replication cycle of Q-satRNA not only provides a valid explanation for its persistent survival in the absence of HV but also suggests a possible evolutionary relationship to viroids that replicate in the nucleus.
authors.affiliation: Department of Plant Pathology & Microbiology, University of California, Riverside, California, USA.
authors.forename: Soon Ho
authors.initials: SH
authors.lastname: Choi
authors.forename: Jang-Kyun
authors.initials: JK
authors.lastname: Seo
authors.forename: Sun-Jung
authors.initials: SJ
authors.lastname: Kwon
authors.forename: A L N
authors.initials: AL
authors.lastname: Rao
mesh_terms: D021581:Active Transport, Cell Nucleus; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D017799:Cucumovirus / Q000235:genetics* / Q000378:metabolism; D006378:Helper Viruses / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D034443:RNA Transport; D019244:RNA, Satellite / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D019244:RNA, Satellite