The Pro/Hel region is indispensable for packaging non-replicating turnip yellow mosaic virus RNA, but not replicating viral RNA.
Turnip yellow mosaic virus (TYMV) is a spherical plant virus that has a single 6.3 kb positive strand RNA. The genomic RNA has a tRNA-like structure (TLS) at the 3'-end. The 3'-TLS and hairpins in the 5'-untranslated region supposedly serve as packaging signals; however, recent studies have shown that they do not play a role in TYMV RNA packaging. In this study, we focused on packaging signals by examining a series of deletion mutants of TYMV. Analysis of encapsidated viral RNA after agroinfiltration of the deletion constructs into Nicotiana benthamiana showed that the mutant RNA lacking the protease (Pro)/helicase (Hel) region was not encapsidated by the coat proteins provided in trans, implicating that a packaging signal lies in the Pro/Hel region. Examination of two Pro(-)Hel(-) mutants showed that protein activity from the Pro/Hel domains was dispensable for the packaging of the non-replicating TYMV RNA. In contrast, the mutant TYMV RNA lacking the Pro/Hel region was efficiently encapsidated when the mutant TYMV was co-introduced with a wild-type TYMV, suggesting that packaging mechanisms might differ depending on whether the virus is replicating or not.
Shin
Hyun-Il
HI
Department of Biochemistry, Chungbuk National University, Cheongju, 361-763, Korea.
Kim
Hak Yong
HY
Cho
Tae-Ju
TJ
D003001:Cloning, Molecular; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D010936:Plant Extracts; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D012327:RNA Virus Infections / Q000235:genetics* / Q000821:virology; D012367:RNA, Viral / Q000032:analysis*; D017384:Sequence Deletion / Q000235:genetics; D014026:Nicotiana / Q000821:virology; D017806:Tymovirus / Q000502:physiology*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D019065:Virus Assembly; D014779:Virus Replication
D010936:Plant Extracts; D012367:RNA, Viral; D014764:Viral Proteins; D010447:Peptide Hydrolases; D020365:RNA Helicases