The C-terminal 33 amino acids of the cucumber mosaic virus 3a protein affect virus movement, RNA binding and inhibition of infection and translation.
The capsid protein (CP) of Cucumber mosaic virus (CMV) is required for cell-to-cell movement, mediated by the 3a movement protein (MP). Deletion of the C-terminal 33 amino acids of the CMV 3a MP (in the mutant designated 3aDeltaC33 MP) resulted in CP-independent cell-to-cell movement, but not long-distance movement. RNA-binding studies done in vitro using isolated bacterially expressed MP showed that the 3aDeltaC33 MP bound RNA more strongly, with fewer regions sensitive to RNase and formed cooperatively bound complexes at lower ratios of protein : RNA than the wild-type (wt) 3a MP. Analysis of the architecture of the complexes by atomic force microscopy showed that the wt 3a MP formed a single type of complex with RNA, resembling beads on a string. By contrast, the 3aDeltaC33 MP formed several types of complexes, including complexes with virtually no MP bound or thicker layers of MP bound to the RNA. Assays showed that protein-RNA complexes containing high levels of either MP inhibited the infectivity and in vitro translatability of viral RNAs. The 3aDeltaC33 MP inhibited these processes at lower ratios of protein : RNA than the wt 3a MP, consistent with its stronger binding properties. The apparent contradiction between these inhibition data and the CP-independent cell-to-cell movement of CMV expressing the 3aDeltaC33 MP is discussed.
Kim
Sang Hyon
SH
Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK.
Kalinina
Natalia O
NO
A.N. Belozersky Institute of Physico-chemical Biology, Moscow State University, Moscow 119899, Russia.|Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK.
Andreev
Igor
I
Dept of Electronic Engineering and Physics, University of Dundee, Dundee DD1 4NH, UK.
Ryabov
Eugene V
EV
Horticulture Research International-East Malling, ME19 6BJ, UK.
Fitzgerald
Alexander G
AG
Dept of Electronic Engineering and Physics, University of Dundee, Dundee DD1 4NH, UK.
Taliansky
Michael E
ME
Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK.
Palukaitis
Peter
P
Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK.
D027462:Chenopodium / Q000821:virology; D017799:Cucumovirus / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D018625:Microscopy, Atomic Force; D010935:Plant Diseases / Q000821:virology; D018515:Plant Leaves / Q000821:virology; D053830:Plant Viral Movement Proteins; D014176:Protein Biosynthesis; D012367:RNA, Viral / Q000378:metabolism*; D017384:Sequence Deletion; D014026:Nicotiana / Q000821:virology; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D053830:Plant Viral Movement Proteins; D012367:RNA, Viral; D014764:Viral Proteins