Regulation of RNA Translation in Potato Virus X RNA–CoatProtein Complexes: The Key Roleof the N-Terminal Segment of the Proteinстатья
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Аннотация:Abstract
—The efficiency of in vitro translation of the potato virus X (PVX) RNA was studied for viral ribonucleoprotein
complexes (vRNP) assembled from the genomic RNA and the viral coat protein (CP). In vRNP
particles the 5'-proximal RNA segments were encapsidated into the CP, which formed helical headlike structures
differing in length. Translation of the PVX RNA was completely suppressed upon incubation with PVX
CP and was activated within vRNPs assembled in vitro with two CP forms, differing in the modification of the
N-terminal peptide containing the main phosphorylation site(s) for Thr/Ser protein kinases. It was shown that
CP phosphorylation activates RNA translation within vRNPs and that the removal of the N-terminal peptide of
CP suppresses activation, but CP still acts as a translational suppressor. This fact made it possible to suppose
that the replacement of Ser/Thr by amino acid residues that are not subject to phosphorylation in the N-terminal
peptide of CP of the mutant PVX (PVX-ST) completely inhibits RNA translation within vRNP. However,
experiments disproved this assumption: PVX-ST RNA was efficiently translated within native virions, RNA of
the wild-type (wt) PVX was efficiently translated in heterogeneous vRNP (wtRNA + PVX-ST CP), and the
opposite result (repression of translation) was obtained for another heterogeneous vRNP (PVX-ST RNA +
wtCP). Therefore, the N-terminal CP peptide located on the surface of the PVX virion or vRNP particles plays
a key role in the activation of viral RNA translation.