An Internal Ribosome Entry Site Directs Translation of the 3′-Gene from Pelargonium Flower Break Virus Genomic RNA: Implications for Infectivity

被引:19
作者
Fernandez-Miragall, Olga [1 ]
Hernandez, Carmen [1 ]
机构
[1] Univ Politecn Valencia, Consejo Super Invest Cient, Inst Biol Mol & Celular Plantas, E-46071 Valencia, Spain
关键词
CAP-INDEPENDENT TRANSLATION; 5' UNTRANSLATED REGION; PICORNAVIRUS IRES ELEMENTS; PLANT VIRAL RNAS; 3'-UNTRANSLATED REGION; MESSENGER-RNA; COAT PROTEIN; IN-VITRO; NONTRANSLATED REGION; ENHANCES TRANSLATION;
D O I
10.1371/journal.pone.0022617
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Pelargonium flower break virus (PFBV, genus Carmovirus) has a single-stranded positive-sense genomic RNA (gRNA) which contains five ORFs. The two 59-proximal ORFs encode the replicases, two internal ORFs encode movement proteins, and the 39-proximal ORF encodes a polypeptide (p37) which plays a dual role as capsid protein and as suppressor of RNA silencing. Like other members of family Tombusviridae, carmoviruses express ORFs that are not 59-proximal from subgenomic RNAs. However, in one case, corresponding to Hisbiscus chlorotic ringspot virus, it has been reported that the 39-proximal gene can be translated from the gRNA through an internal ribosome entry site (IRES). Here we show that PFBV also holds an IRES that mediates production of p37 from the gRNA, raising the question of whether this translation strategy may be conserved in the genus. The PFBV IRES was functional both in vitro and in vivo and either in the viral context or when inserted into synthetic bicistronic constructs. Through deletion and mutagenesis studies we have found that the IRES is contained within a 80 nt segment and have identified some structural traits that influence IRES function. Interestingly, mutations that diminish IRES activity strongly reduced the infectivity of the virus while the progress of the infection was favoured by mutations potentiating such activity. These results support the biological significance of the IRES-driven p37 translation and suggest that production of the silencing suppressor from the gRNA might allow the virus to early counteract the defence response of the host, thus facilitating pathogen multiplication and spread.
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页数:12
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