Abstract
Coxsackievirus B3 (CVB3) is a causative agent of viral myocarditis, meningitis and pancreatitis. CVB3 overcome their host cells by usurping the translation machinery to benefit viral gene expression. This is accomplished through alternative translation initiation in a cap independent manner at the viral internal ribosomal entry site. The 5′ untranslated region (5′UTR) of CVB3 genomic RNA is highly structured. It is the site of multiple RNA-protein and RNA-RNA interactions and it plays a critical role during translation initiation. Similar to the 5′UTR, CVB3 3′ untranslated region (3′UTR) also contains secondary structural elements consisting of three stem-loops followed by a poly (A) tail sequence. Long-range RNA-RNA interactions between 5′ and 3′ ends of some viral genomes have been observed. Because of their dual role in translation and replication, the 5′ and 3′UTRs represent promising candidates for the study of CVB3 cardiovirulence. Taking into account that efficient initiation of mRNA translation depends on a temporally and spatially orchestrated sequence of protein-protein, protein-RNA and RNA-RNA interactions, and that, at present, little is known about RNA-RNA interactions between CVB3 5′ and 3′UTRs, we aimed in the present study, to assess a possible RNA-RNA interaction between 5′ and 3′UTRs during the initiation of translation of a wild-type and a previously characterized mutant (Sabin3-like) CVB3 strains and to investigate the effect of the Sabin3-like mutation on these potential interactions. For this purpose, “Electrophoretic Mobility Shift” assays were carried out. Data obtained did not show any RNA-RNA direct interactions between the 5′- and 3′- ends. Therefore, we can suggest that the possible mechanism by which 3′UTR enhances CVB3 IRES activity may be by bridging the 5′ to the 3′ end through RNA-protein interaction and not through RNA-RNA direct contact. However, these findings need to be confirmed by carrying out further experiments.
Highlights
Coxsackievirus B3 (CVB3), a member of the family Picornaviridae, is the causative agent of virus-induced myocarditis and dilated cardiomyopathy [1,2]
CVB3 5’ and 3’ untranslated region (3’untranslated regions (UTRs)), we aimed in the present study, to assess a possible RNA-RNA
Since there is no previous report on RNA-RNA interactions of the CVB3 and in order to assess the effect of the Sabin3-like mutation on these potential interactions, we examined, in the present study, the possibility of long-range RNA-RNA interactions between the 5’ and 3’ untranslated regions during the initiation of translation of the wild-type and the mutant CVB3 strains
Summary
Coxsackievirus B3 (CVB3), a member of the family Picornaviridae, is the causative agent of virus-induced myocarditis and dilated cardiomyopathy [1,2]. The CVB3 RNA, like that of a typical picornavirus, contains a single, long open reading frame (ORF) flanked by 5’ and 3’ untranslated regions (UTRs) [3,4]. Unlike cellular messenger RNAs, translation of picornavirus genomes occurs via a cap-independent pathway. Initiation of protein synthesis in the eukaryotic cell leads to the assembly of the 80S ribosome at the start codon of the mRNA. At least two mechanisms for recruiting and positioning ribosomes on the mRNA have been described [5,6]. The primary mechanism involves the recognition of the 5’ cap structure (m7GpppN) by eukaryotic translation initiation factors (eIFs), followed by binding of the 40S ribosomal subunit and scanning downstream to the initiation codon [5,6,7]. In some mRNAs, a structural element named the “Internal Ribosome Entry
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