The linker domain of poly(rC) binding protein 2 is a major determinant in poliovirus cap-independent translation

Abstract

Poliovirus, a member of the enterovirus genus in the family Picornaviridae, is the causative agent of poliomyelitis. Translation of the viral genome is mediated through an internal ribosomal entry site (IRES) encoded within the 5′ noncoding region (5′ NCR). IRES elements are highly structured RNA sequences that facilitate the recruitment of ribosomes for translation. Previous studies have shown that binding of a cellular protein, poly(rC) binding protein 2 (PCBP2), to a major stem-loop structure in the genomic 5′ NCR is necessary for the translation of picornaviruses containing type I IRES elements, including poliovirus, coxsackievirus, and human rhinovirus. PCBP1, an isoform that shares approximately 90% amino acid identity to PCBP2, cannot efficiently stimulate poliovirus IRES-mediated translation, most likely due to its reduced binding affinity to stem-loop IV within the poliovirus IRES. The primary differences between PCBP1 and PCBP2 are found in the so-called linker domain between the second and third K-homology (KH) domains of these proteins. We hypothesize that the linker region of PCBP2 augments binding to poliovirus stem-loop IV RNA. To test this hypothesis, we generated six PCBP1/PCBP2 chimeric proteins. The recombinant PCBP1/PCBP2 chimeric proteins were able to interact with poliovirus stem-loop I RNA and participate in protein-protein interactions. We demonstrated that the PCBP1/PCBP2 chimeric proteins with the PCBP2 linker, but not with the PCBP1 linker, were able to interact with poliovirus stem-loop IV RNA, and could subsequently stimulate poliovirus IRES-mediated translation. In addition, using a monoclonal anti-PCBP2 antibody (directed against the PCBP2 linker domain) in mobility shift assays, we showed that the PCBP2 linker domain modulates binding to poliovirus stem-loop IV RNA via a mechanism that is not inhibited by the antibody.

Poly(C)-binding protein 1 (PCBP1) mediates housekeeping degradation of mitochondrial antiviral signaling (MAVS)

“…The unique property of PCBP1 was observed in knockdown studies that point to a housekeeping role for PCBP1 at the quiescent state ( Figure 6). This specificity may serve as another sound piece of evidence for divergent physiological functions of the two proteins as reported elsewhere [40][41][42][43].…”

RNA-binding protein PCBP2 modulates glioma growth by regulating FHL3

“…Most of the reports on PCBP2 have focused on its posttranscriptional and translational controls in RNA viruses. For example, PCBP2 has been reported to participate in the replication and translation of many RNA viruses, including poliovirus (15), coxsackievirus (16), and rhinovirus (17). PCBP2 can also bind to the 5′ UTR (18) and 3′ UTR (19) of the HCV gene.…”

Inhibition of Poliovirus-Induced Cleavage of Cellular Protein PCBP2 Reduces the Levels of Viral RNA Replication

“…Between domains KH2 and KH3, there is a linker region that has been shown to be an important determinant for binding of PCBP2 to stem-loop IV of poliovirus RNA (25). Previous studies have shown that PCBP2 is cleaved by the viral proteinase 3CD in the linker region between domains KH2 and KH3, removing the third KH domain.…”

“…Since RNA synthesis occurs in replication complexes, cleaved PCBP2 would be concentrated in these specified complexes, rather than occurring throughout the cell, to allow a switch to RNA replication. PCBP1, an isoform of PCBP, is thought to be generated from a retrotransposition of a fully processed PCBP2 mRNA and differs in the length of the linker region between domains KH2 and KH3 (25,27). Previous work has shown that PCBP1 is able to interact with stem-loop I of the 5= NCR but cannot bind to stem-loop IV (14,25).…”