Cleavage of Poly(A)-Binding Protein by Enterovirus Proteases Concurrent with Inhibition of Translation In Vitro

Abstract

Many enteroviruses, members of the familyPicornaviridae, cause a rapid and drastic inhibition of host cell protein synthesis during infection, a process referred to as host cell shutoff. Poliovirus, one of the best-studied enteroviruses, causes marked inhibition of host cell translation while preferentially allowing translation of its own genomic mRNA. An abundance of experimental evidence has accumulated to indicate that cleavage of an essential translation initiation factor, eIF4G, during infection is responsible at least in part for this shutoff. However, evidence from inhibitors of viral replication suggests that an additional event is necessary for the complete translational shutoff observed during productive infection. This report examines the effect of poliovirus infection on a recently characterized 3′ end translational stimulatory protein, poly(A)-binding protein (PABP). PABP is involved in stimulating translation initiation in lower eukaryotes by its interaction with the poly(A) tail on mRNAs and has been proposed to facilitate 5′-end–3′-end interactions in the context of the closed-loop translational model. Here, we show that PABP is specifically degraded during poliovirus infection and that it is cleaved in vitro by both poliovirus 2A and 3C proteases and coxsackievirus B3 2A protease. Further, PABP cleavage by 2A protease is accompanied by concurrent loss of translational activity in an in vitro-translation assay. Similar loss of translational activity also occurs simultaneously with partial 3C protease-mediated cleavage of PABP in translation assays. Further, PABP is not degraded during infections in the presence of guanidine-HCl, which blocks the complete development of host translation shutoff. These results provide preliminary evidence that cleavage of PABP may contribute to inhibition of host translation in infected HeLa cells, and they are consistent with the hypothesis that PABP plays a role in facilitating translation initiation in higher eukaryotes.

Chapter 9 Viral Strategies to Subvert the Mammalian Translation Machinery

“…It has been shown that infection of cells with the picornaviruses PV and coxsackie virus B3 (CVB3) results in the cleavage of PABP. 50,51 Furthermore, it was demonstrated that the viral 2A proteases directly cleaved PABP between M487-G488. 50,51 PABP contains four RNA recognition motifs (RRMs) that participate in eIF4G-and RNA-binding and a conserved C-terminal domain that interacts with other factors such as eIF4B.…”

“…50,51 Furthermore, it was demonstrated that the viral 2A proteases directly cleaved PABP between M487-G488. 50,51 PABP contains four RNA recognition motifs (RRMs) that participate in eIF4G-and RNA-binding and a conserved C-terminal domain that interacts with other factors such as eIF4B. 52,53 Cleavage of PABP by the picornavirus 2A proteases separates the RRMs from the C-terminus and results in inhibition of protein synthesis, although PABP cleavage does not fully correlate with shutoff.…”

Translational control by viral proteinases

“…What else could have been missing from the shutoff model? Alternatively, it has been shown that PABP is also cleaved in PV-and CVB3-infected cells (Joachims et al, 1999;Kerekatte et al, 1999). Importantly, since cleavage of PABP is blocked in PV infections carried out with 2 mM guanidine-HCl, PABP cleavage also may be an important "missing event" in the model of translation shutoff.…”

Chapter 3 Virus Versus Host Cell Translation

“…4A). PABP is targeted for cleavage by the 2Apro and 3Cpro of Poliovirus and CVB-3 (Joachims et al, 1999;Kerekatte et al, 1999;Kuyumcu-Martinez et al, 2002, 2004b, by L-pro of FMDV (Rodríguez Pulido et al, 2007), and by 3Cpro of HAV . PABP is proteolytically processed by the calicivirus 3C-like protease (Kuyumcu-Martinez et al, 2004a), and HIV-1 and HIV-2 proteases are also able to cleave PABP in the absence of other viral proteins (Alvarez et al, 2006).…”