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Journal of Virology, January 1999, p. 718-727, Vol. 73, No. 1
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

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

Michelle Joachims, Pieter C. Van Breugel,dagger and Richard E. Lloyd*

Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104

Received 11 June 1998/Accepted 11 October 1998

Many enteroviruses, members of the family Picornaviridae, 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.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104. Phone: (405) 271-2889. Fax: (405) 271-5440. E-mail: richard-lloyd{at}ouhsc.edu.

dagger Present address: Department of Molecular Cell Biology, University of Utrecht, 3584 CH Utrecht, The Netherlands.

Journal of Virology, January 1999, p. 718-727, Vol. 73, No. 1
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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