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Journal of Virology, January 1999, p. 709-717, 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 Coxsackievirus 2A Protease In Vitro and In Vivo: Another Mechanism for Host Protein Synthesis Shutoff?

Vaishali Kerekatte,1 Brett D. Keiper,1 Cornel Badorff,2 Aili Cai,1 Kirk U. Knowlton,2 and Robert E. Rhoads1,*

Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, Shreveport, Louisiana 71130,1 and Department of Medicine, University of California, San Diego, California 921032

Received 24 August 1998/Accepted 25 September 1998

Infection of cells by picornaviruses of the rhinovirus, aphthovirus, and enterovirus groups results in the shutoff of host protein synthesis but allows viral protein synthesis to proceed. Although considerable evidence suggests that this shutoff is mediated by the cleavage of eukaryotic translation initiation factor eIF4G by sequence-specific viral proteases (2A protease in the case of coxsackievirus), several experimental observations are at variance with this view. Thus, the cleavage of other cellular proteins could contribute to the shutoff of host protein synthesis and stimulation of viral protein synthesis. Recent evidence indicates that the highly conserved 70-kDa cytoplasmic poly(A)-binding protein (PABP) participates directly in translation initiation. We have now found that PABP is also proteolytically cleaved during coxsackievirus infection of HeLa cells. The cleavage of PABP correlated better over time with the host translational shutoff and onset of viral protein synthesis than did the cleavage of eIF4G. In vitro experiments with purified rabbit PABP and recombinant human PABP as well as in vivo experiments with Xenopus oocytes and recombinant Xenopus PABP demonstrate that the cleavage is catalyzed by 2A protease directly. N- and C-terminal sequencing indicates that cleavage occurs uniquely in human PABP at 482VANTSTQTMdown-arrow GPRPAAAAAA500, separating the four N-terminal RNA recognition motifs (80%) from the C-terminal homodimerization domain (20%). The N-terminal cleavage product of PABP is less efficient than full-length PABP in restoring translation to a PABP-dependent rabbit reticulocyte lysate translation system. These results suggest that the cleavage of PABP may be another mechanism by which picornaviruses alter the rate and spectrum of protein synthesis.

* Corresponding author. Mailing address: Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, 1501 Kings Highway, Shreveport, LA 71130-3932. Phone: (318) 675-5161. Fax: (318) 675-5180. E-mail: rrhoad{at}lsumc.edu.

Journal of Virology, January 1999, p. 709-717, Vol. 73, No. 1
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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