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Journal of Virology, September 2007, p. 8977-8988, Vol. 81, No. 17
0022-538X/07/$08.00+0     doi:10.1128/JVI.00657-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Basic Residues in the Mason-Pfizer Monkey Virus Gag Matrix Domain Regulate Intracellular Trafficking and Capsid-Membrane Interactions{triangledown}

Elizabeth Stansell,1,{dagger} Robert Apkarian,2,{ddagger} Sarka Haubova,3 William E. Diehl,1 Ewan M. Tytler,4 and Eric Hunter1*

Department of Pathology and Emory Vaccine Center at Yerkes Regional Primate Research Center,1 Integrated Microscopy and Microanalytical Facility, Emory University, Atlanta, Georgia 30329,2 Department of Biochemistry and Microbiology, Institute of Chemical Technology, Technicka 3, 166 28 Prague, Czech Republic,3 Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama 352944

Received 27 March 2007/ Accepted 18 June 2007

Mason-Pfizer monkey virus (M-PMV) capsids that have assembled in the cytoplasm must be transported to and associate with the plasma membrane prior to being enveloped by a lipid bilayer during viral release. Structural studies have identified a positive-charge density on the membrane-proximal surface of the matrix (MA) protein component of the Gag polyprotein. To investigate if basic amino acids in MA play a role in intracellular transport and capsid-membrane interactions, mutants were constructed in which lysine and arginine residues (R10, K16, K20, R22, K25, K27, K33, and K39) potentially exposed on the capsid surface were replaced singly and in pairs by alanine. A majority of the charge substitution mutants were released less efficiently than the wild type. Electron microscopy of mutant Gag-expressing cells revealed four distinct phenotypes: K16A and K20A immature capsids accumulated on and budded into intracellular vesicles; R10A, K27A, and R22A capsid transport was arrested at the cellular cortical actin network, while K25A immature capsids were dispersed throughout the cytoplasm and appeared to be defective at an earlier stage of intracellular transport; and the remaining mutant (K33A and K39A) capsids accumulated at the inner surface of the plasma membrane. All mutants that released virions exhibited near-wild-type infectivity in a single-round assay. Thus, basic amino acids in the M-PMV MA define both cellular location and efficiency of virus release.

* Corresponding author. Mailing address: Emory University Vaccine Center, 934 Gatewood Rd. NE, Rm. 1026, Atlanta, GA 30329. Phone: (404) 727-8587. Fax: (404) 727-5631. E-mail: eric.hunter2{at}emory.edu

{triangledown} Published ahead of print on 27 June 2007.

{dagger} Present address: New England Primate Research Center, Harvard Medical School, One Pine Hill Drive, Southborough, MA 01772.

{ddagger} Deceased.

Journal of Virology, September 2007, p. 8977-8988, Vol. 81, No. 17
0022-538X/07/$08.00+0     doi:10.1128/JVI.00657-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Diehl, W. E., Stansell, E., Kaiser, S. M., Emerman, M., Hunter, E. (2008). Identification of Postentry Restrictions to Mason-Pfizer Monkey Virus Infection in New World Monkey Cells. J. Virol. 82: 11140-11151 [Abstract] [Full Text]  


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