Tracking and Elucidating Alphavirus-Host Protein Interactions

doi:10.1074/jbc.M603980200

Tracking and Elucidating Alphavirus-Host Protein Interactions^*

^{^‡}Mass Spectrometry and Gaseous Ion Chemistry, ^{^§}Virology and Infectious Disease, and ^{^¶}Cellular and Structural Biology, The Rockefeller University, New York, New York 10021

1 To whom correspondence may be addressed: The Rockefeller University, 1230 York Ave., New York, NY 10021. Tel.: 212-327-8849; Fax: 212-327-7547; E-mail: chait{at}rockefeller.edu.
2 To whom correspondence may be addressed: The Rockefeller University, 1230 York Ave., New York, NY 10021. Tel.: 212-327-7078; Fax: 212-327-7048; E-mail: macdonm{at}rockefeller.edu.

Abstract

Viral infections cause profound alterations in host cells. Here, we explore the interactions between proteins of the Alphavirus Sindbis and host factors during the course of mammalian cell infection. Using a mutant virus expressing the viral nsP3 protein tagged with green fluorescent protein (GFP) we directly observed nsP3 localization and isolated nsP3-interacting proteins at various times after infection. These results revealed that host factor recruitment to nsP3-containing complexes was time dependent, with a specific early and persistent recruitment of G3BP and a later recruitment of 14-3-3 proteins. Expression of GFP-tagged G3BP allowed reciprocal isolation of nsP3 in Sindbis infected cells, as well as the identification of novel G3BP-interacting proteins in both uninfected and infected cells. Note-worthy interactions include nuclear pore complex components whose interactions with G3BP were reduced upon Sindbis infection. This suggests that G3BP is a nuclear transport factor, as hypothesized previously, and that viral infection may alter RNA transport. Immunoelectron microscopy showed that a portion of Sindbis nsP3 is localized at the nuclear envelope, suggesting a possible site of G3BP recruitment to nsP3-containing complexes. Our results demonstrate the utility of using a standard GFP tag to both track viral protein localization and elucidate specific viral-host interactions over time in infected mammalian cells.

Footnotes

↵3 The abbreviations used are: nsP, nonstructural protein; GFP, green fluorescent protein; mRFP, monomeric red fluorescent protein; G3BP, Ras-GTPase-activating protein SH3-domain-binding protein; m.o.i., multiplicity of infection; 14-3-3, tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein; hnRNP, heterogeneous nuclear ribonucleoproteins; NTF, nuclear transport factor; TIA, T-cell intracellular antigen; MS, mass spectrometry; MS/MS, tandem MS; EM, electron microscopy; PBS, phosphate-buffered saline; RRM, RNA recognition motif; MALDI, matrix-assisted laser desorption ionization; TTP, tristetraprolin.
↵4 M. V. Soukhodolets and C. M. Rice, unpublished data.
↵^* This work was supported by National Institutes of Health Grants AI063233 (to M. R. M.), AI24134 (to C. M. R.), RR00862 (to B. T. C.), RR022220 (to M. P. R. and B. T. C.), and GM062427 (to M. P. R.); by The Rockefeller University Women and Science Fellowship CEN5300379 (to I. M. C.); and by the Greenberg Medical Research Institute. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵ The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. S11-S14 and Tables S1 and S2.
- Received April 26, 2006.
- Revision received July 10, 2006.