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Cell Microbiol. 2013 Feb;15(2):213-26. doi: 10.1111/cmi.12041. Epub 2012 Nov 6.

ESCRT-III CHMP2A and CHMP3 form variable helical polymers in vitro and act synergistically during HIV-1 budding.

Author information

1
Unit of Virus Host Cell Interactions, UMI 3265, Université Joseph Fourier-EMBL-CNRS, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France.

Abstract

The endosomal sorting complex required for transport-III (ESCRT-III) proteins are essential for budding of some enveloped viruses, for the formation of intraluminal vesicles at the endosome and for the abscission step of cytokinesis. ESCRT-III proteins form polymers that constrict membrane tubes, leading to fission. We have used electron cryomicroscopy to determine the molecular organization of pleiomorphic ESCRT-III CHMP2A-CHMP3 polymers. The three-dimensional reconstruction at 22 Å resolution reveals a helical organization of filaments of CHMP molecules organized in a head-to-tail fashion. Protease susceptibility experiments indicate that polymerization is achieved via conformational changes that increase the protomer stability. Combinatorial siRNA knockdown experiments indicate that CHMP3 contributes synergistically to HIV-1 budding, and the CHMP3 contribution is ~ 10-fold more pronounced in concert with CHMP2A than with CHMP2B. This is consistent with surface plasmon resonance affinity measurements that suggest sequential CHMP4B-CHMP3-CHMP2A recruitment while showing that both CHMP2A and CHMP2B interact with CHMP4B, in agreement with their redundant functions in HIV-1 budding. Our data thus indicate that the CHMP2A-CHMP3 polymer observed in vitro contributes to HIV-1 budding by assembling on CHMP4B polymers.

PMID:
23051622
PMCID:
PMC3783020
DOI:
10.1111/cmi.12041
[Indexed for MEDLINE]
Free PMC Article

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