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Functional Replacement of a Retroviral Late Domain by Ubiquitin Fusion
Author(s) -
Joshi Anjali,
Munshi Utpal,
Ablan Sherimay D.,
Nagashima Kunio,
Freed Eric O.
Publication year - 2008
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2008.00817.x
Subject(s) - tsg101 , ubiquitin , biology , escrt , endosome , group specific antigen , microbiology and biotechnology , fusion protein , murine leukemia virus , vacuolar protein sorting , budding , nedd4 , virology , lipid bilayer fusion , cell fusion , virus like particle , virus , ubiquitin ligase , cell culture , genetics , gene , microvesicles , recombinant dna , microrna , intracellular
Retroviral Gag polyprotein precursors are both necessary and sufficient for the assembly and release of virus‐like particles (VLPs) from infected cells. It is well established that small Gag‐encoded motifs, known as late domains, promote particle release by interacting with components of the cellular endosomal sorting and ubiquitination machinery. The Gag proteins of a number of different retroviruses are ubiquitinated; however, the role of Gag ubiquitination in particle egress remains undefined. In this study, we investigated this question by using a panel of equine infectious anemia virus (EIAV) Gag derivatives bearing the wild‐type EIAV late domain, heterologous retroviral late domains or no late domain. Ubiquitin was fused in cis to the C‐termini of these Gag polyproteins, and the effects on VLP budding were measured. Remarkably, fusion of ubiquitin to EIAV Gag lacking a late domain (EIAV/ΔYPDL‐Ub) largely rescued VLP release. We also determined the effects of ubiquitin fusion on the sensitivity of particle release to budding inhibitors and to depletion of key endosomal sorting factors. Ubiquitin fusion rendered EIAV/ΔYPDL‐Ub sensitive to depletion of cellular endosomal sorting factors Tsg101 and Alix and to overexpression of dominant‐negative fragments of Tsg101 and Alix. These findings demonstrate that ubiquitin can functionally compensate for the absence of a retroviral late domain and provide insights into the host‐cell machinery engaged by ubiquitin during particle egress.