Quantitative SUMO-1 Modification of a Vaccinia Virus Protein Is Required for Its Specific Localization and Prevents Its Self-Association

European Molecular Biology Laboratory, Cell Biology and Biophysics Programme, 69117 Heidelberg, Germany.
Molecular Biology of the Cell (Impact Factor: 4.47). 07/2005; 16(6):2822-35. DOI: 10.1091/mbc.E04-11-1005
Source: PubMed


Vaccinia virus (VV), the prototype member of the Poxviridae, a family of large DNA viruses, carries out DNA replication in specialized cytoplasmic sites that are enclosed by the rough endoplasmic reticulum (ER). We show that the VV gene product of A40R is quantitatively modified by SUMO-1, which is required for its localization to the ER-enclosed replication sites. Expression of A40R lacking SUMO-1 induced the formation of rod-shaped cytoplasmic aggregates. The latter likely consisted of polymers of nonsumoylated protein, because unmodified A40R interacted with itself, but not with the SUMO-1-conjugated protein. Using a bacterial sumoylation system, we furthermore show that unmodified A40R is mostly insoluble, whereas the modified form is completely soluble. By electron microscopy, the A40R rods seen in cells were associated with the cytosolic side of the ER and induced the apposition of several ER cisternae. A40R is the first example of a poxvirus protein to acquire SUMO-1. Its quantitative SUMO-1 modification is required for its proper localization to the viral "mini-nuclei" and prevents its self-association. The ability of the nonsumoylated A40R to bring ER membranes close together could suggest a role in the fusion of ER cisternae when these coalesce to enclose the VV replication sites.

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Available from: Katarzyna Chmielarska Masoumi, Aug 25, 2015
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    • "This posttranslational modification of proteins with SUMO (sumoylation) is involved in a variety of different cellular pathways, often by regulating protein–protein or protein–DNA interactions (Johnson, 2004; Hay, 2005; Geiss-Friedlander and Melchior, 2007; Wilkinson and Henley, 2010). More recently, increasing evidence suggests that SUMO may also contribute to protein solubility (Palacios et al., 2005; Fei et al., 2006; Mukherjee et al., 2009; Janer et al., 2010). A common feature of sporadic forms of neurodegenerative disease is a decreased solubility of specific disease-associated proteins and, concomitantly, an enhanced pathological propensity to form aggregates. "
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    • "Studies have revealed that the capsid and envelope proteins of several viruses could either interact with SUMO or Ubc9 (the SUMO E2 ligation enzyme) or were SUMO modified during virus infection; these viruses including the Tula hantavirus, Epstein-Barr virus, cyto-Megalo virus, Dengue virus, herpes virus and Molony murine leukemia virus [11-14]. Moreover, quantitative SUMO modification of a vaccinia virus protein A40R prevents A40R proteins from self-polymerization and aggregation in vivo [15]. We postulated that SUMO modification might be a common mechanism for virus proteins to retain their solubility or to prevent improper aggregation before virus assembly [9]. "
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