Aggresomes Resemble Sites Specialized for Virus Assembly

The large cytoplasmic DNA viruses such as poxviruses, iridoviruses, and African swine fever virus (ASFV) assemble in discrete perinuclear foci called viral factories. Factories exclude host proteins, suggesting that they are novel subcellular structures induced by viruses. Novel perinuclear structures, called aggresomes are also formed by cells in response to misfolded protein (Johnston, J.A., C.L. Ward, and R.R. Kopito. 1998. J. Cell Biol. 143:1883--1898; García-Mata, R., Z. Bebök, E.J. Sorscher, and E.S. Sztul. 1999. J. Cell Biol. 146:1239--1254). In this study, we have investigated whether aggresomes and viral factories are related structures. Aggresomes were compared with viral factories produced by ASFV. Aggresomes and viral factories were located close to the microtubule organizing center and required an intact microtubular network for assembly. Both structures caused rearrangement of intermediate filaments and the collapse of vimentin into characteristic cages, and both recruited mitochondria and cellular chaperones. Given that ASFV factories resemble aggresomes, it is possible that a cellular response originally designed to reduce the toxicity of misfolded proteins is exploited by cytoplasmic DNA viruses to concentrate structural proteins at virus assembly sites.