MHV-A59 Gene 1 Proteins are Associated with Two Distinct Membrane Populations
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All of the stages of Coronavirus replication that have been investigated have been shown to occur on or within intracellular membranes. We and others have shown that mouse hepatitis virus (MHV) RNA synthesis occurs in association with intracellular membranes (Bi et al., 1998; Denison et al., 1999; Dennis and Brian, 1982; Sethna and Brian, 1997; Shi et al., 1999; van der Meer et al., 1999). Several proteins processed from the gene 1 (replicase gene) polyprotein have been shown by immunofluorescence and electron microscopic approaches to be associated with intracellular membranes. Specifically, membranes containing markers for late endosomes have been shown to be sites of localization of newly synthesized viral RNA as well as at least one of the mature gene 1 proteins (van der Meer et al., 1999). However, different patterns of gene 1 protein localization and interaction have been reported in the settings of distinct cell types, experimental approaches and virus strains. Most recently, it has been shown by confocal microscopic analysis of MHV-A59 infected cells that multiple replicase gene proteins as well as structural proteins may not completely colocalize but rather are organized in closely associated or “interdigitated” membranes, suggesting that proteins involved in MHV RNA synthesis may be localized to more than one membrane population (Bost et al., 2000).
KeywordsLate Endosome Intracellular Membrane Gradient Fraction Mouse Hepatitis Virus Replicase Gene
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