Interaction between HSP70 homolog and filamentous virions of the beet yellows virus

An HSP70 homolog (HSP70h), encoded by the Closterovirus Beet yellows virus (BYV), functions in viral movement from cell to cell. A previous study revealed that in infected cells, HSP70h colocalizes with the masses of BW filamentous virions. Here we demonstrate that HSP70h forms a physical complex with BW virions. This conclusion is based on both the comigration of HSP70h with BW virions in sucrose density gradients a nd the coimmunoprecipitation of the HS P70h and BW capsid protein using anti-HSP70h serum. The HSP70h-virion complex is stable at high concentrations of sodium chloride; its dissociation using sodium dodecyl sulfate, lithium chloride, or alkaline pH was accompanied by virion disassembly. However, the complex formation does not involve covalent bonds between HSP70h and Virion components. Each BW virion contains approximately 10 molecules of HSP70h. The possible role of HSP70h interaction with the virions in cell-to-cell movement of BYV is discussed, (C) 2000 Academic Press.