Novel virus-inducible stress protein required for rhabdovirus growth

Virus-inducible stress protein (VISP) is novel stress protein induced by infection of a fish rhabdovirus. In this paper, we present the molecular cloning and characterization of a gene encoding this protein named virus-inducible stress protein (VISP). A cDNA of 2193-bp open reading frame encoding the VISP with 730 amino acid residues (Mr 79.84) was cloned. While the nucleotide sequence of VISP shows no similarity with other genes in the GenBank, the amino acid sequence of the VISP has similarity with the bacterial extracellular solute-binding protein family 5 (SBP_bac_5) that is proposed to have chaperone activity. Recombinant VISP expressed in E. coli promoted the functional folding of aglucosidase after urea denaturation and also prevented thermal aggregation of alcohol dehydrogenase. Suppression of the expression of the VISP by siRNA treatment reduced the titer of rhabdovirus extracellular infectious virions by 2 orders of magnitude without influencing cell proliferation. In conclusion, we cloned a novel stress protein, VISP and found that VISP is important for the rhabdovirus growth in cultured cells.