Assessment of the subcellular localization of the herpes simplex virus structural protein VP22 in the absence of other viral gene products

We previously demonstrated that the herpes simplex virus type 1 (HSV-1) str uctural protein VP22 exists in the cytoplasm early in infection and migrate s to and accumulates in the nucleus late in infection (J. Virol. 73(8) (199 9) 6769). The goal of this study is to document the behavior of VP22 in cel ls in the absence of other viral polypeptides. We characterized the effects of various indirect immunofluorescence sample preparation conditions on th e localization of VP22 in cells and have determined the following. (i) Fixi ng with formaldehyde and permeabilizing with acetone maintains the structur e of microtubules in cells, in as much as we observed classic microtubule o rganizing centers. (ii) Acetone or methanol alone did not completely fix th e cells. (iii) Triton X-100 decreased tubulin immunofluorescence signals in our system. (iv) VP22 predominated in the nucleus of cells that were fixed with formaldehyde. Based on our results, we conclude the following. (v) Du e to the partial fixation by acetone or methanol alone, microtubules form d iffuse irregular shapes. (vi) VP22 is detected in the cytoplasm of cells fi xed with acetone or methanol only due to its seepage from the nucleus. Take n together, these findings indicate that (vii) the nuclear localization of VP22 does not require additional viral factors. (C) 2001 Elsevier Science B .V. All rights reserved.