Biphasic translocation of a 70 kDa heat shock protein in human cytomegalovirus-infected cells.

Human cytomegalovirus (HCMV) reportedly induces the expression of a 70 kDa heat shock protein (hsp70) with no known function in the virus replication cycle. We report here a remarkably specific translocation pattern of hsp70 during HCMV infection of human diploid fibroblasts. Immunofluorescent observation and Western blotting of subcellular fractions revealed nuclear localization of hsp70 early in infection and predominantly cytoplasmic localization of hsp70 late in infection. Treatment of HCMV-infected cells with cycloheximide followed by treatment with actinomycin D allowed virus immediate-early gene expression but inhibited hsp70 nuclear localization. Phosphonoacetic acid and tunicamycin, both of which reportedly inhibit HCMV DNA replication, did not inhibit HCMV-induced nuclear localization of hsp70 but inhibited hsp70 translocation from the nucleus to the cytoplasm. These results indicate a correlation between HCMV multiplication and hsp70 localization, suggesting that hsp70 may play a role in HCMV multiplication.