Cell-cycle-dependent nuclear translocation of HSP70 in amphibian embryonic cells.

Using immunocytochemical methods, we analyzed the localization of the HSP70 protein constitutively expressed during embryogenesis in the amphibian Pleurodeles waltl. Our results provide evidence for nuclear transfer of the protein during gastrulation, and particularly for predominant nuclear labeling in gastrula internalized cells. Using two inhibitors of DNA replication -hydroxyurea (HUA) and aphidicolin- or/and an inhibitor of transcription -actinomycin D- applied to embryos, we demonstrated that nuclear transfer of HSP70 is related to the transcriptional activity of the cells during the early S phase of the cell cycle.