DUAL CYTOPLASMIC AND NUCLEAR-DISTRIBUTION OF THE NOVEL ARSENITE-STIMULATED HUMAN ATPASE (HASNA-I)

The arsenite-stimulated human ATPase (hASNA-I) protein is a distinct h uman ATPase whose cDNA was cloned by sequence homology to the Escheric hia coli ATPase arsA. Its subcellular localization in human malignant melanoma T289 cells was examined to gain insight into the role of hASN A-I in the physiology of human cells. Immunocytochemical staining usin g the specific anti-hASNA-I monoclonal antibody 5G8 showed a cytoplasm ic, perinuclear and nucleolar distribution. Subcellular fractionation indicated that the cytoplasmic hASNA-I was soluble and that the perinu clear distribution was due to association with the nuclear membrane ra ther than with the endoplasmic reticulum. its presence in the nucleolu s was confirmed by showing colocalization with an antibody of known nu cleolar specificity. Further immunocytochemical analysis showed that t he hASNA-I at the nuclear membrane was associated with invaginations i nto the nucleus in interphase cells. These results indicate that hASNA -I is a paralogue of the bacterial ArsA protein and suggest that it pl ays a role in the nucleocytoplasmic transport of a nucleolar component . (C) 1998 Wiley-Liss, Inc.