The N-terminal half of NPM dissociates from nucleoli of HeLa cells after anticancer drug treatments

NPM (nucleophosmin/B23) is a nucleolar phosphoprotein abundant in tumor cel ls. It dissociates from nucleoli of cells after treatments with various ant icancer drugs, To determine the domain of NPM responsible for nucleolar bin ding, the N- and C-terminal halves of NPM were fused to GFP (green fluoresc ent protein) and introduced into HeLa cells. The N-terminal half (aa 1-150) of NPM (GFP-NPMN) was found localized in the nucleoli, A stable transforma nt of GFP-NPMN in HeLa cells was prepared and tested for association to nuc leoli after anticancer drug treatments. GFP-NPMN dissociates from nucleoli after treatments with daunomycin, actinomycin D, camptothecin, and toyocamy cin, The dissociation is time- and dose-dependent, and correlates with the cytotoxicity induced by the drugs. These results indicate that a stable tra nsformant of GFP-NPMN in HeLa cells may be useful for the screening of anti cancer drugs. (C) 1999 Academic Press.