TRANSLOCATION OF NUCLEOPHOSMIN FROM NUCLEOLI TO NUCLEOPLASM REQUIRES ATP

The movement of nucleophosmin from nucleoli to nucleoplasm in HeLa cel ls induced by cytotoxic drugs and detected by immunofluorescence is in hibited by concomitant treatment with antimycin A in glucose-free medi um. Incubation of HeLa cells with antimycin A (300 nM; 30 min) and glu cose-free medium resulted in an approximately 90% decrease in cellular ATP pools. To study the biochemical events involved in nucleophosmin translocation, we used an in vitro system consisting of Triton-permeab ilized HeLA cells. Incubation of permeabilized cells with ATP (0.5 mM; 1 h) resulted in the translocation of nucleophosmin from nucleoli to nucleoplasm and cytoplasm. Similarly to drug-induced nucleophosmin tra nslocation in whole cultured cells, there is no reduction (measured by e.l.i.s.a.) or degradation of nucleophosmin or change in the ratio of the high-molecular-mass form to the monomeric form (ascertained by We stern blotting) during ATP treatment of permeabilized cells. Together, these results indicate a requirement for ATP for redistribution of nu cleophosmin from nucleoli to nucleoplasm. Because this permeabilized c ell model is simple and efficient and works effectively with exogenous factors, it should provide a powerful tool for investigating the bioc hemical features of nucleophosmin translocation from nucleoli to nucle oplasm.