In this study, we reported that small glutamine-rich TPR-containing protein (SGT) interacted with not only Hsp90 alpha but also Hsp90 beta. Confocal analysis showed that treatment of cells with Hsp90-specific inhibitor geldanamycin (GA) disrupted the interaction of SGT with Hsp90 beta and this contributed to the increase of nuclear localization of SGT in HeLa cells. The increased nuclear localization of SGT was further confirmed by the Western blotting in GA-treated HeLa cells and H1299 cells. In our previous study, SGT was found to be a new pro-apoptotic factor, so we wondered whether the sub-cellular localization of SGT was related with cell apoptosis. By confocal analysis we found that the nuclear import of SGT was significantly increased in STS-induced apoptotic HeLa cells, which implied that the subcellular localization of SGT was closely associated with Hsp90 beta and apoptosis. (c) 2006 Elsevier Inc. All rights reserved.