The outcomes are expressed as the percentage of cells displaying Bax or Bak NT exposure compared with those cells showing H1 or NPM redistribution or the percentage of cells showing H1 or NPM redistribution compared with those showing Bax or Bak NT exposure. The values are represented as means S. E. M.. MEFs, mouse embryonic fibroblasts, NPM, nucleophosmin, NT, N terminal, WT, wild type Figure 7 Bcl xL over-expression Aurora B inhibitor does not prevent stress induced NPM, H1 and nucleolin re-distribution. Bcl xL cells and empty vector secure transfectants untreated or treated for 24 h with 25 mM cisplatin were double stained with anti NPM or anti H1 together with anti Bcl xL antibodies, or with anti nucleolin together with anti FLAG antibodies, and with Hoechst 33258, after which they were visualized by fluorescence microscopy. The pictures of each treatment represent exactly the same industry visualized individually for detecting antibody staining and Hoechst stained nuclei. The results presented are from a representative experiment. Arrows indicate cells and their nuclei that show nuclear protein re-distribution. Bars, 20 Immune system mm. H1, histone 1, NPM, nucleophosmin We focused on the re-distribution of three nuclear meats, particularly, H1, NPM and nucleolin in response to four different apoptotic stimuli. In all cases, we detected a redistribution of these proteins. This effect was seen early after inducing apoptosis. Like, significant nuclear protein redistribution was evident at 9 h after cisplatin or camptothecin treatment, when phosphatidylserine translocation, Bax/Bak NT exposure, cytochrome c or caspase 3 activation hadn’t yet been detected. These findings explain why the redistribution effect was GW0742 independent of the Apaf 1/caspase 9 apoptosome and of caspases generally, as these components are known to be activated later. Jointly, our results suggest that the re-distribution effect occurs upstream or independently of the mitochondrial pathway. Not all nuclear proteins display nuclear protein redistribution. As an example, KAP 1 did not change its nuclear localization underneath the same conditions. This suggests that the redistribution effect was specific for a particular class of nuclear proteins that share a yet unknown property. As the redistribution precedes the appearance of apoptotic functions and did not affect all nuclear proteins, it can’t be due to a normal leakage from destroyed nuclei. It was formerly proposed that cytosolic H1. Apoptosis is facilitated by and NPM through Bax/Bak. Our finding that the H1 and NPM re-distribution is mediated through Bax/Bak implies that Bax and Bak act upstream of H1. and NPM, and ergo determine the ability of those nuclear proteins to activate them. In the molecular genetic level, these types of conditions are characterized by very well defined, specific non random abnormalities that are potential targets for new therapy.