Post-translational modification and mitochondrial relocalization of histone H3 during apoptosis induced by staurosporine.

Post-translational modifications (PTMs) of histones such as phosphorylation, acetylation, and ubiquitination, collectively referred to as the "histone-code", have been known to regulate gene expression and chromatin condensation for over a decade. They are also implicated in processes such as DNA repair and apoptosis. However, the study of the phosphorylation of histones has been mainly focused on chromosome condensation and mitosis. Therefore, the phosphorylation of histones in apoptosis is not fully understood. It was recently demonstrated by Tang et al. that histones are released from nucleosome during apoptosis, an observation that is in agreement with our findings. In addition to the release of histones, the dephosphorylation of histone H3 at Thr-3 and Ser-10 was observed during apoptosis in some cancer cells. Our data suggest that the modification and release of histones could serve markers of apoptosis in human cancer cells. We also suggest that the released histones, especially H3, could be translocated to mitochondria during apoptosis.