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(PP339) DNA-PK phosphorylates hstone H2AX during staurosporine-induced apoptosis of rodent cells.
Mukherjee, Bipasha*,1, Chen, Benjamin1, Kobayashi, Junya2, Chatterjee, Aloke 3, Chen, David1, Burma, Sandeep1, 1 Dept. of Radiation Oncology, Dallas, TX2 Department of Radiation Biology, Hiroshima, N/A, Japan3 Life Sciences Division, Berkeley, CA
ABSTRACT- The phosphorylation of histone H2AX at serine 139 is one of the earliest responses of mammalian cells to DNA double-strand breaks (DSBs). We have previously shown that ATM is primarily responsible for H2AX phosphorylation in murine cells in response to radiation-induced DSBs. H2AX is also phosphorylated during apoptosis concurrently with the initiation of DNA fragmentation. The kinase responsible for H2AX phosphorylation during programmed cell death (PCD) is yet to be identified. We demonstrate here that a different kinase, DNA-PK, is responsible for H2AX phosphorylation during staurosporine-induced PCD in mouse fibroblasts and Chinese hamster ovary cells. The kinase activity of DNA-PK is specifically required for H2AX phosphorylation during apoptosis. We further show that DNA-PK is activated in apoptotic cells, as evidenced by autophosphorylation of its catalytic subunit, before it is inactivated by cleavage. Moreover, DNA-PK directly phosphorylates H2AX in vitro and promotes the survival of staurosporine-treated cells. Our results clearly indicate that ATM and DNA-PK play different roles in DNA damage-induced H2AX phosphorylation in normal versus apoptotic cells.
Key words: DNA-PK, histone H2AX, apoptosis, DNA repair
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