Publication Date:
2014-05-21
Description:
The protein kinase activity of the DNA dependent protein kinase catalytic subunit (DNA-PKcs) and its autophosphorylation are critical for DNA double strand break repair via non-homologous end-joining (NHEJ). Recent studies have shown that depletion or inactivation of DNA-PKcs kinase activity also results in mitotic defects. DNA-PKcs is autophosphorylated on Ser-2056, Thr-2647 and Thr-2609 in mitosis and phosphorylated DNA-PKcs localize to centrosomes, mitotic spindles and the midbody. DNA-PKcs also interacts with protein phosphatase 6 (PP6), and PP6 has been shown to dephosphorylate Aurora A kinase in mitosis. Here, we report that DNA-PKcs is phosphorylated on Ser-3205 and Thr-3950 in mitosis. Phosphorylation of Thr-3950 is DNA-PK-dependent whereas phosphorylation of Ser-3205 requires polo-like kinase 1 (PLK1). Moreover, PLK1 phosphorylates DNA-PKcs on Ser-3205 in vitro and interacts with DNA-PKcs in mitosis. In addition, PP6 dephosphorylates DNA-PKcs at Ser-3205 in mitosis and after IR. DNA-PKcs also phosphorylates Chk2 on Thr-68 in mitosis and both phosphorylation of Chk2 and autophosphorylation of DNA-PKcs in mitosis occur in the apparent absence of Ku and DNA damage. Our findings provide mechanistic insight into the roles of DNA-PKcs and PP6 in mitosis and suggest that DNA-PKcs’ role in mitosis may be mechanistically distinct from its well-established role in NHEJ.
Print ISSN:
0144-8463
Electronic ISSN:
1573-4935
Topics:
Biology
,
Chemistry and Pharmacology
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