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Nucleic Acids Res October 13, 2017; 45 (18): 10583-10594.
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Protein phosphatase 1 and phosphatase 1 nuclear targeting subunit-dependent regulation of DNA-dependent protein kinase and non-homologous end joining.

Zhu S , Fisher LA , Bessho T , Peng A .

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) plays a key role in mediating non-homologous end joining (NHEJ), a major repair pathway for DNA double-strand breaks (DSBs). The activation, function and dynamics of DNA-PKcs is regulated largely by its reversible phosphorylation at numerous residues, many of which are targeted by DNA-PKcs itself. Interestingly, these DNA-PKcs phosphorylation sites function in a distinct, and sometimes opposing manner, suggesting that they are differentially regulated via complex actions of both kinases and phosphatases. In this study we identified several phosphatase subunits as potential DSB-associated proteins. In particular, protein phosphatase 1 (PP1) is recruited to a DSB-mimicking substrate in Xenopus egg extracts and sites of laser microirradiation in human cells. Depletion of PP1 impairs NHEJ in both Xenopus egg extracts and human cells. PP1 binds multiple motifs of DNA-PKcs, regulates DNA-PKcs phosphorylation, and is required for DNA-PKcs activation after DNA damage. Interestingly, phosphatase 1 nuclear targeting subunit (PNUTS), an inhibitory regulator of PP1, is also recruited to DNA damage sites to promote NHEJ. PNUTS associates with the DNA-PK complex and is required for DNA-PKcs phosphorylation at Ser-2056 and Thr-2609. Thus, PNUTS and PP1 together fine-tune the dynamic phosphorylation of DNA-PKcs after DNA damage to mediate NHEJ.

PubMed ID: 28985363
PMC ID: PMC5737533
Article link: Nucleic Acids Res
Grant support: [+]

Species referenced: Xenopus
Genes referenced: atm brca1 chek1 chek2 h2ax h2axl h2bc21 mbp nbn npy4r ppp1r10 ppp6c rrad xrcc4

Article Images: [+] show captions
References [+] :
Ali, Requirement of protein phosphatase 5 in DNA-damage-induced ATM activation. 2004, Pubmed