Reactome: A Curated Pathway Database

Recruitment and ATM-mediated phosphorylation of repair and signaling proteins at DNA double strand breaks

Stable Identifier
Homo sapiens
Locations in the PathwayBrowser

Activated ATM phosphorylates a number of proteins involved in the DNA damage checkpoint and DNA repair (Thompson and Schild 2002, Ciccia and Elledge 2010), thereby triggering and coordinating accumulation of DNA DSB repair proteins in nuclear foci known as ionizing radiation-induced foci (IRIF). While IRIFs include chromatin regions kilobases away from the actual DSB site, this Reactome pathway represents simplified foci and events that happen proximal to the DNA DSB ends. In general, proteins localizing to the nuclear foci in response to ATM signaling are cooperatively retained at the DNA DSB site, forming a positive feedback loop and amplifying DNA damage response (Soutoglou and Misteli 2008).

Activated ATM phosphorylates the NBN (NBS1) subunit of the MRN complex (MRE11A:RAD50:NBN) (Gatei et al. 2000), as well as the nucleosome histone H2AFX (H2AX) on serine residue S139, producing gamma-H2AFX (gamma-H2AX) containing nucleosomes (Rogakou et al. 1998, Burma et al. 2001). H2AFX is phosphorylated on tyrosine 142 (Y142) under basal conditions (Xiao et al. 2009). After ATM-mediated phosphorylation of H2AFX on S139, tyrosine Y142 has to be dephosphorylated by EYA family phosphatases in order for the DNA repair to proceed and to avoid apoptosis induced by DNA DSBs (Cook et al. 2009). Gamma-H2AFX recruits MDC1 to DNA DSBs (Stucki et al. 2005). After ATM phosphorylates MDC1 (Liu et al. 2012), the MRN complex, gamma-H2AFX nucleosomes, and MDC1 serve as a core of the nuclear focus and a platform for the recruitment of other proteins involved in DNA damage signaling and repair (Lukas et al. 2004, Soutoglou and Misteli 2008).

RNF8 ubiquitin ligase binds phosphorylated MDC1 (Kolas et al. 2007) and, in cooperation with HERC2 and RNF168 (Bekker-Jensen et al. 2010, Campbell et al. 2012), ubiquitinates H2AFX (Mailand et al. 2007, Huen et al. 2007, Stewart et al. 2009, Doil et al. 2009) and histone demethylases KDM4A and KDM4B (Mallette et al. 2012).

Ubiquitinated gamma-H2AFX recruits UIMC1 (RAP80), promoting the assembly of the BRCA1-A complex at DNA DSBs. The BRCA1-A complex consists of RAP80, FAM175A (Abraxas), BRCA1:BARD1 heterodimer, BRCC3 (BRCC36), BRE (BRCC45) and BABAM1 (MERIT40, NBA1) (Wang et al. 2007, Wang and Elledge 2007)

Ubiquitin mediated degradation of KDM4A and KDM4B allows TP53BP1 (53BP1) to associate with histone H4 dimethylated on lysine K21 (H4K20Me2 mark) by WHSC1 at DNA DSB sites (Pei et al. 2011).

Once recruited to DNA DSBs, both BRCA1:BARD1 heterodimers and TP53BP1 are phosphorylated by ATM (Cortez et al. 1999, Gatei et al. 2000, Kim et al. 2006, Jowsey et al. 2007), which triggers recruitment and activation of CHEK2 (Chk2, Cds1) (Wang et al. 2002, Wilson and Stern 2008, Melchionna et al. 2000).

Depending on the cell cycle stage, BRCA1 and TP53BP1 competitively promote either homology directed repair (HDR) or nonhomologous end joining (NHEJ) of DNA DSBs. HDR through homologous recombination repair (HRR) or single strand annealing (SSA) is promoted by BRCA1 in association with RBBP8 (CtIP), while NHEJ is promoted by TP53BP1 in association with RIF1 (Escribano-Diaz et al. 2013).

Literature References
PubMed ID Title Journal Year
22373579 RNF8- and RNF168-dependent degradation of KDM4A/JMJD2A triggers 53BP1 recruitment to DNA damage sites EMBO J. 2012
10550055 Requirement of ATM-dependent phosphorylation of brca1 in the DNA damage response to double-strand breaks Science 1999
15201865 Mdc1 couples DNA double-strand break recognition by Nbs1 with its H2AX-dependent chromatin retention EMBO J. 2004
10802669 ATM-dependent phosphorylation of nibrin in response to radiation exposure Nat. Genet. 2000
21293379 MMSET regulates histone H4K20 methylation and 53BP1 accumulation at DNA damage sites Nature 2011
19203579 RNF168 binds and amplifies ubiquitin conjugates on damaged chromosomes to allow accumulation of repair proteins Cell 2009
18006705 Orchestration of the DNA-damage response by the RNF8 ubiquitin ligase Science 2007
18001825 RNF8 transduces the DNA-damage signal via histone ubiquitylation and checkpoint protein assembly Cell 2007
22589545 Molecular insights into the function of RING finger (RNF)-containing proteins hRNF8 and hRNF168 in Ubc13/Mms2-dependent ubiquitylation J. Biol. Chem. 2012
19203578 The RIDDLE syndrome protein mediates a ubiquitin-dependent signaling cascade at sites of DNA damage Cell 2009
19234442 Tyrosine dephosphorylation of H2AX modulates apoptosis and survival decisions Nature 2009
17525340 Abraxas and RAP80 form a BRCA1 protein complex required for the DNA damage response Science 2007
16651405 DNA damage-induced BARD1 phosphorylation is critical for the inhibition of messenger RNA processing by BRCA1/BARD1 complex Cancer Res. 2006
16377563 MDC1 directly binds phosphorylated histone H2AX to regulate cellular responses to DNA double-strand breaks Cell 2005
10866324 Role for ATM in DNA damage-induced phosphorylation of BRCA1 Cancer Res. 2000
18001824 RNF8 ubiquitylates histones at DNA double-strand breaks and promotes assembly of repair proteins Cell 2007
17553757 Characterisation of the sites of DNA damage-induced 53BP1 phosphorylation catalysed by ATM and ATR DNA Repair (Amst.) 2007
18483401 Activation of the cellular DNA damage response in the absence of DNA lesions Science 2008
19001859 NFBD1/MDC1, 53BP1 and BRCA1 have both redundant and unique roles in the ATM pathway Cell Cycle 2008
12364621 53BP1, a mediator of the DNA damage checkpoint. Science 2002
18077395 Ubc13/Rnf8 ubiquitin ligases control foci formation of the Rap80/Abraxas/Brca1/Brcc36 complex in response to DNA damage Proc. Natl. Acad. Sci. U.S.A. 2007
11571274 ATM phosphorylates histone H2AX in response to DNA double-strand breaks J Biol Chem 2001
9488723 DNA double-stranded breaks induce histone H2AX phosphorylation on serine 139. J Biol Chem 1998
22234877 Structural mechanism of the phosphorylation-dependent dimerization of the MDC1 forkhead-associated domain Nucleic Acids Res. 2012
23333306 A cell cycle-dependent regulatory circuit composed of 53BP1-RIF1 and BRCA1-CtIP controls DNA repair pathway choice Mol. Cell 2013
19092802 WSTF regulates the H2A.X DNA damage response via a novel tyrosine kinase activity Nature 2009
20023648 HERC2 coordinates ubiquitin-dependent assembly of DNA repair factors on damaged chromosomes Nat. Cell Biol. 2010
11025670 Threonine 68 is required for radiation-induced phosphorylation and activation of Cds1 Nat. Cell Biol. 2000
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