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H2A histone family, member X
Protein H2AFX PDB 1aoi.png
PDB rendering based on 1aoi.
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols H2AFX ; H2A.X; H2A/X; H2AX
External IDs OMIM601772 MGI102688 HomoloGene134201 GeneCards: H2AFX Gene
RNA expression pattern
PBB GE H2AFX 205436 s at tn.png
PBB GE DPAGT1 212525 s at tn.png
More reference expression data
Species Human Mouse
Entrez 3014 15270
Ensembl ENSG00000188486 ENSMUSG00000049932
UniProt P16104 P27661
RefSeq (mRNA) NM_002105 NM_010436
RefSeq (protein) NP_002096 NP_034566
Location (UCSC) Chr 11:
119.09 – 119.1 Mb
Chr 9:
44.33 – 44.34 Mb
PubMed search [1] [2]

H2AFX (H2A histone family, member X) is one of several genes coding for histone H2A. In humans and other eukaryotes, the DNA is wrapped around histone-groups, consisting of core histones H2A, H2B, H3 and H4. Thus, the H2AX contributes to the nucleosome-formation and therefore the structure of DNA.

H2AX becomes phosphorylated on serine 139, then called gamma-H2AX, as a reaction on DNA Double-strand breaks (DSB). The kinases of the PI3-family (Ataxia telangiectasia mutated, ATR and DNA-PKcs) are responsible for this phosphorylation, especially ATM. The modification can happen accidentally during replication fork collapse or in the response to ionizing radiation but also during controlled physiological processes such as V(D)J recombination. Gamma-H2AX is a sensitive target for looking at DSBs in cells. The role of the phosphorylated form of the histone in DNA repair is under discussion but it is known that because of the modification the DNA becomes less condensed, potentially allowing space for the recruitment of proteins necessary during repair of DSBs. Mutagenesis experiments have shown that the modification is necessary for the proper formation of ionizing radiation induced foci in response to double strand breaks, but is not required for the recruitment of proteins to the site of DSBs.


H2AX has been shown to interact with MDC1,[1][2] Nibrin,[3] TP53BP1,[4][5][6] Bloom syndrome protein,[4] BRCA1[7][8][9] and BARD1.[7][9]


  1. ^ Stewart, Grant S; Wang Bin; Bignell Colin R; Taylor A Malcolm R; Elledge Stephen J (Feb 2003). "MDC1 is a mediator of the mammalian DNA damage checkpoint". Nature (England) 421 (6926): 961–6. doi:10.1038/nature01446. ISSN 0028-0836. PMID 12607005. 
  2. ^ Xu, Xingzhi; Stern David F (Oct 2003). "NFBD1/MDC1 regulates ionizing radiation-induced focus formation by DNA checkpoint signaling and repair factors". FASEB J. (United States) 17 (13): 1842–8. doi:10.1096/fj.03-0310com. PMID 14519663. 
  3. ^ Kobayashi, Junya; Tauchi Hiroshi; Sakamoto Shuichi; Nakamura Asako; Morishima Ken-ichi; Matsuura Shinya; Kobayashi Toshiko; Tamai Katsuyuki; Tanimoto Keiji; Komatsu Kenshi (Oct 2002). "NBS1 localizes to gamma-H2AX foci through interaction with the FHA/BRCT domain". Curr. Biol. (England) 12 (21): 1846–51. doi:10.1016/S0960-9822(02)01259-9. ISSN 0960-9822. PMID 12419185. 
  4. ^ a b Sengupta, Sagar; Robles Ana I, Linke Steven P, Sinogeeva Natasha I, Zhang Ran, Pedeux Remy, Ward Irene M, Celeste Arkady, Nussenzweig André, Chen Junjie, Halazonetis Thanos D, Harris Curtis C (Sep 2004). "Functional interaction between BLM helicase and 53BP1 in a Chk1-mediated pathway during S-phase arrest". J. Cell Biol. (United States) 166 (6): 801–13. doi:10.1083/jcb.200405128. ISSN 0021-9525. PMC 2172115. PMID 15364958. 
  5. ^ Fernandez-Capetillo, Oscar; Chen Hua-Tang, Celeste Arkady, Ward Irene, Romanienko Peter J, Morales Julio C, Naka Kazuhito, Xia Zhenfang, Camerini-Otero R Daniel, Motoyama Noboru, Carpenter Phillip B, Bonner William M, Chen Junjie, Nussenzweig André (Dec 2002). "DNA damage-induced G2-M checkpoint activation by histone H2AX and 53BP1". Nat. Cell Biol. (England) 4 (12): 993–7. doi:10.1038/ncb884. ISSN 1465-7392. PMID 12447390. 
  6. ^ Ward, Irene M; Minn Kay; Jorda Katherine G; Chen Junjie (May 2003). "Accumulation of checkpoint protein 53BP1 at DNA breaks involves its binding to phosphorylated histone H2AX". J. Biol. Chem. (United States) 278 (22): 19579–82. doi:10.1074/jbc.C300117200. ISSN 0021-9258. PMID 12697768. 
  7. ^ a b Mallery, Donna L; Vandenberg Cassandra J; Hiom Kevin (Dec 2002). "Activation of the E3 ligase function of the BRCA1/BARD1 complex by polyubiquitin chains". EMBO J. (England) 21 (24): 6755–62. doi:10.1093/emboj/cdf691. ISSN 0261-4189. PMC 139111. PMID 12485996. 
  8. ^ Paull, T T; Rogakou E P; Yamazaki V; Kirchgessner C U; Gellert M; Bonner W M (2000). "A critical role for histone H2AX in recruitment of repair factors to nuclear foci after DNA damage". Curr. Biol. (ENGLAND) 10 (15): 886–95. doi:10.1016/S0960-9822(00)00610-2. ISSN 0960-9822. PMID 10959836. 
  9. ^ a b Chen, Angus; Kleiman Frida E; Manley James L; Ouchi Toru; Pan Zhen-Qiang (Jun 2002). "Autoubiquitination of the BRCA1*BARD1 RING ubiquitin ligase". J. Biol. Chem. (United States) 277 (24): 22085–92. doi:10.1074/jbc.M201252200. ISSN 0021-9258. PMID 11927591. 

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