EntrezGeneSummary | HistonesarebasicnuclearproteinsthatareresponsIBLeforthenucleosomestructureofthechromosomalfiberineukaryotes.Twomoleculesofeachofthefourcorehistones(H2A,H2B,H3,andH4)formanoctamer,aroundwhichapproximately146bpofDNAiswrappedinrepeatingunits,callednucleosomes.Thelinkerhistone,H1,interactswithlinkerDNAbetweennucleosomesandfunctionsinthecompactionofchromatinintohigherorderstructures.ThisgeneencodesamemberofthehistoneH2Afamily,andgeneratestwotranscriptsthroughtheuseoftheconservedstem-loopterminationmotif,andthepolyAadditionmotif. |
UniProtSummary | FUNCTION:SwissProt:P16104#VarianthistoneH2AwhichreplacesconventionalH2Ainasubsetofnucleosomes.NucleosomeswrapandcompactDNAintochromatin,limitingDNAaccessibilitytothecellularmachinerieswhichrequireDNAasatemplate.Histonestherebyplayacentralroleintranscriptionregulation,DNArepair,DNAreplicationandchromosomalstability.DNAaccessibilityisregulatedviaacomplexsetofpost-translationalmodificationsofhistones,alsocalledhistonecode,andnucleosomeremodeling.Requiredforcheckpoint-mediatedarrestofcellcycleprogressioninresponsetolowdosesofionizingrADIationandforefficientrepairofDNAdoublestrandbreaks(DSBs)specificallywhenmodifiedbyC-terminalphosphorylation. SIZE:143aminoacids;15145Da SUBUNIT:ThenucleosomeisahistoneoctamercontainingtwomoleculeseachofH2A,H2B,H3andH4assembledinoneH3-H4heterotetramerandtwoH2A-H2Bheterodimers.Theoctamerwrapsapproximately147bpofDNA.InteractswithnumerousproteinsrequiredforDNAdamagesignalingandrepairwhenphosphorylatedonSer-140.TheseincludeMDC1,TP53BP1,BRCA1andtheMRNcomplex,composedofMRE11A,RAD50,andNBN.InteractionwiththeMRNcomplexismediatedatleastinpartbyNBN.AlsointeractswithDHX9/NDHIIwhenphosphorylatedonSer-140. SUBCELLULARLOCATION:Nucleus.DEVELOPMENTALSTAGE:SynthesizedinG1aswellasinS-phase. DOMAIN:SwissProt:P16104The[ST]-QmotifconstitutesarecognitionsequenceforkinasesfromthePI3/PI4-kinasefamily. PTM:PhosphorylatedonSer-140(toformgamma-H2AFX)inresponsetoDNAdoublestrandbreaks(DSBs)generatedbyexogenousgenotoxicagentsandbystalledreplicationforks,andmayalsooccurduringmeioticrecombinationeventsandimmunoglobulinclassswitchinginlymphocytes.PhosphorylationcanextenduptoseveralthousandnucleosomesfromtheactualsiteoftheDSBandmaymarkthesurroundingchromatinforrecruitmentofproteinsrequiredforDNAdamagesignalingandrepair.Widespreadphosphorylationmayalsoservetoamplifythedamagesignaloraidrepairofpersistentlesions.PhosphorylationofSer-140inresponsetoionizingradiationismediatedbybothATMandPRKDCwhiledefectsinDNAreplicationinduceSer-140phosphorylationsubsequenttoactivationofATRandPRKDC.DephosphorylationofSer-140byPP2AisrequiredforDNADSBrepair.Inmeiosis,Ser-140phosphorylationmayoccuratsynaptonemalcomplexesduringleptoteneasanATM-dependentresponsetotheformationofprogrammedDSBsbySPO11.Ser-140phosphorylationmaysubsequentlyoccursatunsynapsedregionsofbothautosomesandtheXYbivalentduringzygotene,downstreamofATRandBRCA1activation.Ser-140phosphorylationmayalsoberequiredfortranscriptionalrepressionofunsynapsedchromatinandmeioticsexchromosomeinactivation(MSCI),wherebytheXandYchromosomescondenseinpachytenetoformtheheterochromaticXY-body.Duringimmunoglobulinclassswitchrecombinationinlymphocytes,Ser-140phosphorylationmayoccuratsitesofDNA-recombinationsubsequenttoactivationoftheactivation-inducedcytidinedeaminaseAICDA.&MonoubiquitinationofLys-120byRING1andRNF2/RING2complexgivesaspecifictagforepigenetictranscriptionalrepression(Bysimilarity). SIMILARITY:BelongstothehistoneH2Afamily. |