Seeonlineversionforlegendandreferences.646Cell142,August20,2010©2010ElsevierInc.DOI10.1016/j.cell.2010.08.006SnapShot:HomologousRecombinationinDNADouble-StrandBreakRepairGerardMazón,EleniP.Mimitou,andLorraineS.SymingtonDepartmentofMicrobiologyandImmunology,ColumbiaUniversityMedicalCenter,NewYork,NY10032,USASeeonlineversionforlegendandreferences.142,August20,2010©2010ElsevierInc.DOI10.1016/j.cell.2010.08.006GerardMazón,EleniP.Mimitou,andLorraineS.SymingtonDepartmentofMicrobiologyandImmunology,ColumbiaUniversityMedicalCenter,NewYork,NY10032,USASnapShot:HomologousRecombinationinDNADouble-StrandBreakRepairGerardMazón,EleniP.Mimitou,andLorraineS.SymingtonDepartmentofMicrobiologyandImmunology,ColumbiaUniversityMedicalCenter,NewYork,NY10032,USA646.e1Cell142,August20,2010©2010ElsevierInc.DOI10.1016/j.cell.2010.08.006Homologousrecombination(HR)providesanimportantmechanismtorepairbothaccidentalandprogrammedDNAdouble-strandbreaks(DSBs)duringmitosisandmeiosis.DefectsinHRareassociatedwithmutagenesisandpredisposetocancer,highlightingtheimportanceofthispathwayforpreservinggenomeintegrity(MoynahanandJasin,2010).HRisactiveintheSandG2phasesofthecellcyclewhereitpromotesrepairofabrokenchromatidfromanintactsisterchromatid,ensuringerror-freerepair.TheDNAtransactionsassociatedwithHRareaccompaniedbymodificationstohistones,mostnotablyphosphorylationofH2A/H2AXandchromatinremodeling.ThisSnapShotshowstheyeastproteinsdirectlyinvolvedinmitoticDSBrepair;theirmammaliancounterpartsareshownontheright.ThecentralreactioninhomologousrecombinationisthepairingandexchangeofstrandsbetweentwohomologousDNAmolecules.ThisstepiscatalyzedbytheconservedRad51/RecAfamilyofproteins(Chenetal.,2008;SanFilippoetal.,2008).TogeneratethesubstrateforbindingofRad51,DNAendsareprocessedtoyield3′single-strandedDNAtails(5′–3′resection).Endresectionoccursthroughabiphasicmechanism:first,theMre11-Rad50-Xrs2(MRX)complexandSae2clip50–100nucleotidesfromthe5′endsofDNA,andthenExo1orSgs1-Top3-Rmi1andDna2processtheearlyint...
