COMMENTOpenAccessCircularRNAsaspromisingbiomarkersincancer:detection,function,andbeyondShengliLi1andLengHan1,2*EditorialsummaryCircularRNAs(circRNAs)are3′–5′covalentlyclosedRNAringsproducedfromback-splicingofprecursormRNAineukaryotes.Recentstudies,usingbothcomputationalandexperimentalapproaches,haveallowedadvancedcharacterizationofcircRNAs,leadingtheresearchfieldintoaneweraandsheddinglightonthecontributionofcircRNAstodisease.CircularizationdiversifiesthetranscriptomeCircularRNAs(circRNAs)arisethrough‘out-of-order’splicing,whichinvolvescovalentligationbetweenthedownstream5′splicesitesandtheupstream3′splicesitesofprecursormessengerRNA(pre-mRNA;aprocesscalledback-splicing)[1].Ineffect,thegenerationofcircRNAsdiversifiestheeukaryotictranscriptome,in-creasingthefunctionalcapacityofagene.circRNAsaregenerallyexpressedatlowerabundancelevelsthanlin-eartranscripts,anduntilrecentyears,theywereviewedassplicingnoiseorligationartifacts.Theycanbecircular-izedfrommanygenomicsources,includingexons(ecircRNA),introns(ciRNA),exon-introns(EIciRNA),orfusiontranscripts(f-circRNA)ofparentalgenes.circRNAexpressioniswidespreadamongeukaryoticorganisms,butimportantlyexhibitscell-specificandtissue-specificpatterns.Specificfactorsareinvolvedintheregulationofcir-cRNAbiogenesis[1],aprocessthatinvolvesthespliceoso-malsplicingmechanismwhereinRNA-bindingproteinsparticipateintheformationofcircRNAsbybindingtoandprobablystabilizingtheback-splicingprocess.ThesplicingfactorQuaking(QKI)hasbeendemonstratedtoregulateavarietyofcircRNAsthatareinvolvedinthe©TheAuthor(s).2019OpenAccessThisarticleisdistributedunderthetermsoftheCreativeCommonsAttribution4.0InternationalLicense(http://creativecommons.org/licenses/by/4.0/),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedyougiveappropriatecredittotheoriginalauthor(s)andthesource,providealinktotheCreativeCommonslicense,andindicateifchangesweremade.TheCreativeCommonsPublicDomainDedicationwaiver(http://creativecommons.org/publicdoma...
