分子医学 蛋白质修饰

ProteinModification

蛋白质修饰Posttranscriptionalmodificationsofinsulin2Posttranscriptionalmodificationsincluding:RemovalofN-MetDisulfidebondformationProteolyticprocessingChemicalmodifications:

Phosphorylation(磷酸化) Acetylation(乙酰化) Methylation(甲基化) Ubiquitination(泛素化) SUMOylation(smallubiquitin-relatedmodifier) Glycosylation(糖基化) Myristylation(十四烷基化)andFarnesylation(法尼基化) ……Formoreinformation,see/wiki/Posttranslational_modification3PTM:fourcategoriesCellResearch(2014)24:143–1604Formoreinformation,see/wiki/Posttranslational_modificationRegulationofactivity

turnactivityonturnactivityoffgenerateadifferentfunction

Protein-proteininteraction

modificationsitemaybeabindinginterfaceSubcellularlocalization

modificationsitemaybeatargetingsignalmodificationmaybeamembraneanchor

Degradationidentifytheproteinfordegradation……Whyareproteinsmodified?5Proteinsneedtobeproperlymodified6Methodstodetectproteinmodifications1Dor2DgelelectrophoresisWesternblot:needspecificantibodyEasternblot:usingprobestodetectlipids,carbohydrate,phosphorylationoranyotherproteinmodificationChIP:ChIP-on-chip;ChIP-SeqMS(massspectrometry)Bioinformatics……7PhosphorylationchangesPIoftheprotein,whichcanbeeasilydetectedon2DgelsMSanalysisofC/EBPβafterinvitrophosphorylationbyMAPKand/orGSK3β

ProcNatlAcadSciUSA.2005,102(28):9766-71WesternblottingofErkDetectionMethods:examples8Histonechiefproteincomponentsofchromatin

H1,H2A,H2B,H3,H4,andH5

posttranslationalmodifications:altertheirinteractionwithDNAandnuclearproteins.

H3&H4:longtails;canbemodifiedatseveralplaces,includingmethylation,acetylation,phosphorylation,ubiquitination,sumoylation,citrullinationandADP-ribosylation. ThecoreofthehistonesH2AandH2Bcanalsobemodified.HistoneCode:hypothesizedtobeacodeconsistingofcovalenthistonetailmodifications

→epigeneticcode

9PatternofHistoneModification10HistoneCodeCell,2013,155:3911HistoneVariantsI.ChromatinRemodeler12PatternofHistoneModification13SitesofHistoneModifications/nsmb/journal/v14/n11/images/nsmb1337-F1.gifII.HistoneModification14Histoneacetylation/deacetylationchangesitsinteractionwithDNA15HistoneAcetylation/deacetylationAcetylationenhancestranscription

H3K9,H3K14DeacetylationrepressestranscriptionThebiologicalconsequenceofmodificationdepends,andisacoordinatedresult16Coordinatedrecruitmentofhistone-modifyingactivitiesII.HistoneModification17HistoneModificationsandHumanDiseasesCoffin-Lowrysyndromeisararegeneticdisordercharacterizedbymentalretardationandabnormalitiesoftheheadandfacialandotherareas.ItiscausedbymutationsintheRSK2gene(histonephosphorylation)andisinheritedasanX-linkeddominantgenetictrait.Malesareusuallymoreseverelyaffectedthanfemales.Rubinstein-Taybisyndromeischaracterizedbyshortstature,moderatetosevereintellectualdisability,distinctivefacialfeatures,andbroadthumbsandfirsttoes.ItiscausedbymutationsinCREB-bindingprotein(histoneacetylation)II.HistoneModification18Methylation(甲基化)

DNAmethylation:typicallyoccursatCpGsites

invertebrates catalyzedbytheenzymeDNAmethyltransferase.

Proteinmethylation:typicallyonarginineorlysine Argininecanbemethylatedonceortwiceby

Peptidylargininemethyltransferases(PRMTs)

Lysinecanbemethylatedonce,twiceorthreetimesbylysinemethyltransferases.

19MethylatedAminoAcidArg(R)Lys(K)20HistoneMethylationcatalyzedbyhistonemethyltransferases(HMT)

servesinepigeneticgeneregulation:Methylationatdifferentsitesofhistonesmayhave

differentfunctionongeneexpression

monomethylation:mostlyactivation(Cell,2007,129:823–37)

dimethylation:H3K79me2,activation(Mol.Cell.Biol,2008,28:2825-39)

trimethylation:mostlyrepression(Cell,2007,129:823–37)

21HistoneDemethylation

Jumonji-domain-containingproteinsLSD1isagenewhichcodesaflavin-dependentmonoamineoxidase,whichcandemethylatemono-anddimethylatedlysines,specificallyH3K4andH3K9.theJumonjidomain-containing(JmjC)histonedemethylasesareabletodemethylatemono-,di-,ortri-methylatedlysines.22Nature.2007,450(7167):309-13.ChIPprocedureJHDM1B/FBXL10isanucleolarproteinthatrepressestranscriptionofribosomalRNAgenes23

HistoneMethylation24Mono-ubiquitination-Regulation:

endocytosis,geneexpression,proteinsorting,subnucleartraffickingMulti-ubiquitination-ProteindegradationUbiquitination(泛素化)25TheoncoproteinSS18-SSX1promotesp53ubiquitinationanddegradationbyenhancingHDM2stability.TransfectionExampleMolCancerRes.2008Jan;6(1):127-38.26SUMOylationSUMO(smallubiquitin-relatedmodifier)proteinsaresmallproteintagsthatareconjugatedtoproteinstomodifytheirfunction.TheubiquitinsystemtagsproteinsfordegradationbytheproteosomebutSUMOconjugationhasarangeofotherfunctions,stabilizingsomeproteinsanda