Hauv txhua yam kab mob (tshwj tsis yog qee tus kab mob), kev siv cov khoom siv caj ces tshwm sim raws li DNA-RNA-protein system. Nyob rau thawj theem, cov ntaub ntawv rov sau dua (tshaj tawm) los ntawm ib qho nucleic acid mus rau lwm qhov. Cov proteins uas tswj cov txheej txheem no yog hu ua transcription factor.
Dab tsi yog kev txhais lus
Kev txhais lus yog biosynthesis ntawm RNA molecule raws li DNA qauv. Qhov no yog ua tau vim complementarity ntawm tej yam nitrogenous bases uas tsim nucleic acids. Synthesis yog ua los ntawm cov enzymes tshwj xeeb - RNA polymerases thiab tswj los ntawm ntau cov proteins tswj.
Tag nrho cov genome tsis tau sau ib zaug, tab sis tsuas yog ib feem ntawm nws, hu ua transcripton. Cov tom kawg suav nrog tus neeg txhawb nqa (qhov chaw txuas ntawm RNA polymerase) thiab lub terminator (ib ntu uas ua kom tiav cov synthesis).
Prokaryotic transcripton yog ib qho operon uas muaj ntau yam genes (cistrons). Raws li nws, polycistronic RNA yog synthesized,muaj cov ntaub ntawv hais txog cov amino acid sib lawv liag ntawm ib pab pawg neeg muaj feem xyuam nrog cov proteins. Eukaryotic transcripton tsuas muaj ib lub noob xwb.
Lub luag haujlwm lom neeg ntawm cov txheej txheem kev hloov pauv yog tsim cov qauv RNA ib ntus, raws li cov protein synthesis (txhais lus) tau ua hauv ribosomes.
RNA synthesis hauv prokaryotes thiab eukaryotes
RNA synthesis tswvyim yog tib yam rau txhua yam kab mob thiab suav nrog 3 theem:
- Kev pib - txuas ntawm cov polymerase rau tus txhawb nqa, ua kom cov txheej txheem.
- Elongation - txuas ntxiv ntawm cov saw hlau nucleotide nyob rau hauv kev coj ntawm 3' mus rau 5' kawg nrog kaw ntawm phosphodiester bonds ntawm nitrogenous bases, uas yog xaiv complementary rau DNA monomers.
- Termination yog ua tiav cov txheej txheem synthesis.
Nyob rau hauv prokaryotes, txhua hom RNA yog transcribed los ntawm ib RNA polymerase, muaj tsib protomers (β, β', ω thiab ob α subunits), uas ua ke ua ib tug core-enzyme muaj peev xwm nce cov saw ntawm ribonucleotides.. Kuj tseem muaj chav tsev ntxiv σ, yam tsis muaj qhov txuas ntawm polymerase rau tus txhawb nqa yog tsis yooj yim sua. Lub complex ntawm cov tub ntxhais thiab cov sigma yam yog hu ua ib tug holoenzyme.
Txawm tias qhov tseeb tias σ subunit tsis yog ib txwm cuam tshuam nrog cov tub ntxhais, nws suav tias yog ib feem ntawm RNA polymerase. Hauv lub xeev dissociated, sigma tsis tuaj yeem khi rau tus txhawb nqa, tsuas yog ib feem ntawm holoenzyme. Tom qab ua tiav qhov pib, tus protomer no cais tawm ntawm lub hauv paus, raug hloov los ntawm ib qho elongation factor.
Txoj Kevprokaryotes yog kev sib xyaw ua ke ntawm kev txhais lus thiab cov txheej txheem sau ntawv. Ribosomes tam sim ntawd koom nrog RNA uas pib ua ke thiab tsim cov saw amino acid. Kev sau ntawv nres vim tsim cov qauv hairpin hauv thaj tsam terminator. Nyob rau theem no, DNA-polymerase-RNA complex tawg.
Hauv cov hlwb eukaryotic, kev hloov pauv yog nqa los ntawm peb lub enzymes:
- RNA polymerase l - synthesizes 28S thiab 18S-ribosomal RNA.
- RNA polymerase ll - rnscribes genes encoding proteins thiab me me nuclear RNAs.
- RNA polymerase lll - lub luag haujlwm rau kev sib txuas ntawm tRNA thiab 5S rRNA (me me subunit ntawm ribosomes).
Tsis muaj ib qho ntawm cov enzymes no muaj peev xwm pib sau cov ntaub ntawv yam tsis muaj kev koom tes ntawm cov proteins tshwj xeeb uas muab kev cuam tshuam nrog tus txhawb nqa. Lub ntsiab ntawm cov txheej txheem yog tib yam li nyob rau hauv prokaryotes, tab sis txhua theem yog ntau nyuaj nrog kev koom tes ntawm ib tug loj tus naj npawb ntawm kev ua hauj lwm thiab kev tswj cov ntsiab lus, nrog rau cov chromatin-hloov sawv daws yuav. Nyob rau theem pib ib leeg, kwv yees li ib puas proteins tau koom nrog, suav nrog ntau yam kev hloov pauv, thaum nyob hauv cov kab mob, ib qho sigma subunit txaus los khi rau tus txhawb nqa thiab qee zaum xav tau kev pab los ntawm activator.
Qhov kev koom tes tseem ceeb tshaj plaws ntawm lub luag haujlwm lom neeg ntawm kev hloov pauv hauv biosynthesis ntawm ntau hom proteins txiav txim siab qhov xav tau rau kev tswj hwm cov noob nyeem.
Kev cai lij choj
Tsis muaj xovtooj ntawm tes yog cov khoom siv caj ces pom tau tag nrho: tsuas yog ib feem ntawm cov noob tau sau tseg, thaum tus so tsis ua haujlwm. Qhov no yog ua tau ua tsaug rau lub complexCov txheej txheem tswj hwm uas txiav txim siab los ntawm cov ntu DNA twg thiab nyob rau hauv dab tsi ntau npaum li cas RNA sequences yuav raug synthesized.
Nyob rau hauv cov kab mob unicellular, qhov kev ua haujlwm sib txawv ntawm cov noob muaj qhov hloov tau zoo, thaum nyob rau hauv ntau cov kab mob nws kuj txiav txim siab cov txheej txheem ntawm embryogenesis thiab ontogenesis, thaum sib txawv ntawm cov ntaub so ntswg raug tsim los ntawm ib lub genome.
Gene kev qhia yog tswj tau ntawm ob peb theem. Cov kauj ruam tseem ceeb tshaj plaws yog txoj cai ntawm kev hloov pauv. Lub ntsiab lus lom neeg ntawm cov txheej txheem no yog tswj hwm qhov xav tau ntawm ntau cov proteins uas xav tau los ntawm lub xov tooj ntawm tes lossis kab mob hauv lub sijhawm tshwj xeeb ntawm kev muaj sia nyob.
Muaj kev hloov pauv ntawm biosynthesis ntawm lwm qib, xws li kev ua, kev txhais lus thiab thauj RNA los ntawm cov nucleus mus rau cytoplasm (tom kawg yog tsis nyob hauv prokaryotes). Thaum tswj tau zoo, cov kab ke no yog lub luag haujlwm rau kev tsim cov protein raws li cov noob taum, uas yog lub ntsiab lus lom neeg ntawm kev sau ntawv. Txawm li cas los xij, nyob rau txhua theem cov saw hlau tuaj yeem raug ncua. Qee qhov kev tswj hwm hauv eukaryotes (lwm txoj kev txhawb nqa, kev sib txuas, kev hloov pauv ntawm cov chaw polyadenellation) ua rau pom qhov sib txawv ntawm cov protein molecules raws li tib DNA ib ntus.
Txij li thaum tsim RNA yog thawj kauj ruam hauv kev txiav txim siab ntawm cov ntaub ntawv caj ces ntawm txoj hauv kev rau cov protein biosynthesis, lub luag haujlwm lom neeg ntawm cov txheej txheem kev hloov pauv hauv kev hloov pauv phenotype ntawm tes yog qhov tseem ceeb tshaj li kev tswj hwm kev ua lossis kev txhais lus..
Kev txiav txim siab ntawm cov haujlwm ntawm cov noob tshwj xeeb xws li hauvnyob rau hauv ob qho tib si prokaryotes thiab eukaryotes, nws tshwm sim nyob rau theem pib nrog kev pab los ntawm cov keyboards tshwj xeeb, uas suav nrog cov cheeb tsam tswj hwm ntawm DNA thiab cov xwm txheej hloov pauv (TFs). Kev ua haujlwm ntawm cov keyboards no tsis yog kev ywj pheej, tab sis yog nyob rau hauv kev tswj hwm nruj ntawm lwm lub xov tooj ntawm tes. Kuj tseem muaj cov txheej txheem ntawm kev tswj tsis tau tshwj xeeb ntawm RNA synthesis, uas ua kom qhov kev pib ib txwm muaj, elongation thiab txiav tawm.
Lub tswvyim ntawm kev hloov pauv hloov pauv
Tsis zoo li cov cai tswj hwm ntawm cov genome, cov khoom siv hloov pauv yog cov tshuaj lom neeg cov protein. Los ntawm kev khi rau cov cheeb tsam tshwj xeeb ntawm DNA, lawv tuaj yeem qhib, cuam tshuam, ua kom nrawm lossis qeeb cov txheej txheem kev sau npe.
Nyob ntawm cov txiaj ntsig tsim tawm, cov txheej txheem hloov pauv ntawm prokaryotes thiab eukaryotes tuaj yeem muab faib ua ob pawg: activators (initiate lossis nce qhov kev siv ntawm RNA synthesis) thiab cov tshuaj tiv thaiv (suppress lossis inhibit tus txheej txheem). Tam sim no, ntau tshaj 2000 TFs tau pom nyob rau hauv ntau yam kab mob.
Kev cai lij choj hauv prokaryotes
Nyob rau hauv prokaryotes, kev tswj ntawm RNA synthesis feem ntau tshwm sim nyob rau theem pib vim muaj kev cuam tshuam ntawm TF nrog ib cheeb tsam tshwj xeeb ntawm cov ntawv sau - tus neeg teb xov tooj uas nyob ib sab ntawm tus txhawb nqa (qee zaum cuam tshuam nrog nws) thiab, Qhov tseeb, yog qhov chaw tsaws rau kev tswj hwm cov protein (activator lossis repressor). Cov kab mob no yog tus cwj pwm los ntawm lwm txoj hauv kev ntawm kev tswj hwm ntawm cov noob - kev sib txuas ntawm lwm txoj kev σ-subunits npaj rau ntau pawg neeg txhawb nqa.
Ib feem operon qhiatuaj yeem tswj tau ntawm cov theem ntawm elongation thiab txiav tawm, tab sis tsis yog vim DNA-binding TFs, tab sis vim yog cov protein cuam tshuam nrog RNA polymerase. Cov no suav nrog Gre proteins thiab anti-terminator yam Nus thiab RfaH.
Kev elongation thiab txiav tawm ntawm kev sau npe hauv prokaryotes yog cuam tshuam rau hauv ib txoj hauv kev los ntawm kev sib txuas ntawm cov protein sib txuas. Hauv eukaryotes, ob qho tib si cov txheej txheem no lawv tus kheej thiab cov ntawv sau thiab kev txhais lus tau sib cais, uas txhais tau hais tias lawv tsis muaj feem cuam tshuam.
Cov neeg ua haujlwm thiab cov neeg tawm tsam
Prokaryotes muaj ob lub tswv yim ntawm kev hloov pauv kev cai ntawm theem pib:
- zoo - nqa los ntawm activator proteins;
- negative - tswj los ntawm cov neeg tawm tsam.
Thaum qhov xwm txheej tau tswj hwm zoo, qhov txuas ntawm qhov tseem ceeb rau tus neeg teb xov tooj qhib lub noob, thiab thaum nws tsis zoo, ntawm qhov tsis sib xws, nws tig tawm. Lub peev xwm ntawm kev tswj hwm cov protein los khi rau DNA nyob ntawm qhov txuas ntawm ligand. Lub luag hauj lwm ntawm tom kawg yog feem ntau ua si los ntawm qhov hnyav molecular cellular metabolites, uas nyob rau hauv cov ntaub ntawv no ua raws li coactivators thiab corepressors.
Lub tshuab ua haujlwm ntawm tus neeg tawm tsam yog nyob ntawm kev sib tshooj ntawm cov neeg txhawb nqa thiab cov neeg ua haujlwm hauv cheeb tsam. Hauv kev ua haujlwm nrog cov qauv no, qhov txuas ntawm cov protein ntau rau DNA kaw ib feem ntawm qhov chaw tsaws rau RNA polymerase, tiv thaiv tom kawg los ntawm kev pib sau ntawv.
Cov activators ua haujlwm ntawm cov neeg ua haujlwm tsis muaj zog, tsis muaj peev xwm txhawb nqa uas tsis pom zoo los ntawm RNA polymerases lossis nyuaj rau yaj (khib helix strandsDNA yuav tsum tau pib transcription). Los ntawm kev koom nrog tus neeg teb xov tooj, cov khoom lag luam protein cuam tshuam nrog cov polymerase, ua rau muaj qhov tshwm sim ntawm qhov pib. Activators muaj peev xwm nce qhov kev siv ntawm kev sau ntawv los ntawm 1000 zaug.
Qee cov prokaryotic TFs tuaj yeem ua raws li ob qho tib si activators thiab cov neeg tawm tsam nyob ntawm qhov chaw ntawm tus neeg teb xov tooj cuam tshuam nrog tus neeg txhawb nqa: yog tias cov cheeb tsam sib tshooj, qhov cuam tshuam cuam tshuam, txwv tsis pub nws ua rau.
| Ligand muaj nuj nqi nrog rau qhov tseem ceeb | Ligand xeev | Neegative regulation | Txoj Cai Zoo |
| Kev cais tawm ntawm DNA | Join | Tshem tawm ntawm cov protein repressor, ua kom cov noob | Kev tshem tawm cov activator protein, noob kaw |
| Ntxiv cov khoom rau DNA | Delete | Kev tshem tawm, kev sau ntawv suav nrog | Tshem tawm activator, tua cov lus sau tseg |
Cov kev cai tsis zoo tuaj yeem txiav txim siab ntawm qhov piv txwv ntawm tryptophan operon ntawm cov kab mob E. coli, uas yog tus cwj pwm los ntawm qhov chaw ntawm tus neeg teb xov tooj nyob rau hauv qhov kev txhawb nqa ib ntus. Lub repressor protein yog qhib los ntawm kev sib txuas ntawm ob lub tryptophan molecules, uas hloov lub kaum sab xis ntawm DNA-binding domain kom nws thiaj li nkag mus rau qhov loj groove ntawm ob lub helix. Ntawm qhov tsis tshua muaj siab ntawm tryptophan, tus neeg tawm tsam poob nws cov ligand thiab ua tsis muaj zog dua. Nyob rau hauv lwm yam lus, zaus ntawm transcription pibinversely proportional rau tus nqi ntawm cov metabolite.
Qee cov kab mob operons (piv txwv li, lactose) muab cov txheej txheem tswj zoo thiab tsis zoo. Xws li ib tug system yog tsim nyog thaum ib lub teeb liab tsis txaus rau rational tswj ntawm kev qhia. Yog li, lactose operon encodes enzymes uas thauj mus rau hauv lub cell thiab ces zom lactose, lwm lub zog uas tsis muaj txiaj ntsig ntau dua li qabzib. Yog li ntawd, tsuas yog nyob rau hauv ib tug tsawg concentration ntawm cov tom kawg, cov protein CAP khi rau DNA thiab pib transcription. Txawm li cas los xij, qhov no yog qhov pom zoo tsuas yog nyob rau hauv lub xub ntiag ntawm lactose, qhov tsis muaj uas ua rau kev ua kom lub Lac repressor, uas thaiv kev nkag mus ntawm cov polymerase rau cov neeg txhawb nqa txawm nyob rau hauv lub xub ntiag ntawm ib tug functional daim ntawv ntawm activator protein.
Vim cov qauv operon hauv cov kab mob, ntau lub noob tau tswj los ntawm ib cheeb tsam tswj hwm thiab 1-2 TFs, thaum nyob rau hauv eukaryotes, ib lub noob muaj ntau cov kev tswj hwm, txhua qhov yog nyob ntawm ntau lwm yam. yam. Qhov nyuaj no sib haum mus rau theem siab ntawm lub koom haum ntawm eukaryotes, thiab tshwj xeeb tshaj yog cov kab mob multicellular.
Txoj cai ntawm mRNA synthesis hauv eukaryotes
Kev tswj hwm ntawm eukaryotic gene qhia yog txiav txim siab los ntawm kev sib koom ua ke ntawm ob lub ntsiab lus: protein transcription facts (TF) thiab kev tswj hwm DNA ib ntus uas tuaj yeem nyob ib sab ntawm tus txhawb nqa, ntau dua li nws, hauv intros lossis tom qab lub gene (lub ntsiab lus cheeb tsam coding, thiab tsis yog ib tug noob nyob rau hauv nws tag nrho cov ntsiab lus).
Qee qhov chaw ua raws li kev hloov pauv, lwm tus tsis cuam tshuamncaj qha nrog TF, tab sis muab cov DNA molecule qhov yooj yim tsim nyog rau kev tsim lub voj-zoo li cov qauv uas nrog rau cov txheej txheem ntawm transcriptional activation. Cov cheeb tsam zoo li no hu ua spacers. Tag nrho cov txheej txheem tswj hwm ua ke nrog cov neeg txhawb nqa ua rau thaj tsam tswj cov noob.
Nws yog ib qho tsim nyog sau cia tias qhov kev txiav txim ntawm qhov kev hloov pauv ntawm lawv tus kheej tsuas yog ib feem ntawm txoj kev tswj hwm ntau theem ntawm cov caj ces, uas muaj ntau cov ntsiab lus ntxiv mus rau qhov tshwm sim vector, uas txiav txim siab seb RNA puas yuav Nws thiaj li raug tsim los ntawm ib cheeb tsam ntawm genome.
Ib qho ntxiv hauv kev tswj hwm kev hloov pauv hauv lub xov tooj ntawm tes yog qhov hloov pauv hauv cov qauv ntawm chromatin. Ntawm no, tag nrho cov kev cai (muab los ntawm kev faib tawm ntawm heterochromatin thiab euchromatin cheeb tsam) thiab cov kev cai hauv cheeb tsam cuam tshuam nrog cov noob tshwj xeeb tam sim no. Rau polymerase ua haujlwm, txhua qib ntawm DNA compaction, suav nrog nucleosome, yuav tsum raug tshem tawm.
Kev sib txawv ntawm cov txheej txheem hloov pauv hauv eukaryotes yog cuam tshuam nrog ntau tus neeg tswj hwm, uas suav nrog amplifiers, silencers (enhancers thiab silencers), nrog rau cov khoom siv hluav taws xob thiab cov khoom siv hluav taws xob. Cov chaw no tuaj yeem nyob ze thiab nyob deb ntawm cov noob (txog 50 txhiab bp).
Txhim kho, silencers thiab adapter ntsiab
Kev Txhim Kho yog luv luv DNA uas muaj peev xwm ua rau muaj kev hloov pauv thaum cuam tshuam nrog kev tswj hwm cov protein. Kwv yees ntawm lub amplifier rau thaj tsam txhawb nqa ntawm cov noobyog ua los ntawm kev tsim lub voj-zoo li cov qauv ntawm DNA. Kev khi ntawm tus activator rau ib qho kev txhim kho los txhawb kev sib dhos ntawm qhov pib ua haujlwm lossis pab cov polymerase mus rau elongation.
Tus txhim kho muaj cov qauv tsim thiab muaj ntau qhov chaw, txhua tus muaj nws tus kheej tswj hwm cov protein.
Silencers yog thaj tsam DNA uas txwv lossis tsis suav nrog qhov muaj peev xwm ntawm kev sau ntawv. Lub mechanism ntawm kev ua hauj lwm ntawm xws li ib tug hloov yog tseem tsis paub. Ib qho ntawm txoj kev xav yog kev ua haujlwm ntawm thaj chaw loj ntawm DNA los ntawm cov protein tshwj xeeb ntawm pab pawg SIR, uas thaiv kev nkag mus rau qhov pib pib. Nyob rau hauv cov ntaub ntawv no, tag nrho cov noob nyob rau hauv ib tug ob peb txhiab lub hauv paus khub ntawm lub silencer raug muab tua.
Adapter cov ntsiab lus ua ke nrog TFs uas khi rau lawv tsim ib chav sib cais ntawm cov caj ces hloov pauv uas xaiv teb rau cov tshuaj hormones steroid, cyclic AMP thiab glucocorticoids. Qhov kev tswj xyuas qhov thaiv no yog lub luag haujlwm rau lub xovtooj ntawm cov lus teb rau kev poob siab, raug rau cov hlau thiab qee yam tshuaj lom neeg.
Ntawm cov cheeb tsam DNA tswj hwm, lwm hom ntsiab lus txawv - insulators. Cov no yog cov kab ke tshwj xeeb uas tiv thaiv kev hloov pauv los ntawm kev cuam tshuam cov noob nyob deb. Lub mechanism ntawm kev txiav txim ntawm insulators tseem tsis tau elucidated.
Eukaryotic transcription factors
Yog tias cov ntaub ntawv hloov pauv hauv cov kab mob tsuas muaj kev tswj hwm, tom qab ntawd hauv cov hlwb nuclear muaj tag nrho cov pab pawg TFs uas muab kev pib keeb kwm yav dhau los, tab sis tib lub sijhawm ncaj qha nyob ntawm kev khi rauDNA tswj cov proteins. Tus naj npawb thiab ntau yam ntawm cov tom kawg hauv eukaryotes yog loj heev. Yog li, nyob rau hauv tib neeg lub cev, qhov kev faib ua feem ntawm cov sequences encoding protein transcription yam yog hais txog 10% ntawm cov genome.
Txog hnub tim, eukaryotic TFs tsis tau nkag siab zoo, zoo li yog cov txheej txheem ntawm kev ua haujlwm ntawm cov caj ces hloov, cov qauv uas nyuaj dua li cov qauv ntawm kev tswj hwm zoo thiab tsis zoo hauv cov kab mob. Tsis zoo li yav tas los, kev ua haujlwm ntawm cov xovtooj ntawm tes tsis cuam tshuam tsis yog los ntawm ib lossis ob, tab sis los ntawm ntau thiab ntau pua lub cim uas tuaj yeem sib koom ua ke, tsis muaj zog lossis tsis suav nrog ib leeg.
Ntawm ib sab, kev ua kom muaj cov noob tshwj xeeb yuav tsum muaj tag nrho cov pab pawg ntawm cov txheej txheem hloov pauv, tab sis ntawm qhov tod tes, ib qho kev tswj hwm cov protein yuav txaus los ua kom pom ntau cov noob los ntawm cascade mechanism. Tag nrho cov kab ke no yog lub khoos phis tawj nyuaj uas ua cov cim los ntawm ntau qhov chaw (ob qho tib si sab nraud thiab sab hauv) thiab ntxiv lawv cov teebmeem rau qhov kawg tshwm sim nrog lub cim ntxiv lossis rho tawm.
Txoj cai hloov pauv cov ntsiab lus hauv eukaryotes (cov neeg ua haujlwm thiab cov neeg tawm tsam) tsis cuam tshuam nrog tus neeg teb xov tooj, xws li hauv cov kab mob, tab sis nrog cov chaw tswj kev sib cais ntawm DNA thiab cuam tshuam rau kev pib los ntawm cov neeg nruab nrab, uas tuaj yeem yog cov neeg nruab nrab cov proteins, cov yam ntxwv ntawm kev pib ua haujlwm. thiab enzymes uas hloov cov qauv ntawm chromatin.
Txawm qhov kev zam ntawm qee qhov TFs suav nrog hauv qhov kev pib ua ntej, txhua yam kev hloov pauv muaj DNA-binding domain uas txawvlawv los ntawm ntau lwm cov proteins uas ua kom muaj qhov zoo ib yam ntawm cov ntawv sau los yog ua tus neeg nruab nrab hauv nws txoj cai.
Cov kev tshawb fawb tsis ntev los no tau pom tias eukaryotic TFs tuaj yeem cuam tshuam tsis yog qhov pib xwb tab sis kuj tseem muaj qhov elongation ntawm transcription.
Ntau yam thiab kev faib tawm
Nyob rau hauv eukaryotes, muaj 2 pawg ntawm cov protein transcription yam: basal (lwm yam hu ua general lossis main) thiab kev tswj hwm. Cov qub yog lub luag haujlwm rau kev lees paub ntawm cov neeg txhawb nqa thiab kev tsim cov txheej txheem ua ntej pib. Yuav tsum pib transcription. Cov pab pawg no suav nrog ntau lub kaum os cov proteins uas ib txwm muaj nyob hauv lub cell thiab tsis cuam tshuam rau qhov sib txawv ntawm cov noob.
Qhov nyuaj ntawm basal transcription yam yog cov cuab yeej zoo sib xws hauv kev ua haujlwm rau sigma subunit hauv cov kab mob, tsuas yog nyuaj thiab tsim nyog rau txhua hom kev txhawb nqa.
Yam ntawm lwm hom cuam tshuam rau kev sau los ntawm kev cuam tshuam nrog kev tswj hwm DNA ib ntus. Txij li cov enzymes no yog cov noob tshwj xeeb, muaj ntau ntawm lawv. Los ntawm kev khi rau thaj tsam ntawm cov noob tshwj xeeb, lawv tswj kev tso tawm ntawm qee cov proteins.
Kev faib tawm ntawm cov khoom hloov pauv hauv eukaryotes yog ua raws li peb lub hauv paus ntsiab lus:
- mechanism of action;
- functioning condition;
- qauv ntawm DNA-binding domain.
Raws li thawj qhov tshwj xeeb, muaj 2 chav kawm ntawm yam: basal (kev cuam tshuam nrog tus txhawb nqa) thiab khi rau thaj tsam sab saud (cov cheeb tsam tswj hwm nyob rau sab saud ntawm cov noob). Hom noKev faib tawm qhov tseem ceeb sib haum rau kev faib ua haujlwm ntawm TF rau hauv dav dav thiab tshwj xeeb. Upstream yam raug muab faib ua 2 pawg nyob ntawm qhov xav tau kev ua kom ntxiv.
Raws li cov yam ntxwv ntawm kev ua haujlwm, kev tsim TFs yog qhov txawv (ib txwm muaj nyob rau hauv ib lub xovtooj ntawm tes) thiab inducible (tsis yog yam ntxwv ntawm txhua hom cell thiab tej zaum yuav xav tau qee yam kev ua kom muaj zog). Cov yam ntxwv ntawm cov pab pawg thib ob, nyob rau hauv lem, muab faib ua cell-specific (sib koom nyob rau hauv ontogeny, yog tus cwj pwm los ntawm nruj kev coj cwj pwm, tab sis tsis yuav tsum tau kom activation) thiab teeb liab-dependent. Cov tom kawg yog sib txawv raws li hom thiab hom kev ua ntawm lub teeb liab ua kom muaj zog.
Cov qauv kev faib tawm ntawm cov protein hloov pauv yog qhov dav heev thiab suav nrog 6 superclasses, uas suav nrog ntau chav kawm thiab tsev neeg.
Txoj Cai Ua Haujlwm
Kev ua haujlwm ntawm cov yam tseem ceeb hauv paus yog kev sib sau ua ke ntawm ntau lub subunits nrog kev tsim ntawm kev pib ua haujlwm thiab ua kom muaj kev hloov pauv. Qhov tseeb, cov txheej txheem no yog cov kauj ruam kawg hauv kev ua ntawm activator protein.
Cov xwm txheej tshwj xeeb tuaj yeem tswj hwm kev sau ntawv hauv ob kauj ruam:
- sib dhos ntawm txoj kev pib ua haujlwm;
- kev hloov mus rau kev tsim khoom elongation.
Hauv thawj kis, kev ua haujlwm ntawm TFs tshwj xeeb raug txo qis rau thawj qhov kev hloov pauv ntawm chromatin, nrog rau kev nrhiav neeg ua haujlwm, kev taw qhia thiab kev hloov kho ntawm tus neeg nruab nrab, polymerase thiab basal yam ntawm tus txhawb nqa, uas ua rau kev ua kom muaj zog. ntawm transcription. Lub ntsiab tseem ceeb ntawm cov teeb liab kis tau tus mob yog tus neeg nruab nrab - ib tug complex ntawm 24 subunits ua nyob rau hauvRaws li tus neeg nruab nrab ntawm kev tswj hwm cov protein thiab RNA polymerase. Cov kab ke ntawm kev sib cuam tshuam yog tus kheej rau txhua tus noob thiab nws qhov sib thooj.
Txoj cai ntawm elongation yog ua tiav vim muaj kev cuam tshuam ntawm qhov zoo nrog P-Tef-b protein, uas pab RNA polymerase kov yeej qhov kev ncua cuam tshuam nrog kev txhawb nqa.
Functional structures of TF
Cov ntsiab lus hloov pauv muaj cov qauv qauv thiab ua lawv txoj haujlwm los ntawm peb qhov kev ua haujlwm:
- DNA-binding (DBD) - xav tau rau kev lees paub thiab kev cuam tshuam nrog thaj tsam tswj hwm ntawm cov noob.
- Trans-activating (TAD) - tso cai rau kev sib cuam tshuam nrog lwm yam kev tswj hwm cov proteins, suav nrog cov txheej txheem hloov pauv.
- Signal-Recognizing (SSD) - xav tau rau kev nkag siab thiab kev xa xov ntawm kev tswj cov cim.
Thiab, qhov DNA-binding domain muaj ntau hom. Lub hom phiaj tseem ceeb hauv nws cov qauv suav nrog:
- "zinc ntiv tes";
- homeodomain;
- "β"-layers;
- loops;
- "leucine xob laim";
- spiral-loop-kauv;
- spiral-tig-kauv.
Ua tsaug rau lub npe no, qhov kev hloov pauv tau "nyeem" DNA nucleotide ib ntus hauv daim ntawv ntawm tus qauv ntawm qhov chaw ntawm ob lub helix. Vim li no, kev lees paub tshwj xeeb ntawm qee yam kev tswj hwm yog ua tau.
Kev sib cuam tshuam ntawm motifs nrog DNA helix yog raws li kev sib raug zoo ntawm qhov chaw ntawm cov nomolecules.
Regulation and synthesis of TF
Muaj ntau txoj hauv kev los tswj cov kev cuam tshuam ntawm kev hloov pauv ntawm cov ntawv sau. Cov no suav nrog:
- ua kom - kev hloov pauv hauv kev ua haujlwm ntawm qhov cuam tshuam nrog DNA vim phosphorylation, ligand txuas lossis cuam tshuam nrog lwm cov proteins tswj hwm (xws li TF);
- translocation - thauj ib yam ntawm cytoplasm mus rau lub nucleus;
- muaj nyob ntawm qhov chaw khi - nyob ntawm qib ntawm chromatin condensation (hauv lub xeev ntawm heterochromatin, DNA tsis muaj rau TF);
- ib txoj hauv kev ntawm cov txheej txheem uas tseem yog cov yam ntxwv ntawm lwm cov proteins (kev tswj hwm ntawm txhua qhov txheej txheem los ntawm kev hloov pauv mus rau kev hloov pauv tom qab kev hloov pauv thiab intracellular localization).
Txoj kev kawg txiav txim siab qhov ntau thiab qhov zoo ntawm cov khoom hloov pauv hauv txhua lub xov tooj. Qee cov TFs muaj peev xwm tswj tau lawv cov synthesis raws li cov lus tawm tswv yim classical, thaum nws tus kheej cov khoom ua ib qho inhibitor ntawm cov tshuaj tiv thaiv. Nyob rau hauv cov ntaub ntawv no, ib tug tej yam concentration ntawm qhov tseem ceeb nres lub transcription ntawm cov noob encoding nws.
Cov ntsiab lus tseem ceeb tshaj plaws
Cov yam tseem ceeb no yog qhov tsim nyog los pib qhov kev hloov pauv ntawm cov noob thiab raug xaiv nyob rau hauv lub npe xws li TFl, TFll thiab TFlll nyob ntawm seb hom RNA polymerase uas lawv cuam tshuam. Txhua yam muaj xws li ob peb subunits.
Basal TFs ua peb lub luag haujlwm tseem ceeb:
- qhov chaw raug ntawm RNA polymerase ntawm tus txhawb nqa;
- unwinding ntawm DNA chains nyob rau hauv cheeb tsam ntawm pib ntawm transcription;
- liberation ntawm polymerase los ntawmtxhawb nqa thaum lub sijhawm hloov mus rau elongation;
Qee lub subunits ntawm basal transcription yam khi rau kev txhawb nqa cov cai tswj hwm. Qhov tseem ceeb tshaj plaws yog lub thawv TATA (tsis yog yam ntxwv ntawm tag nrho cov noob), nyob ntawm qhov deb ntawm "-35" nucleotides los ntawm qhov pib. Lwm qhov chaw sib khi muaj xws li INR, BRE thiab DPE ib ntus. Qee cov TFs tsis ncaj qha hu rau DNA.
Pab pawg ntawm cov ntsiab lus tseem ceeb ntawm RNA polymerase ll suav nrog TFllD, TFllB, TFllF, TFllE thiab TFllH. Tsab ntawv Latin nyob rau qhov kawg ntawm lub npe qhia qhov kev txiav txim ntawm kev kuaj pom cov proteins. Yog li, qhov tseem ceeb TFlllA, uas belongs rau lll RNA polymerase, yog thawj zaug raug cais tawm.
| Npe | Ntau cov protein subunits | Function |
| TFllD | 16 (TBP +15 TAFs) | TBP khi rau TATA lub thawv thiab TAFs paub txog lwm yam kev txhawb nqa |
| TFllB | 1 | Paub txog BRE lub caij, raug taw qhia polymerase ntawm qhov chaw pib |
| TFllF | 3 | Stabilizes polymerase kev sib cuam tshuam nrog TBP thiab TFllB, txhawb kev txuas ntawm TFllE thiab TFllH |
| TFllE | 2 | Txuas thiab kho TFllH |
| TFllH | 10 | Sib cais DNA chains ntawm qhov pib, tso RNA-synthesizing enzyme los ntawm kev txhawb nqa thiab cov ntsiab lus tseem ceeb (biochemistrytxheej txheem yog raws li phosphorylation ntawm Cer5-C-terminal domain ntawm RNA polymerase) |
Kev sib sau ntawm basal TF tshwm sim tsuas yog nrog kev pab ntawm tus activator, tus neeg nruab nrab thiab chromatin-modifying proteins.
Specific TF
Los ntawm kev tswj hwm ntawm caj ces, cov kev hloov pauv no tswj hwm cov txheej txheem biosynthetic ntawm ob tus neeg lub hlwb thiab tag nrho cov kab mob, los ntawm embryogenesis mus rau nplua phenotypic adaptation rau kev hloov ib puag ncig. Lub zog ntawm kev cuam tshuam ntawm TF suav nrog 3 qhov tseem ceeb:
- kev loj hlob (embryo- thiab ontogeny);
- cell voj voog;
- teb rau cov teeb liab sab nraud.
Ib pawg tshwj xeeb ntawm cov txheej txheem hloov pauv tswj hwm qhov sib txawv ntawm morphological ntawm lub embryo. Cov txheej txheem protein no yog encoded los ntawm qhov tshwj xeeb 180 bp kev pom zoo ib ntus hu ua homeobox.
txhawm rau txiav txim siab seb cov noob twg yuav tsum tau sau tseg, cov txheej txheem tswj hwm yuav tsum "nrhiav" thiab khi rau ib qho chaw DNA tshwj xeeb uas ua raws li kev hloov pauv caj ces (txhim kho, tso suab, thiab lwm yam). Txhua qhov xwm txheej no sib raug rau ib lossis ntau qhov cuam tshuam txog kev hloov pauv uas lees paub qhov chaw xav tau vim yog qhov sib txuam ntawm cov tshuaj lom neeg sib txawv ntawm ib ntu sab nraud ntawm helix thiab DNA-binding domain (lub ntsiab lus tseem ceeb). Rau kev lees paub, ib cheeb tsam ntawm cov qauv tseem ceeb ntawm DNA hu ua qhov zawj loj yog siv.
Tom qab khi rau DNA uaactivator protein ua ib tug series ntawm successive kauj ruam ua rau lub rooj sib txoos ntawm preinitiator complex. Cov txheej txheem dav dav ntawm cov txheej txheem no yog raws li hauv qab no:
- Tus neeg ua haujlwm khi rau chromatin hauv cheeb tsam txhawb nqa, nrhiav neeg ua haujlwm ntawm ATP-dependent rearrangement complexes.
- Chromatin rearrangement, ua kom cov protein hloov pauv histone.
- Covalent hloov kho ntawm histones, attraction ntawm lwm yam activator proteins.
- Txhim kho cov protein ntau ntxiv rau thaj tsam tswj hwm ntawm cov noob.
- Kev koom tes ntawm tus neeg nruab nrab thiab tus thawj coj TF.
- Kev sib sau ua ntej ntawm kev pib ua ntej ntawm kev txhawb nqa.
- Kev cuam tshuam ntawm lwm cov activator proteins, rov kho cov subunits ntawm pre-initiation complex.
- Start transcription.
Qhov kev txiav txim ntawm cov xwm txheej no yuav txawv ntawm noob mus rau noob.
Rau ntau lub tshuab ua kom muaj zog muaj ntau qhov sib npaug sib npaug ntawm txoj kev tsim txom. Ntawd yog, los ntawm inhibiting ib qho ntawm cov theem ntawm txoj kev pib, kev tswj hwm cov protein tuaj yeem txo nws cov txiaj ntsig los yog tag nrho thaiv nws. Feem ntau, tus neeg ntxeev siab qhib ntau lub tswv yim ib zaug, lav qhov tsis muaj kev hloov pauv.
Kev tswj hwm cov noob
Txawm hais tias txhua daim ntawv teev lus muaj nws tus kheej txoj cai, eukaryotes muaj cov txheej txheem uas tso cai, zoo li cov kab mob, pib lossis tso tseg cov pab pawg ntawm cov noob txhawm rau ua haujlwm tshwj xeeb. Qhov no yog ua tiav los ntawm qhov kev txiav txim siab transcription uas ua kom tiav cov kev sib txuasLwm yam kev tswj hwm tsim nyog rau kev ua kom siab tshaj plaws lossis kev tawm tsam ntawm cov noob.
Nyob rau hauv cov ntawv sau raws li kev cai, kev sib cuam tshuam ntawm cov khoom sib txawv ua rau tib cov protein, uas ua raws li cov txiaj ntsig vector. Yog li ntawd, kev ua kom muaj qhov zoo li no cuam tshuam rau ntau lub noob ib zaug. Lub kaw lus ua haujlwm ntawm lub hauv paus ntsiab lus ntawm cascade.
Cov tswv yim ntawm kev tswj hwm kev sib koom tes tuaj yeem txiav txim siab ntawm qhov piv txwv ntawm ontogenetic sib txawv ntawm cov leeg pob txha, cov precursors uas yog myoblasts.
Kev txhais ntawm cov noob encoding cov synthesis ntawm cov proteins yam ntxwv ntawm cov leeg nqaij laus yog tshwm sim los ntawm ib qho ntawm plaub yam myogenic: MyoD, Myf5, MyoG thiab Mrf4. Cov proteins no ua kom cov synthesis ntawm lawv tus kheej thiab ib leeg, thiab tseem suav nrog cov noob rau qhov kev hloov pauv ntxiv Mef2 thiab cov nqaij leeg nqaij. Mef2 koom nrog kev tswj hwm ntawm kev sib txawv ntxiv ntawm myoblasts, thaum tib lub sijhawm tswj cov concentration ntawm myogenic proteins los ntawm kev tawm tswv yim zoo.
