Txhua tus neeg uas kawm cov molecular biology, biochemistry, kev tshuaj ntsuam genetic engineering, thiab ib tug xov tooj ntawm lwm yam kev txawj ntse, ua ntej los yog tom qab ntawd, nug cov nqe lus nug: dab tsi yog qhov muaj nuj nqi ntawm RNA polymerase? Qhov no yog ib tug ncaj complex npe uas yog tseem kiag li unexplored, tab sis, cuaj kaum, nws yog lub npe hu hais tias nws yuav zes raws li ib feem ntawm qhov tsab xov xwm.
lus qhia dav dav
Nws yog tsim nyog yuav tau nco ntsoov hais tias muaj yog RNA polymerase ntawm eukaryotes thiab prokaryotes. Tus thawj yog muab faib ntxiv rau hauv peb lub hom, txhua yam uas yog lub luag hauj lwm rau lub transcription ntawm cov noob cais pab pawg neeg. Cov enzymes yog suav rau simplicity, raws li cov thawj, thib ob thiab thib peb RNA polymerase. Prokaryotes, tus qauv ntawm cov uas tsis yog-nuclear, thaum transcribed ua hauj lwm raws li lub yooj yim zog daim duab. Yog li ntawd, rau clarity, mus ntes kom ntau li ntau tau yuav kho tau eukaryotes. RNA polymerases yog structurally zoo sib xws. Nws yog ntseeg hais tias lawv muaj tsis tsawg tshaj li 10 polypeptide chains. Yog li RNA polymerase synthesizes 1 (transcribes) noob uas yog tom qab txhais mus rau ntau yam proteins. Qhov thib ob koom transcribing noob, uas yog tom qab txhais ua cov proteins. RNA polymerase 3 qhia tau hais tias ntau yam ruaj khov uas tsis muaj molecular yuag enzymes uas muaj mob pesnrab rhiab rau alpha amatinu. Tab sis peb tsis tau txiav txim siab rau li cas xyov yog RNA polymerase! Yog li ntawd hu ua enzymes uas koom nyob rau hauv lub synthesis ntawm ribonucleic acid molecules. Nyob rau hauv lub vos kev txiav txim zoo to taub los ntawm no DNA-dependent RNA polymerase, uas hauj lwm rau lub hauv paus ntawm lub matrix ntawm deoxyribonucleic acid. Enzymes yog qhov tseem ceeb rau ib tug ntev thiab muaj kev vam meej hauj lwm uas muaj sia nyob. RNA polymerase yuav muaj nyob rau hauv tag nrho cov hlwb thiab ntau cov kab mob.
Lub division rau lub specifics
Nyob rau hauv lub subunit muaj pes tsawg leeg ntawm RNA polymerases raug muab faib ua ob pawg:
- Tus thawj deals nrog transcribing ib tug me me muaj pes tsawg tus ntawm cov noob nyob rau hauv lub genomes ntawm tej yam yooj yim. Rau cov lag luam nyob rau hauv cov ntaub ntawv no tsis tau txoj ntxawg tej yam. Yog li ntawd, ntawm no yog hais txog tag nrho cov enzymes uas muaj xws li tsuas yog ib subunit. Raws li ib qho piv txwv muaj peev xwm ntxias cov bacteriophage RNA polymerase thiab mitochondria.
- Qhov no pab pawg neeg no muaj xws li tag nrho cov eukaryotic RNA polymerase thiab cov kab mob, uas yog yooj yim txheej txheem. Lawv yog cov zoo nkauj txhua qhov mnogosubedinichnye protein ntau ceg uas yuav Hour txhiab ntawm txawv noob. Thaum lub sij hawm kev lag luam, cov noob teb rau ib tug loj tus naj npawb ntawm ntxawg Pib ntsais koj teeb uas tau txais los ntawm protein yam thiab nucleotides.
Tej yam ntxwv thiab tej division yog es conditional thiab ib tug simplification ntawm lub tiag tiag qhov teeb meem no.
Li cas rau cov RNA polymerase kuv?
Lawv twb tsau muaj nuj nqi ntawm kev kawm ntawv cov thawj transcripts ntawm rRNA noob, uas yog, lawv yog cov tseem ceeb tshaj plaws. Cov yav tas yog ntau paub nyob rau hauv txoj kev xaiv 45S-RNA. Lawv ntev yog hais txog 13 000 nucleotides. Los ntawm nws yog tsim 28S-RNA, 18S-5.8S RNA-RNA. Vim lub fact tias lawv yog tsim tsuas yog ib transkriptor, lub cev tau txais ib tug "guarantee" hais tias cov molecules yuav tsim nyob rau hauv sib npaug zos nyiaj. Nyob rau tib lub sij hawm lub creation ntawm RNA ncaj qha mus xwb 7000 nucleotides. Tus so ntawm lub transcript yog degraded nyob rau hauv lub nucleus. Nyob rau xws li ib tug loj residue yog ntseeg hais tias nws yog tsim nyog rau hauv thaum ntxov ua sawv ntawm lub tsim ntawm ribosomes. Lub xov tooj ntawm no polymerases nyob rau hauv lub hlwb ntawm ntau dua beings hovering ib ncig ntawm lub cim ntawm 40 txhiab units.
Yuav ua li cas nws yog lub koom haum?
Yog li, peb muaj cov thawj RNA polymerase (prokaryotes-qauv molecules) yog suav tias yog zoo. Nyob rau hauv cov ntaub ntawv no, tus loj subunit, raws li, tseeb, thiab ib tug loj tus naj npawb ntawm lwm cov molecular yuag polypeptides, muaj kom meej meej distinguishable kev haumxeeb thiab yam ntxwv thawj. Thaum lub sij hawm cloning ntawm cov noob thiab los mus txiav txim lawv thawj qauv tau raug qhia los ntawm zaum evolutionarily Conserved feem ntawm chains. Siv ib tug zoo qhia, cov kev soj ntsuam kuj ua mutational tsom xam uas tso cai rau peb los tham txog tej tseem ceeb ntawm ib tug neeg thawj. Rau lub hom phiaj no, siv qhov chaw coj mutagenesis hloov tus neeg polypeptide chains, thiab xws li hloov amino acid subunits siv nyob rau hauv los ua ke ntawm enzymes tom tsom xam cov khoom, uas twb tau nyob rau hauv cov ntaub ntawv lug. Nws tau muab sau tias vim nws lub koom haum ntawm cov thawj RNA polymerase nyob rau hauv lub xub ntiag ntawm alpha-amatina (ib tug heev tshuaj lom tshuaj, uas yog tau los ntawm ib tug daj ntseg toadstool) tsis hnov mob.
tau hauj lwm
Ob tus thawj thiab tus thib ob RNA polymerase zaum yuav muaj nyob rau hauv ob cov ntaub ntawv. Ib tug ntawm lawv muaj peev xwm ua kom pib cov kev transcription. Qhov thib ob - ib tug DNA-dependent RNA polymerase. Qhov no tus cwj pwm yog manifested nyob rau hauv qhov loj tshaj plaws lag luam los ntawm cov kev ua. Subject kawm ntxiv, tab sis tam sim no peb paub hais tias nws nyob rau hauv ob lub transcription yam, uas yog xa mus rau raws li SL1 thiab UBF. Tshwj xeeb tshaj yog lub caij nyoog kawg no - hais tias nws muaj peev xwm sib txuas lus ncaj nraim nrog cov neeg pab txhawb, thaum lub sij hawm SL1 UBF yuav tsum tau muaj. Txawm hais tias nws twb tau experimentally tsim hais tias DNA-dependent RNA polymerase yuav koom nyob rau hauv lub transcription ntawm ib tug tsawg kawg nkaus thiab tsis muaj lub xub ntiag ntawm lub caij nyoog kawg no. Tab sis rau cov qub hauj lwm ntawm no mechanism UBF yog tseem yuav tsum tau. Vim li cas thiaj? Ho kom deb li deb tsis tau tejyam mus nrhiav kom tau qhov ua rau ntawm cov cwj pwm no. Ib qho ntawm feem nrov piav qhia tias UBF pab ib yam ntawm cov hom rDNA transcription thaum nws loj hlob thiab tsim. Thaum so theem no tshwm sim, ces khaws cia tsawg kawg nkaus yuav tsum tau theem ntawm hauj lwm. Ib feem ntawm transcription yam tsis yog ib qho tseem ceeb rau nws. Ntawm no yog li tej hauj lwm RNA polymerase. Cov kev ua ntawm no enzyme tso cai txhawb cov playback ntawm me me "tsev blocks" ntawm lub cev, vim cov uas nws yog tas li tshiab rau decades.
Qhov thib ob pab pawg neeg ntawm enzymes
Lawv tau hauj lwm yog tswj los ntawm lub rooj sib txoos ntawm multiprotein complex preinitsiatornogo promoters ntawm lub thib ob chav kawm ntawv. Feem ntau cov feem ntau qhov no yog hais nyob rau hauv lub chaw ua hauj lwm ntawm qhov tshwj xeeb cov nqaijrog - activators. Raws li ib qho piv txwv yog lub TBP. Nws yog txuam yam tseem ceeb uas yog ib feem ntawm TFIID. Lawv - ib lub hom phiaj rau p53, NF kappa B, thiab hais txog. Nws txhob nyob rau hauv tus txheej txheem ntawm kev cai thiab muab cov nqaijrog hu ua coactivators. Piv txwv yog lub Gcn5. Vim li cas peb yuav tsum tau cov nqaijrog? Lawv pab raws li adapters uas customize sis ntawm activators thiab yam tseem ceeb uas yog nyob rau hauv preinitsiatorny complex. Yuav kom kho transcription tshwm sim, koj yuav tsum muaj qhov tsim nyog initiator yam. Txawm tias muaj tseeb hais tias rau ntawm lawv, ncaj qha nrog cov neeg pab txhawb tej zaum yuav tsuas yog ib qho. Rau lwm tus neeg mob yuav tsum tau preformed complex ntawm ib tug thib ob RNA polymerase. Ntxiv mus, thaum lub sij hawm cov kev yog uas nyob ib sab proximal ntsiab - tsuas yog 50-200 officers ntawm lub chaw nyob qhov twg transcription yog pib. Lawv muaj ib tug hais txog ntawm tus thwj toob ntawm activator proteins.
tej nta
Puas muaj tus subunit qauv ntawm cov enzymes ntawm txawv keeb kwm nyob rau ntawm lawv tej qhov luag hauj lwm nyob rau hauv lub transcription? Lub caij nyoog lo lus teb rau lo lus nug no yog tsis muaj, tab sis ntseeg hais tias nws yuav zoo. Yuav ua li cas puas tau nws muaj feem xyuam rau RNA polymerase? Enzyme zog yooj yim qauv - ib tug tsawg ntau yam ntawm transcription ntawm cov noob (los sis txawm ib tug me me feem). Piv txwv yog lub synthesis ntawm RNA primers Okazaki tawg tsam. Cov promoter tseem ntawm lub RNA polymerases ntawm cov kab mob thiab phages yog tias enzymes yog tuav yooj yim qauv thiab yog ntau haiv neeg. Qhov no yuav pom nyob rau hauv tus txheej txheem ntawm DNA replication nyob rau hauv cov kab mob. Txawm tias peb yuav xav txog qhov no: complex qauv thaum kawm genome T txawm phage, thaum lub sij hawm txoj kev loj hlob, nws tau sau hais tias rov switching ntawm ntau yam noob transcription pawg, nws twb pom hais tias cov complex siv rau qhov no RNA polymerase party. Hais tias yog, ib tug yooj yim enzyme nyob rau hauv xws li mob yog tsis ntxias. Qhov no implies ib tug xov tooj ntawm txim:
- RNA polymerase ntawm eukaryotes thiab cov kab mob yuav tsum tau paub txog qhov sib txawv promoters.
- Nws yog tsim nyog tias enzyme muaj ib tug meej lo lus teb rau txawv cov nqaijrog-regulators.
- RNA polymerase kuj yuav tsum tau hloov tus nrog paub txog lub tseem ntawm lub template DNA nucleotide ib theem zuj zus. Ua li no, siv ib tug ntau yam ntawm protein effectors.
Nws li nram no rau hauv lub cev yuav tau ntxiv "tsev" hais. Cov nqaijrog pab Hour lub complex ntawm RNA polymerase siab nqa tawm nws zog. Qhov no siv tau, feem ntau, cov enzymes complex qauv, nyob rau hauv uas lub possibilities ntawm kev siv ib tug uas nws kim heev kev pab cuam ntawm kev tshuaj ntsuam genetic ntaub ntawv. Vim ntau yam teeb meem, peb yuav soj ntsuam ib yam ntawm cov hierarchy qauv ntawm RNA polymerase.
Yuav ua li cas puas muaj tus txheej txheem ntawm transcription?
Puas muaj ib tug noob lub luag hauj lwm rau cov neeg nrog lub RNA polymerase? Yuav pib ntawm transcription: tus txheej txheem nyob rau hauv eukaryotes yuav siv sij hawm qhov chaw nyob rau hauv lub nucleus. Nyob rau hauv prokaryotes, nws ntws hauv lub microorganism. Cov kev sib raug zoo ntawm cov polymerase yog ib tug yooj yim cov yam ntxwv hauv paus ntsiab lus ntawm ib tug complementary pos ib tug neeg molecules. Nyob rau cov teeb meem ntawm kev sis raug zoo muaj peev xwm hais tias DNA yog yuav luag ib tug template thiab tsis hloov thaum lub sij hawm transcription. Txij li thaum DNA yog ib tug holistic enzyme, qhov tshaj plaws yog tej yam, hais tias ib tug kev noob yog lub luag hauj lwm rau qhov no polymer yuav ua tau, tab sis nws yuav ua tau ib tug ntev heev lub sij hawm. Peb yuav tsum tsis txhob hnov qab tias cov DNA muaj 3.1 billion nucleotide residues. Yog li ntawd, ntau tsim nyog hais tias txhua txhua hom ntawm RNA raws li nws cov DNA. Rau cov ndlwg ntawm cov polymerase cov tshuaj tiv thaiv yuav tsum tau zog thiab ribonukle-ozidtrifosfato substrates. Yog hais tias tej no yog tsim 3 ', 5'-phosphodiester bonds ntawm ribonukleozidmonofosfatami. Molecule RNA synthesis pib nyob rau hauv tej yam DNA sequences (promoters). Cov txheej txheem terminates ntawm txiav qhov chaw (txiav). Lub tsev kawm ntawv, uas yog muab kev koom tes no yog hu ua transcriptional. Nyob rau hauv eukaryotes, muaj yog feem ntau tsuas yog ib qho noob, thaum prokaryotes kuj muaj ntau yam daim code. Txhua transcriptional muaj uninformative cheeb tsam. Lawv nyob tej nucleotide sequences uas nrog transcriptional ntxawg yam hais saum toj no.
Kab mob RNA polymerase
Cov kab mob ib enzyme yog lub luag hauj lwm rau lub synthesis ntawm mRNA, rRNA thiab tRNA. Qhov nruab nrab polymerase molecule muaj ib tug roughly 5 subunits. Ob tug ntawm cov hauj lwm raws li losis tswvyim dabtsi neeg enzyme. Lwm subunit muab kev koom tes nyob rau hauv lub pib ntawm synthesis. Muaj kuj yog ib feem ntawm cov enzyme nonspecific rau kev sib txuas lus nrog DNA. Thiab lub xeem subunit tau nqa lub RNA polymerase nyob rau hauv ib tug ua hauj lwm daim ntawv. Nws yog muab sau tseg tias enzyme molecules yog tsis nyob rau hauv ib tug "free" navigating nyob rau hauv lub cytoplasm ntawm cov kab mob. Thaum RNA polymerases siv, ces lawv khi uas tsis yog-kev DNA cheeb tsam thiab tos kom txog thaum lub active promoter yog qhib. Ib me ntsis distracted los ntawm lub npe, nws yuav tsum tau hais tias tus kab mob no yog heev yooj yim mus kawm cov nqaijrog thiab lawv cawv rau cov ribonucleic acid polymerase. Tshwj xeeb tshaj yog yooj yim rau lawv mus xyaum ua tej yam rau stimulation los yog inhibition ntawm tus neeg hais. Vim lawv cov qib high tu tub tu kiv nqi yuav ua tau kuj sai sai tau cov yam tshwm sim. Alas, cov tib neeg kev tshawb no yuav tsis tau ua nyob rau hauv xws li ib tug ceev ceev pace ua tsaug rau peb cov yam ntxwv muaj ntau haiv neeg.
RNA polymerase "ntes tau" nyob rau hauv ntau yam ntaub ntawv?
Qhov ntawd los mus rau ib tug muaj kuab xaus tsab xov xwm. Lub ntsiab xim tau them mus rau lub eukaryotes. Tab sis tseem muaj archaea thiab kab mob. Yog li ntawd koj xav kom koj them ib tug me ntsis ntawm cov xim thiab cov ntaub ntawv ntawm lub neej. Cov tseem ceeb heev kev ua si ntawm Archean muaj no tsuas muaj ib pab pawg neeg ntawm RNA polymerases. Tab sis nws yog heev uas zoo sib xws nyob rau hauv nws cov khoom nrog peb koom haum ua teb eukaryotes. Muaj ntau zaum twb tau pom tias yog dab tsi peb yuav pom los ntawm cov Arche ua tau ib tug evolutionary txwv zeej txwv koob tshwj xeeb polymerases. Nws tseem yog nthuav, thiab cov qauv ntawm cov kab mob. Raws li yav tas los sau, tsis yog txhua txhua ntawm cov kab mob muaj lawv tus kheej polymerase. Thiab nyob qhov twg nws yog, nws yog ib tug subunit. Nws yog ntseeg hais tias cov kab mob enzymes derived ntawm DNA polymerases, es tsis txhob ntawm complex RNA lug. Txawm tias vim muaj ntau haiv neeg ntawm no pab pawg neeg ntawm kab mob sib txawv siv raws li ib tug muab lom mechanism.
xaus
Alas, tib neeg tsis tau muaj vsoy ntaub ntawv tsim nyog yuav tsum tau rau kev nkag siab txog lub genome. Thiab hais tias tsuas yog nws yuav tau ua li cas! Yuav luag tag nrho cov kab mob yeej cia li ib tug kev tshuaj ntsuam genetic hauv paus - qhov no siv tshwj xeeb tshaj yog rau cov kab mob uas yeej muaj muab peb cov teeb meem rau tus kab mob thiab thiaj li nyob. Qhov tseem complex thiab incurable kab mob - lawv yog cov tseem, nyob rau hauv qhov tseeb, ncaj qha los yog kov yog nyob ntawm seb tib neeg genome. Thaum peb kawm kom paub txog rau lawv tus kheej thiab yuav siv txoj kev paub no mus rau cov kev pab ntawm ib tug loj tus naj npawb ntawm cov teeb meem thiab cov kab mob yuav tsuas tu tsis tseg nyob ua ib ke. Tam sim no ib tug tshaj plaws ntawm yav dhau los, muaj ntau yam yav tas los txaus ntshai kab mob xws li smallpox, kab mob plague. Kev npaj mus mumps, hnoos. Tab sis tsis txhob so, vim hais tias peb yuav ntsib nrog ib tug txawm ntau dua xov tooj ntawm txawv txoj kev sib tw hais tias koj yuav tau mus nrhiav cov lus teb. Thiab nws yuav pom, vim hais tias nws yuav mus ua tau li ntawd.