Txhua tus uas kawm txog molecular biology, biochemistry, genetic engineering thiab lwm yam kev tshawb fawb txog sai lossis tom qab nug cov lus nug: RNA polymerase lub luag haujlwm yog dab tsi? Qhov no yog lub ntsiab lus nyuaj, uas tseem tsis tau tshawb nrhiav tag nrho, tab sis, txawm li cas los xij, qhov paub zoo yuav raug suav nrog hauv lub ntsiab lus ntawm tsab xov xwm.
cov ntaub ntawv dav dav
Nws yuav tsum nco ntsoov tias muaj RNA polymerase ntawm eukaryotes thiab prokaryotes. Thawj yog ntxiv muab faib ua peb hom, txhua tus yog lub luag haujlwm rau kev hloov pauv ntawm ib pawg ntawm cov noob. Cov enzymes no suav nrog kev yooj yim raws li thawj, thib ob, thiab thib peb RNA polymerases. Lub prokaryote, uas nws cov qauv yog tsis muaj nuclear, thaum lub sij hawm transcription ua raws li lub tswv yim yooj yim. Yog li ntawd, kom paub meej, txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm RNA polymerases yog structurally zoo ib yam. Lawv ntseeg tias muaj tsawg kawg yog 10 polypeptide chains. Nyob rau tib lub sijhawm, RNA polymerase 1 synthesizes (transcripts) noob uas tom qab ntawd yuav raug muab txhais ua ntau yam proteins. Qhov thib ob yog transcribing noob, uas tom qab ntawd muab txhais ua cov proteins. RNA polymerase 3 yog sawv cev los ntawm ntau yam tsis tshua muaj molecular hnyav ruaj khov enzymes uas nruab nrabrhiab heev rau alpha amatine. Tab sis peb tsis tau txiav txim siab seb RNA polymerase yog dab tsi! Qhov no yog lub npe ntawm cov enzymes uas koom nrog hauv kev sib txuas ntawm ribonucleic acid molecules. Hauv kev nkag siab nqaim, qhov no yog hais txog DNA-raws li RNA polymerases uas ua raws li tus qauv deoxyribonucleic acid. Enzymes tseem ceeb heev rau kev ua haujlwm ntev thiab ua tiav ntawm cov kab mob muaj sia. RNA polymerases muaj nyob hauv txhua lub hlwb thiab feem ntau cov kab mob.
Sib faib los ntawm nta
Nyob ntawm cov subunit muaj pes tsawg leeg, RNA polymerases muab faib ua ob pawg:
- Thawj qhov cuam tshuam nrog kev hloov pauv ntawm cov noob me me hauv cov genomes yooj yim. Rau kev ua haujlwm nyob rau hauv rooj plaub no, kev tswj hwm txoj cai tsis tas yuav tsum tau ua. Yog li, qhov no suav nrog tag nrho cov enzymes uas muaj tsuas yog ib qho subunit. Ib qho piv txwv yog RNA polymerase ntawm bacteriophages thiab mitochondria.
- pawg no suav nrog tag nrho RNA polymerases ntawm eukaryotes thiab cov kab mob, uas yog complex. Lawv yog cov sib txawv ntau subunit protein complexes uas tuaj yeem sau ntau txhiab tus noob sib txawv. Thaum lawv ua haujlwm, cov noob no teb rau ntau qhov kev tswj xyuas cov cim uas los ntawm cov protein ntau thiab nucleotides.
Txoj kev faib ua haujlwm zoo li no yog qhov ua tau zoo thiab ua kom yooj yim ntawm lub xeev tiag tiag.
RNA polymerase kuv ua dab tsi?
Lawv tau muab txoj haujlwm ntawm kev tsim thawjrRNA gene transcripts, uas yog, lawv yog qhov tseem ceeb tshaj plaws. Cov yav tas yog paub zoo dua nyob rau hauv lub npe 45S-RNA. Lawv ntev yog kwv yees li 13 txhiab nucleotides. 28S-RNA, 18S-RNA thiab 5,8S-RNA yog tsim los ntawm nws. Vim qhov tseeb tias tsuas yog ib daim ntawv teev lus siv los tsim lawv, lub cev tau txais "kev lees paub" tias cov molecules yuav tsim nyob rau hauv qhov sib npaug. Tib lub sijhawm, tsuas yog 7 txhiab nucleotides siv los tsim RNA ncaj qha. Tus so ntawm cov ntawv sau tseg yog degraded nyob rau hauv lub nucleus. Hais txog xws li ib tug loj residue, muaj ib lub tswv yim hais tias nws yog tsim nyog rau cov theem pib ntawm ribosome tsim. Tus naj npawb ntawm cov polymerases nyob rau hauv cov hlwb ntawm cov tsiaj siab dua hloov pauv ib ncig ntawm 40 txhiab units.
Nws koom li cas?
Yog li, peb twb tau txiav txim siab ua ntej RNA polymerase (prokaryotic qauv ntawm cov molecule). Nyob rau tib lub sijhawm, cov subunits loj, nrog rau ntau ntawm lwm cov high-molecular-weight polypeptides, muaj cov ntsiab lus zoo thiab cov qauv tsim. Thaum lub sijhawm cloning ntawm cov noob thiab kev txiav txim siab ntawm lawv cov qauv tseem ceeb, cov kws tshawb fawb tau txheeb xyuas qhov kev hloov pauv ntawm cov saw hlau. Siv cov lus qhia zoo, cov kws tshawb fawb kuj tau ua qhov kev ntsuam xyuas kev hloov pauv, uas tso cai rau peb tham txog qhov tseem ceeb ntawm kev ua haujlwm ntawm tus kheej. Txhawm rau ua qhov no, siv qhov chaw qhia mutagenesis, tus kheej cov amino acids tau hloov pauv hauv cov saw hlau polypeptide, thiab cov kev hloov pauv no tau siv los ua ke ntawm cov enzymes nrog kev tshuaj xyuas tom qab ntawm cov khoom uas tau txais hauv cov qauv no. Nws tau raug sau tseg tias vim nws lub koom haum, thawj RNA polymerase rauLub xub ntiag ntawm alpha-amatin (ib yam tshuaj lom neeg uas tau los ntawm daj ntseg grebe) tsis hnov tsw.
Kev ua haujlwm
Ob qho tib si thawj thiab thib ob RNA polymerases tuaj yeem muaj nyob hauv ob hom. Ib tug ntawm lawv tuaj yeem ua rau pib qhov kev hloov pauv tshwj xeeb. Qhov thib ob yog DNA nyob ntawm RNA polymerase. Qhov kev sib raug zoo no tau tshwm sim hauv qhov loj ntawm kev ua haujlwm ntawm kev ua haujlwm. Lub ntsiab lus tseem tab tom tshawb nrhiav, tab sis nws twb paub lawm tias nws nyob ntawm ob qho kev hloov pauv, uas tau raug xaiv los ua SL1 thiab UBF. Qhov peculiarity ntawm tom kawg yog tias nws tuaj yeem khi ncaj qha rau tus txhawb nqa, thaum SL1 xav tau muaj UBF. Txawm hais tias nws tau sim pom tias DNA-dependent RNA polymerase tuaj yeem koom nrog hauv kev sau ntawv ntawm qib tsawg thiab tsis muaj qhov tom kawg. Tab sis rau kev ua haujlwm ib txwm ua ntawm cov txheej txheem no, UBF tseem xav tau. Vim li cas tiag? Txog tam sim no, nws tseem tsis tuaj yeem tsim qhov laj thawj rau tus cwj pwm no. Ib qho kev piav qhia nrov tshaj plaws qhia tias UBF ua haujlwm zoo li rDNA transcription stimulator thaum nws loj hlob thiab tsim. Thaum lub sijhawm so tshwm sim, qhov tsawg kawg nkaus uas yuav tsum tau ua ntawm kev ua haujlwm raug tswj xyuas. Thiab rau nws, kev koom tes ntawm kev hloov pauv tsis yog qhov tseem ceeb. Qhov no yog li cas RNA polymerase ua haujlwm. Lub zog ntawm cov enzyme no tso cai rau peb los txhawb cov txheej txheem ntawm kev tsim me me "tsev blocks" ntawm peb lub cev, ua tsaug uas nws tau hloov kho tas li rau xyoo lawm.
pab pawg thib ob ntawm enzymes
Lawv txoj haujlwm yog tswj hwm los ntawm kev sib sau ua ke ntawm ntau cov protein ua ntej pib ua haujlwm ntawm cov neeg txhawb nqa ntawm chav kawm thib ob. Feem ntau qhov no tau qhia hauv kev ua haujlwm nrog cov protein tshwj xeeb - activators. Ib qho piv txwv yog TVR. Cov no yog cov laj thawj cuam tshuam uas yog ib feem ntawm TFIID. Lawv yog lub hom phiaj rau p53, NF kappa B thiab lwm yam. Proteins, uas yog hu ua coactivators, kuj siv lawv lub zog hauv cov txheej txheem ntawm kev tswj hwm. Ib qho piv txwv yog GCN5. Vim li cas cov protein no xav tau? Lawv ua raws li cov adapters uas kho cov kev sib cuam tshuam ntawm activators thiab yam uas muaj nyob rau hauv pre-initiation complex. Nyob rau hauv thiaj li yuav transcription tshwm sim kom raug, muaj qhov tsim nyog pib yam tseem ceeb. Txawm hais tias muaj rau ntawm lawv, tsuas yog ib tus tuaj yeem cuam tshuam ncaj qha nrog tus txhawb nqa. Rau lwm qhov xwm txheej, yuav tsum muaj qhov ua ntej thib ob RNA polymerase complex. Ntxiv mus, thaum lub sij hawm cov txheej txheem no, cov ntsiab lus nyob ze - tsuas yog 50-200 khub ntawm qhov chaw uas transcription pib. Lawv muaj qhov qhia txog kev khi ntawm activator proteins.
Special Features
Puas yog cov qauv subunit ntawm cov enzymes ntawm txawv keeb kwm cuam tshuam rau lawv lub luag haujlwm hauv kev sau ntawv? Tsis muaj lus teb meej rau lo lus nug no, tab sis nws ntseeg tias nws yog qhov zoo tshaj plaws. RNA polymerase nyob ntawm qhov no li cas? Cov haujlwm ntawm cov enzymes ntawm cov qauv yooj yim yog kev hloov pauv ntawm cov noob caj noob ces tsawg (lossis txawm tias lawv qhov me me). Ib qho piv txwv yog cov synthesis ntawm RNA primers ntawm Okazaki fragments. Kev txhawb nqa tshwj xeeb ntawm RNA polymerase ntawm cov kab mob thiab phages yog tias cov enzymes muaj cov qauv yooj yim thiab tsis txawv ntawm ntau haiv neeg. Qhov no tuaj yeem pom nyob rau hauv cov txheej txheem ntawm DNA replication hauv cov kab mob. Txawm hais tias ib tus tuaj yeem xav txog qhov no: thaum cov qauv kev ua haujlwm ntawm cov genome ntawm ib qho T-phage tau kawm, thaum lub sij hawm kev loj hlob ntawm ntau qhov kev hloov pauv ntawm ntau pawg ntawm cov noob tau sau tseg, nws tau qhia tias cov tswv cuab complex RNA polymerase tau siv. rau qhov no. Ntawd yog, ib qho yooj yim enzyme tsis yog induced nyob rau hauv xws li mob. Muaj ntau qhov tshwm sim los ntawm qhov no:
- Eukaryotic thiab kab mob RNA polymerase yuav tsum muaj peev xwm paub txog cov neeg txhawb nqa sib txawv.
- Nws yog qhov tsim nyog uas cov enzymes muaj cov lus teb rau cov protein sib txawv.
- RNA polymerase kuj tseem tuaj yeem hloov pauv qhov tshwj xeeb ntawm kev lees paub ntawm nucleotide ntu ntawm cov qauv DNA. Rau qhov no, siv ntau yam protein effectors.
Los ntawm no ua raws li lub cev xav tau ntxiv "tsev" cov ntsiab lus. Cov proteins ntawm cov kev hloov pauv hloov pauv pab RNA polymerase kom ua tiav nws txoj haujlwm. Qhov no siv, mus rau qhov loj tshaj plaws, rau cov enzymes ntawm ib tug complex qauv, nyob rau hauv lub possibilities ntawm qhov kev siv ntawm ib tug ntau yam kev pab cuam rau kev siv ntawm noob caj noob ces cov ntaub ntawv. Ua tsaug rau ntau yam dej num, peb tuaj yeem soj ntsuam ib hom hierarchy hauv cov qauv ntawm RNA polymerases.
tus txheej txheem sau ntawv ua haujlwm li cas?
Puas muaj gene lub luag haujlwm rau kev sib txuas lus nrogRNA polymerase? Ua ntej, hais txog kev sau ntawv: hauv eukaryotes, cov txheej txheem tshwm sim hauv cov nucleus. Hauv prokaryotes, nws tshwm sim hauv cov kab mob nws tus kheej. Kev sib cuam tshuam ntawm polymerase yog raws li lub hauv paus hauv paus ntsiab lus ntawm kev sib koom ua ke ntawm ib tus neeg molecules. Hais txog cov teeb meem kev sib cuam tshuam, peb tuaj yeem hais tias DNA ua tshwj xeeb ua tus qauv thiab tsis hloov pauv thaum hloov pauv. Txij li DNA yog ib qho tseem ceeb enzyme, nws muaj peev xwm hais tau tseeb hais tias ib tug tshwj xeeb gene yog lub luag hauj lwm rau cov polymer no, tab sis nws yuav ntev heev. Nws yuav tsum tsis txhob hnov qab tias DNA muaj 3.1 billion nucleotide residues. Yog li, nws yuav tsim nyog hais tias txhua hom RNA yog lub luag haujlwm rau nws tus kheej DNA. Rau cov tshuaj tiv thaiv polymerase mus ntxiv, cov khoom siv hluav taws xob thiab ribonucleoside triphosphate substrates yog xav tau. Nyob rau hauv lawv lub xub ntiag, 3', 5'-phosphodiester bonds yog tsim ntawm ribonucleoside monophosphates. Lub RNA molecule pib ua ke nyob rau hauv tej yam DNA sequences (promoters). Cov txheej txheem no xaus rau ntawm ntu ntu (termination). Lub vev xaib uas koom nrog ntawm no yog hu ua cov ntawv sau tseg. Hauv eukaryotes, raws li txoj cai, tsuas muaj ib lub noob ntawm no, thaum prokaryotes tuaj yeem muaj ntau ntu ntawm cov cai. Txhua daim ntawv teev npe muaj ib cheeb tsam tsis muaj ntaub ntawv. Lawv muaj qee cov nucleotide ib ntus uas cuam tshuam nrog cov txheej txheem kev hloov pauv tau hais dhau los.
Kab mob RNA polymerases
Covmicroorganisms ib enzyme yog lub luag haujlwm rau kev sib txuas ntawm mRNA, rRNA thiab tRNA. Qhov nruab nrab polymerase molecule muaj kwv yees li 5 subunits. Ob ntawm lawv ua raws li kev khi cov ntsiab lus ntawm enzyme. Lwm subunit yog koom nrog hauv kev pib ntawm synthesis. Kuj tseem muaj cov enzyme tivthaiv rau cov tsis muaj kev sib txuas rau DNA. Thiab lub subunit kawg yog koom nrog coj RNA polymerase rau hauv daim ntawv ua haujlwm. Nws yuav tsum raug sau tseg tias cov enzyme molecules tsis yog "dawb" ntab hauv cov kab mob cytoplasm. Thaum tsis siv, RNA polymerases khi rau cov cheeb tsam tsis tshwj xeeb ntawm DNA thiab tos kom qhib kev txhawb nqa. Me ntsis digressing los ntawm lub ntsiab lus, nws yuav tsum tau hais tias nws yog heev yooj yim mus kawm cov proteins thiab lawv cov nyhuv ntawm ribonucleic acid polymerases ntawm cov kab mob. Nws yog qhov tshwj xeeb tshaj yog yooj yim rau kev sim rau lawv los txhawb lossis tshem tawm cov ntsiab lus ntawm tus kheej. Vim lawv qhov sib npaug siab, qhov kev xav tau tuaj yeem tau txais sai heev. Alas, tib neeg kev tshawb fawb tsis tuaj yeem ua tiav ntawm tus nqi nrawm vim peb cov qauv sib txawv.
RNA polymerase "kub cag" ua li cas?
Zaj lus no tab tom los rau nws qhov kev txiav txim siab. Kev tsom mus rau eukaryotes. Tab sis kuj muaj archaea thiab kab mob. Yog li ntawd, kuv xav them sai sai rau cov qauv no ntawm lub neej. Hauv lub neej ntawm archaea, tsuas muaj ib pawg ntawm RNA polymerases. Tab sis nws yog qhov zoo sib xws hauv nws cov khoom rau peb lub koom haum ntawm eukaryotes. Ntau tus kws tshawb fawb tau hais tias qhov peb tuaj yeem soj ntsuam hauv archaea yog qhov tiagevolutionary poj koob yawm txwv ntawm tshwj xeeb polymerases. Cov qauv ntawm cov kab mob kuj tseem nthuav. Raws li tau hais dhau los, tsis yog txhua yam kab mob no muaj lawv tus kheej polymerase. Thiab qhov twg nws yog, nws yog ib tug subunit. Viral enzymes tau xav tias tau muab los ntawm DNA polymerases ntau dua li cov RNA complex. Txawm li cas los xij, vim muaj ntau haiv neeg ntawm cov kab mob no, muaj ntau qhov kev siv ntawm cov txheej txheem lom neeg.
Zoo kawg
Alas, tam sim no noob neej tseem tsis tau muaj tag nrho cov ntaub ntawv tsim nyog xav tau kom nkag siab txog genome. Thiab yuav ua li cas! Yuav luag txhua yam kab mob yeej muaj cov caj ces - qhov no feem ntau siv rau cov kab mob uas niaj hnub ua rau peb muaj teeb meem, kis kab mob, thiab lwm yam. Cov kab mob nyuaj tshaj plaws thiab kho tsis tau kuj yog, qhov tseeb, ncaj qha lossis ncaj qha nyob ntawm tib neeg genome. Thaum peb kawm to taub peb tus kheej thiab siv qhov kev paub no rau peb qhov kom zoo dua, ntau yam teeb meem thiab kab mob yuav tsuas tso tseg. Ntau yam kab mob txaus ntshai yav dhau los, xws li kab mob me me thiab kab mob plague, tau dhau los ua ib yam dab tsi dhau los. Npaj mus rau qhov ntawd mumps, hnoos hawb pob. Tab sis peb yuav tsum tsis txhob so, vim peb tseem ntsib ntau yam kev sib tw uas yuav tsum tau teb. Thiab nws yuav raug pom, rau txhua yam tab tom mus rau qhov no.
