Qhov Tseem Ceeb Qhov txawv - Kev Kho Tsis Zoo vs Nucleotide Excision Repair
Kaum thiab txhiab tus DNA puas tsuaj tshwm sim hauv lub xovtooj ib hnub. Nws induces hloov mus rau lub cell txheej txheem xws li replication, transcription raws li zoo raws li lub viability ntawm cell. Qee qhov xwm txheej, kev hloov pauv los ntawm cov DNA puas tsuaj tuaj yeem ua rau cov kab mob phem xws li mob qog noj ntshav thiab cov kab mob aging-associated syndromes (piv txwv li: Progeria). Txawm hais tias qhov kev puas tsuaj no, lub xovtooj ntawm tes pib tsim kho cov txheej txheem zoo li cascade hu ua DNA puas cov lus teb. Ob peb DNA kho tshuab tau raug txheeb xyuas nyob rau hauv lub cellular system; cov no yog hu ua Base excision repair (BER), Mismatch repair (MMR), Nucleotide excision repair (NER), Ob chav strand break kho. Nucleotide excision kho yog ib qho kev siv ntau yam uas paub txog qhov loj helix distortion DNA lesions thiab tshem tawm lawv. Ntawm qhov tod tes, kev kho tsis sib haum hloov pauv cov hauv paus tsis sib xws thaum rov ua dua. Qhov sib txawv tseem ceeb ntawm kev kho qhov tsis sib haum xeeb thiab kev kho nucleotide excision kho yog tias nucleotide excision kho (NER) yog siv los tshem tawm pyrimidine dimers tsim los ntawm UV irradiation thiab loj helix lesions tshwm sim los ntawm cov tshuaj adducts thaum lub mismatch kho system plays lub luag haujlwm tseem ceeb hauv kev kho cov misincorporated hauv paus uas muaj. khiav tawm ntawm replication enzymes (DNA polymerase 1) thaum lub sij hawm postreplication. Ntxiv nrog rau cov hauv paus tsis sib haum, MMR system cov proteins kuj tuaj yeem kho qhov ntxig / tshem tawm cov voj voog (IDL) uas yog cov txiaj ntsig ntawm polymerase slippage thaum lub sij hawm rov ua dua ntawm cov txheej txheem DNA rov ua dua.
Nucleotide Excision Repair yog dab tsi?
Qhov tshwj xeeb tshaj plaws ntawm nucleotide excision kho yog tias nws kho qhov hloov pauv nucleotide puas tsuaj los ntawm kev cuam tshuam loj hauv DNA ob lub helix. Nws yog pom nyob rau hauv yuav luag tag nrho cov kab mob uas tau soj ntsuam mus txog rau tam sim no. Uvr A, Uvr B, Uvr C (excinucleases) Uvr D (ib lub helicase) yog cov enzymes paub zoo tshaj plaws koom nrog hauv NER uas ua rau kho DNA hauv cov qauv kab mob Ecoli. Uvr ABC multi-subunits enzyme complex tsim Uvr A, Uvr B, Uvr C polypeptides. Cov noob encoded rau aforementioned polypeptides yog uvr A, uvr B, uvr C. Uvr A thiab B enzymes collectively paub txog kev puas tsuaj induced distortion uas yog tshwm sim rau DNA ob helix xws li pyrimidine dimmers vim UV irradiation. Uvr A yog ATPase enzyme thiab qhov no yog cov tshuaj tiv thaiv autocatalytic. Tom qab ntawd Uvr A tawm ntawm DNA thaum Uvr BC complex (active nuclease) tshem cov DNA ntawm ob sab ntawm kev puas tsuaj uas catalyzed los ntawm ATP. Lwm cov protein hu ua Uvr D encoded los ntawm uvrD noob yog helicase II enzyme unwinds DNA uas tshwm sim los ntawm kev tso tawm ntawm ib qho kev puas tsuaj DNA ntu. Qhov no ua rau muaj qhov sib txawv hauv DNA helix. Tom qab cov ntu puas tau raug tshem tawm, qhov sib txawv ntawm 12-13 nucleotide tseem nyob hauv DNA strand. Qhov no tau sau los ntawm DNA polymerase enzyme I thiab lub nick raug kaw los ntawm DNA ligase. ATP yuav tsum tau nyob ntawm peb kauj ruam ntawm cov tshuaj tiv thaiv no. Cov txheej txheem NER tuaj yeem txheeb xyuas hauv cov tsiaj zoo li tib neeg thiab. Hauv tib neeg, cov tawv nqaij hu ua Xeroderma pigmentosum yog vim DNA dimers los ntawm UV irradiation. Cov noob XPA, XPB, XPC, XPD, XPE, XPF, thiab XPG tsim cov proteins los hloov DNA puas. Cov proteins ntawm cov noob XPA, XPC, XPE, XPF, thiab XPG muaj cov haujlwm nuclease. Ntawm qhov tod tes, cov proteins ntawm XPB thiab XPD cov noob qhia txog cov haujlwm helicase uas analogs rau Uvr D hauv E coli.
Daim duab 01: Nucleotide Excision kho
Kev kho tsis haum yog dab tsi?
Qhov kev kho tsis sib haum yog pib thaum lub sijhawm DNA synthesis. Txawm hais tias muaj kev ua haujlwm € subunit, DNA polymerase III tso cai rau kev koom ua ke ntawm nucleotide tsis ncaj ncees lawm rau kev sib txuas txhua 10 8paj khub. Mismatch kho cov proteins paub cov nucleotide no, excise nws thiab hloov nws nrog qhov tseeb nucleotide lub luag hauj lwm rau qhov kawg ntawm qhov tseeb. DNA methylation yog qhov tseem ceeb rau MMR cov protein kom paub txog cov niam txiv txoj hlua los ntawm cov hlua uas tau tsim tawm tshiab. Lub methylation ntawm adenine (A) nucleotide nyob rau hauv GATC motif ntawm ib tug tshiab synthesized strand yog qeeb me ntsis. Ntawm qhov tod tes, niam txiv strand adenine nucleotide hauv GATC motif twb methylated lawm. MMR cov proteins paub txog cov khoom sib txuas tshiab los ntawm qhov sib txawv ntawm cov niam txiv strand thiab pib kho qhov tsis sib haum nyob rau hauv ib qho tshiab synthesized strand ua ntej nws tau txais methylated. MMR cov proteins coj lawv txoj haujlwm kho kom tshem tawm qhov tsis ncaj ncees lawm nucleotide ua ntej qhov tshiab DNA strand tau txais methylated. Cov enzymes Mut H, Mut L thiab Mut S encoded los ntawm noob mut H, mut L, mut S catalyze cov tshuaj tiv thaiv hauv Ecoli. Mut S protein paub txog xya tawm ntawm yim lub hauv paus tsis sib xws tshwj tsis yog rau C: C, thiab khi rau ntawm qhov chaw ntawm qhov tsis sib xws hauv duplex DNA. Nrog khi ATPs, Mut L thiab Mut S koom nrog txoj hauv kev tom qab. Lub complex translocates ob peb txhiab lub hauv paus khub deb mus txog thaum nws pom ib tug hemimethylated GATC motif. Lub dormant nuclease kev ua ntawm Mut H protein yog qhib thaum nws pom ib tug hemimethylated GATC motif. Nws cleaves lub unmethylated DNA strand tawm hauv 5′ nick ntawm G nucleotide ntawm unmethylated GATC motif (tshiab synthesized DNA strand). Tom qab ntawd tib txoj hlua nyob rau sab nraud ntawm qhov tsis sib haum yog nicked los ntawm Mut H. Nyob rau hauv tas li ntawd mus rau lub so ntawm cov kauj ruam, lub collective ua ntawm Uvr D ib tug helicase protein, Mut U, SSB thiab exonuclease kuv excise lub incorrect nucleotide nyob rau hauv ib leeg-stranded. DNA. Qhov sib txawv uas tau tsim nyob rau hauv qhov kev txiav txim yog sau los ntawm DNA polymerase III thiab kaw los ntawm ligase. Ib qho zoo sib xws tuaj yeem raug txheeb xyuas hauv nas thiab tib neeg. Kev hloov pauv ntawm tib neeg hMLH1, hMSH1, thiab hMSH2 yog koom nrog hauv cov kab mob qog noj ntshav uas tsis yog-polyposis uas deregulates cell division ntawm txoj hnyuv.
Daim duab 02: Kev Kho Tsis Zoo
Dab tsi yog qhov txawv ntawm Kev Kho Tsis Zoo thiab Nucleotide Excision Repair?
Kev kho tsis haum vs Nucleotide Excision Repair |
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| Kev kho qhov tsis sib haum tshwm sim thaum lub sijhawm rov ua dua. | Qhov no yog koom nrog hauv kev tshem tawm pyrimidine dimers vim U. V irradiation & lwm yam DNA lesions vim tshuaj lom neeg. |
| Enzymes | |
| Nws yog catalyzed los ntawm Mut S, Mut L, Mut H, Uvr D, SSB thiab exonuclease I. | Nws yog catalyzed los ntawm Uvr A, Uvr B, Uvr C, UvrD enzymes. |
| Methylation | |
| Nws yog qhov tseem ceeb los pib qhov kev tawm tsam. | DNA methylation tsis tas yuav tsum tau pib qhov tshuaj tiv thaiv. |
| Kev ua ntawm Enzymes | |
| Mut H yog endonuclease. | Uvr B thiab Uvr C yog exonucleases. |
| Qhov no tshwm sim tshwj xeeb thaum rov ua dua. | Qhov no tshwm sim thaum raug U. V lossis tshuaj mutagens, tsis yog thaum rov ua dua |
| Kev ruaj ntseg | |
| Nws tsis yog kev txuag heev. | |
| Gap Filling | |
| Nws yog ua los ntawm DNA polymerase III. | Nws yog ua los ntawm DNA polymerase I. |
Summary – Mismatch Repair vs Nucleotide Excision Repair
kho tsis haum (MMR) thiab Nucleotide excision kho (NER) yog ob lub tswv yim uas tshwm sim hauv cell txhawm rau kho DNA puas thiab cuam tshuam uas tshwm sim los ntawm ntau tus neeg ua haujlwm. Cov no yog cov npe hu ua DNA kho mechanisms. Nucleotide excision kho kho qhov hloov kho nucleotide puas tsuaj, feem ntau yog cov kev puas tsuaj loj ntawm DNA ob chav helix uas tshwm sim vim raug rau UV irradiation thiab tshuaj adducts. Mismatch kho cov proteins paub qhov tsis ncaj ncees lawm nucleotide, excise nws thiab hloov nws nrog qhov tseeb nucleotide. Cov txheej txheem no yog lub luag haujlwm rau qhov kawg ntawm qhov raug thaum rov ua dua.
