Qhov sib txawv tseem ceeb ntawm kev sib koom ua ke tsis yog homologous thiab homologous ncaj qha rov ua dua yog qhov kev sib koom ua ke tsis muaj homologous yog txoj hauv kev uas kho ob txoj hlua khi hauv DNA uas tsis tas yuav tsum muaj homologous qauv los qhia kev kho, thaum homologous ncaj qha rov ua dua yog txoj hauv kev. uas kho ob-strand lov nyob rau hauv DNA uas yuav tsum tau ib tug homologous template los coj kev kho.
kho DNA yog txheej txheem uas lub cell txheeb xyuas thiab kho qhov kev puas tsuaj rau DNA molecules. Feem ntau, ib txwm ua haujlwm metabolic thiab ib puag ncig yam xws li hluav taws xob tuaj yeem ua rau DNA puas. Cov xwm txheej no tuaj yeem ua rau ntau txhiab tus neeg mob molecular ib leeg ib hnub. DNA ob-strand lov kho txoj hauv kev yog DNA kho txoj hauv kev hauv cov hlwb. Muaj ob DNA ob-strand lov kho txoj kev raws li nonhomologous kawg koom thiab homologous ncaj qha rov.
Txoj kev tsis sib haum xeeb yog dab tsi?
Nonhomologous kawg koom nrog (NHEJ) yog ib txoj hauv kev uas kho ob txoj hlua khi hauv DNA thiab tsis tas yuav tsum muaj homologous template los kho. Txoj kev no tau pom los ntawm Moore thiab Haber hauv xyoo 1966. Txoj kev no feem ntau yog coj los ntawm luv luv homologous DNA sequences (microhomologies) uas feem ntau muaj nyob rau hauv ib leeg-stranded overhangs ntawm qhov kawg ntawm ob-strand so. Thaum lub overhangs tau sib xws, NHEJ txoj kev kho ob txoj hlua tawg kom raug. Txawm li cas los xij, thaum lub overhangs tsis zoo sib xws, nws ua rau kev kho tsis meej uas yuav ua rau poob ntawm nucleotides. Txoj hauv kev tsis tsim nyog NHEJ tuaj yeem ua rau kev hloov pauv, telomere fusions, thiab cov cim ntawm cov qog hlwb.
Daim duab 01: Tsis yog homologous End Joining
NHEJ txoj kev muaj peb kauj ruam tseem ceeb: kawg khi & tethering, kawg ua, thiab ligation. Hauv cov tsiaj nyeg, cov proteins hu ua Mre11-Rad50-Nbs1 (MRN), DNA- PKcs, Ku (Ku70 & 80) tau koom nrog hauv kev sib tw kawg. Cov kauj ruam ua tiav kawg suav nrog kev tshem tawm cov nucleotides tsis sib haum lossis puas tsuaj thiab rov ua dua tshiab ntawm DNA los ntawm DNA polymerases (gap-filling). Kev tshem tawm cov nucleotides tsis sib haum lossis puas tsuaj yog ua los ntawm nucleases xws li Artemis. X tsev neeg DNA polymerases Pol λ thiab μ hauv cov tsiaj nyeg nqa tawm qhov sib txawv. Kev ua tiav tsis tsim nyog yog tias qhov kawg twb tau sib xws thiab muaj 3'hydorxyl lossis 5'phosphate termini. Tsis tas li ntawd, cov kauj ruam kawg ligation yog ua los ntawm ligation complex IV uas muaj DNA ligase IV thiab nws cov cofactor XRCC4.
Homologous Direct Repeat yog dab tsi?
Homologous direct repeat (HDR) yog ib txoj hauv kev uas kho ob txoj hlua khi hauv DNA nrog kev siv homologous template los qhia kev kho. Txoj kev zoo tshaj plaws ntawm homologous ncaj qha rov ua dua yog los ntawm homologous recombination. HDR mechanism tsuas yog ua tau thaum muaj ib qho homologous DNA nyob rau hauv lub nucleus, feem ntau nyob rau hauv G2 thiab S theem ntawm lub voj voog ntawm tes. Txoj kev lom neeg ntawm HDR pib nrog phosphorylation ntawm histone protein hu ua H2AX nyob rau hauv thaj chaw uas DNA ob-strand tawg tshwm sim. Qhov no attracts lwm cov proteins mus rau qhov chaw puas. Tom qab ntawd MRN complex khi rau qhov xaus thiab tiv thaiv chromosomal so. MRN complex tseem ua kom tawg tag ua ke. Tom qab ntawd, DNA xaus tau ua tiav raws li txoj hauv kev uas tsis tsim nyog seem ntawm pawg tshuaj raug tshem tawm, thiab ib leeg-strand overhangs raug tsim.
Daim duab 02: Homologous Direct Repeat
Txhua daim ntawm ib leeg-kab DNA yog them los ntawm cov protein hu ua RPA, thiab nws txoj haujlwm yog ua kom cov DNA ib leeg nyob ruaj khov. Tom qab no, Rad51 hloov RPA protein. Ntxiv mus, thaum ua hauj lwm ua ke nrog BRCA2, Rad51 khub niam txiv ib tug ntxiv DNA piece uas invades lub tawg DNA strand los tsim ib tug qauv rau DNA polymerase. Lub DNA polymerase tau tuav mus rau DNA los ntawm lwm cov protein hu ua PCNA. Thaum kawg, cov polymerase synthesizes qhov ploj ntawm cov hlua tawg. Tsis tas li ntawd, thaum lub strand tawg yog resynthesized, ob strands yuav tsum uncouple dua. Cov qauv rau ntau txoj kev ntawm uncoupling yog qhia. Tom qab cov hlua sib cais, cov txheej txheem tiav.
Dab tsi yog qhov zoo sib xws ntawm Nonhomologous End Joining thiab Homologous Direct Repeat?
- Nonhomologous kawg koom nrog thiab homologous ncaj qha rov yog ob DNA ob-strand lov kho txoj kev.
- MRN complex koom nrog ob txoj hauv kev.
- Nucleases koom nrog ob txoj hauv kev.
- DNA polymerases koom nrog ob txoj hauv kev.
- Cov txheej txheem no tuaj yeem pom hauv ob qho tib si prokaryotes thiab eukaryotes.
- Lawv yog ob qho tib si tseem ceeb rau kev ciaj sia ntawm tes.
Qhov txawv ntawm Nonhomologous End Joining thiab Homologous Direct Repeat?
Nonhomologous kawg koom nrog yog ib txoj hauv kev uas kho ob txoj hlua khi hauv DNA uas tsis tas yuav muaj homologous template los qhia kev kho, thaum homologous ncaj qha rov ua dua yog txoj hauv kev uas kho ob txoj hlua khi hauv DNA siv homologous template. Yog li, qhov no yog qhov sib txawv tseem ceeb ntawm kev sib koom ua ke tsis yog homologous thiab homologous ncaj qha rov ua dua. Tsis tas li ntawd, homologous recombination tsis koom nrog kev sib koom ua ke tsis yog homologous, thaum homologous recombination yog koom nrog hauv homologous ncaj qha rov ua dua.
Cov lus qhia hauv qab no nthuav tawm qhov sib txawv ntawm qhov tsis sib xws ntawm kev sib koom ua ke thiab homologous ncaj qha rov ua dua hauv daim ntawv tabular rau ib sab ntawm kev sib piv.
Summary – Nonhomologous End Joining vs Homologous Direct Repeat
kho DNA tuaj yeem ua tiav los ntawm cov txheej txheem sib txawv xws li kev thim rov qab ncaj qha, kho ib qho kev puas tsuaj, kho ob txoj hlua tawg, thiab kev hloov pauv hloov. Nonhomologous kawg koom nrog thiab homologous ncaj qha rov ua dua yog ob DNA ob-strand lov kho txoj hauv kev. Nonhomologous kawg koom tsis tas yuav tsum muaj homologous template los coj txoj hauv kev kho DNA. Homologous direct repeat yog ib txoj hauv kev uas yuav tsum muaj homologous template los coj DNA kho. Yog li, qhov no yog qhov sib txawv tseem ceeb ntawm kev sib koom ua ke tsis yog homologous thiab homologous ncaj qha rov ua dua.
