Repair Patch Analysis of DNA Mismatch and Loop Repair
Date Issued
2004
Date
2004
Author(s)
Chen, Ying-Kun
DOI
zh-TW
Abstract
Evolutionarily conserved mismatch repair (MMR) systems promote genetic stability in most eukaryotic and prokaryotic organisms by correcting DNA replication errors, antagonizing homeologous recombination between partially diverged DNA sequences, interacting with variety of DNA lesions, and performing other functions. The study about mismatch repair has been analyzed thoroughly. But the large loop repair, a distinct repair from mismatch repair, is an unknown repair system. Studying the differences between these two repair systems seems to be an interesting project.
Both human strand-specific mismatch repair and large loop repair depend on presence of exogenous dNTPs and are inhibited by aphidicolin. Most of previous studies about mismatch repair patches were to trap the intermediates produced from the course of heteroduplex correction in HeLa nuclear extracts either in the absent of exogenous dNTP or in the supplement of aphidicolin. In vitro excision tracts have been mapped as single-strand gaps produced when repair is provoked under condition of restricted DNA synthesis. Analysis of gaps produced on these heteroduplex resulted in excision tracts spanning the path between lesion and the nick. However, according to this methodology, this repair reaction is incomplete. It is not able to eliminate the possibility of the result generated from side reaction caused by the restricted to show that condition.
To avoid the argument, we employed thiophosphate chemistry in the repair patch mapping. Under the condition of dNTPΠ substitution and iodoethanol treatment, mismatch, large loop, or mismatch and large loop co-exist heteroduplexses with 3’ nick showed distinct repair patches. In mismatch repair, the most extreme ladders shift to 5’ direction approximately 100 to 150 bases beyond the mismatch, which is consistent with the excision tract endpoint mapped and agrees with the results of others. In loop repair, the repair signal locates on nick and loop site. These results further ascertain that the repair of mismatch and large loop are processed through different mechanisms. When mismatch and loop co-exist, there is interference between these two repair patches.
Subjects
修復路徑
移除反應
配對錯誤
核酸環修復
DNA修復
核酸修復
mismatch repair
repair patch
DNA repair
thiophosphate chemistry
Loop repair
excision mapping
Type
other
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