Gap formation is associated with methyl-directed mismatch correction under conditions of restricted DNA synthesis.
Gap formation is associated with methyl-directed mismatch correction under conditions of restricted DNA synthesis.
复制标题
缺口形成与 DNA 合成受限条件下的甲基定向错配校正相关。
作者：
Su,SS;Grilley,M;Thresher,R;Griffith,J;Modrich,P
在大肠杆菌抽提物中，当通过限制外源脱氧核苷-5 ′-三磷酸的浓度或通过补充链终止的2′，3 ′-二脱氧核苷三磷酸来严重限制修复DNA合成时，含有G-T错配和单个半甲基化d（GATC）位点的共价闭合的环状异源双链体受到有效的甲基定向错配校正。然而，在这些条件下的修复导致在含有错配和d（GATC）位点的分子区域中形成单链缺口。这些发现表明，甲基指导的纠正所需的修复DNA合成可以在错配附近启动，并且它们与涉及d（GATC）位点的3′→5′切除（或链置换），随后在错配附近启动5′→3′修复DNA合成的修复反应最为一致. Keywords：DNA修复，基因转换，错配纠正，诱变.
A covalently closed, circular heteroduplex containing a G – T mismatch and a single hemimethylated d(GATC) site is subject to efficient methyl-directed mismatch correction inEscherichia coliextracts when repair DNA synthesis is severely restricted by limiting the concentration of exogenously supplied deoxyribonucleoside-5′-triphosphates or by supplementing reactions with chain-terminating 2′,3′-dideoxynucleoside triphosphates. However, repair under these conditions results in formation of a single-strand gap in the region of the molecule containing the mismatch and the d(GATC) site. These findings indicate that repair DNA synthesis required for methyl-directed correction can initiate in the vicinity of the mispair, and they are most consistent with a repair reaction involving 3′ → 5′ excision (or strand displacement) from the d(GATC) site followed by 5′ → 3′ repair DNA synthesis initiating in the vicinity of the mismatch.Key words: DNA repair, gene conversion, mismatch correction, mutagenesis.