Site-specific covalent capture of human O<sup>6</sup>-alkylguanine-DNA-alkyltransferase using single-stranded intrastrand cross-linked DNA
作者:D. K. O'Flaherty、C. J. Wilds
DOI:10.1039/c6ob02246d
日期:——
nsferase (hAGT) to the 3′-end of DNA in excellent yields with short reaction times by using intrastrand cross-linked (IaCL) DNA probes. This strategy exploited the substrate specificity of hAGT to generate the desired DNA–protein covalent complex. IaCL DNA linking two thymidine residues, or linking a thymidine residue to a 2′-deoxyguanosine residue (either in a 5′→3′ or 3′→5′ fashion), lacking a phosphodiester
据报道,通过使用链内交联(IaCL)DNA探针,可在短时间内以优异的产率将人O 6-烷基鸟嘌呤-DNA-烷基转移酶(hAGT)缀合到DNA的3'-末端。该策略利用了hAGT的底物特异性来生成所需的DNA-蛋白质共价复合物。制备了连接两个胸苷残基或将胸苷残基连接至2'-脱氧鸟苷残基(以5'→3'或3'→5'的方式),在交联位点缺少磷酸二酯键的IaCL DNA使用亚磷酰胺策略,然后进行固相合成。相对于未修饰的对照双链体,所有包含模型IaCL的双链体均显示出热稳定性降低。所述Ô 4 -胸苷-亚烷基- ö评估的任何AGT均无法修复4-胸苷和(5'→3') O 6 -2'-脱氧鸟苷-亚烷基-O 4-胸苷IaCL DNA加合物(人AGT和大肠杆菌的同源物,OGT和Ada- C)。(5'→3') O 4-胸苷-亚烷基-O 6含有丁烯或庚烯系链的-2'-脱氧鸟苷IaCL DNA已被人类变异体有效修复,
Preparation of Covalently Linked Complexes Between DNA and <i>O</i><sup>6</sup>-Alkylguanine-DNA Alkyltransferase Using Interstrand Cross-Linked DNA
作者:Francis P. McManus、Amardeep Khaira、Anne M. Noronha、Christopher J. Wilds
DOI:10.1021/bc300553u
日期:2013.2.20
O-6-alkylguanine-DNA alkyltransferases (AGT) are responsible for the removal of alkylation at both the O-6 atom of guanine and O-4 atom of thymine. AGT homologues show vast substrate differences with respect to the size of the adduct and which alkylated atoms they can restore. The human AGT (hAGT) has poor capabilities for removal of methylation at the O-4 atom of thymidine, which is not the case in most homologues. No structural data are available to explain this poor hAGT repair. We prepared and characterized O(6)G-butylene-(OT)-T-4 (XLGT4) and O(6)G-heptylene-(OT)-T-4 (XLGT7) interstrand cross-linked (ICL) DNA as probes for hAGT and the Escherichia coli homologues, OCT and Ada-C, for the formation of DNA-ACT covalent complexes. XLGT7 reacted only with hAGT and did so with a cross-linking efficiency of 25%, while XLGT4 was inert to all ACT tested. The hAGT mediated repair of XLGT7 occurred slowly, on the order of hours as opposed to the repair of O-6-methyl-2'-deoxyguanosine which requires seconds. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the repair reaction revealed the formation of a covalent complex with an observed migration in accordance with a DNA-ACT complex. The identity of this covalent complex, as determined by mass spectrometry, was composed of a heptamethylene bridge between the O-4 atom of thymidine (in an 11-mer DNA strand) to residue Cys145 of hAGT. This procedure can be applied to produce well-defined covalent complexes between ACT with DNA.