Delagoutte Emmanuelle, Fuchs Robert P P, Bertrand-Burggraf Elisabeth
CNRS, Cancérogenèse Moléculaire et Structurale, ESBS conventionnée avec I'Université Louis Pasteur de Strasbourg UPR 9003, Boulevard Sébastien Brandt, 67400 Strasbourg-Illkirch, France.
J Mol Biol. 2002 Jun 28;320(1):73-84. doi: 10.1016/S0022-2836(02)00401-1.
In Escherichia coli nucleotide excision repair, the UvrB-DNA preincision complex plays a key role, linking adduct recognition to incision. We previously showed that the efficiency of the incision is inversely related to the stability of the preincision complex. We postulated that an isomerization reaction converts [UvrB-DNA], stable but incompetent for incision, into the [UvrB-DNA]' complex, unstable and competent for incision. Here, we identify two parameters, negative supercoiling and presence of a nick at the fifth phosphodiester bond 3' to the lesion, that accelerate the isomerization leading to an increasing incision efficiency. We also show that the [UvrB-DNA] complex is more resistant to a salt concentration increase than the [UvrB-DNA]' complex. Finally, we report that the [UvrB-DNA]' is recognized by UvrC. These data suggest that the isomerization reaction leads to an exposure of single-stranded DNA around the lesion. This newly exposed single-stranded DNA serves as a binding site and substrate for the UvrC endonuclease. We propose that the isomerization reaction is responsible for coupling UvrB and UvrC activities and that this reaction corresponds to the binding of ATP.
在大肠杆菌核苷酸切除修复过程中，UvrB - DNA预切口复合物起着关键作用，将加合物识别与切口连接起来。我们之前表明，切口效率与预切口复合物的稳定性呈负相关。我们推测，一种异构化反应将稳定但无法进行切口的[UvrB - DNA]转化为不稳定且能够进行切口的[UvrB - DNA]'复合物。在此，我们确定了两个参数，即负超螺旋和损伤位点3'端第五个磷酸二酯键处存在切口，它们会加速异构化，从而提高切口效率。我们还表明，[UvrB - DNA]复合物比[UvrB - DNA]'复合物对盐浓度增加更具抗性。最后，我们报告[UvrB - DNA]'被UvrC识别。这些数据表明，异构化反应导致损伤周围单链DNA的暴露。这种新暴露的单链DNA作为UvrC核酸内切酶的结合位点和底物。我们提出，异构化反应负责耦合UvrB和UvrC的活性，并且该反应对应于ATP的结合。
