Department of Functional Genomics and Cancer Biology, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale, Laboratory of Medical Genetics, University of Strasbourg, 67404 Illkirch Cedex, France.
Proc Natl Acad Sci U S A. 2013 Jun 18;110(25):E2261-70. doi: 10.1073/pnas.1220071110. Epub 2013 Jun 3.
Cockayne syndrome type B ATPase (CSB) belongs to the SwItch/Sucrose nonfermentable family. Its mutations are linked to Cockayne syndrome phenotypes and classically are thought to be caused by defects in transcription-coupled repair, a subtype of DNA repair. Here we show that after UV-C irradiation, immediate early genes such as activating transcription factor 3 (ATF3) are overexpressed. Although the ATF3 target genes, including dihydrofolate reductase (DHFR), were unable to recover RNA synthesis in CSB-deficient cells, transcription was restored rapidly in normal cells. There the synthesis of DHFR mRNA restarts on the arrival of RNA polymerase II and CSB and the subsequent release of ATF3 from its cAMP response element/ATF target site. In CSB-deficient cells ATF3 remains bound to the promoter, thereby preventing the arrival of polymerase II and the restart of transcription. Silencing of ATF3, as well as stable introduction of wild-type CSB, restores RNA synthesis in UV-irradiated CSB cells, suggesting that, in addition to its role in DNA repair, CSB activity likely is involved in the reversal of inhibitory properties on a gene-promoter region. We present strong experimental data supporting our view that the transcriptional defects observed in UV-irradiated CSB cells are largely the result of a permanent transcriptional repression of a certain set of genes in addition to some defect in DNA repair.
B 型 Cockayne 综合征 ATP 酶（CSB）属于开关/蔗糖非发酵家族。其突变与 Cockayne 综合征表型有关，经典地认为是由转录偶联修复缺陷引起的，转录偶联修复是 DNA 修复的一种亚型。在这里，我们表明，在 UV-C 照射后，立即早期基因如激活转录因子 3（ATF3）过表达。尽管 ATF3 的靶基因，包括二氢叶酸还原酶（DHFR），无法在 CSB 缺陷细胞中恢复 RNA 合成，但在正常细胞中，转录迅速恢复。在那里，DHFR mRNA 的合成在 RNA 聚合酶 II 和 CSB 的到达后重新开始，随后 ATF3 从其 cAMP 反应元件/ATF 靶位点释放。在 CSB 缺陷细胞中，ATF3 仍然结合在启动子上，从而阻止聚合酶 II 的到达和转录的重新启动。ATF3 的沉默以及野生型 CSB 的稳定引入，恢复了 UV 照射的 CSB 细胞中的 RNA 合成，表明除了在 DNA 修复中的作用外，CSB 活性可能还涉及到逆转基因启动子区域的抑制特性。我们提供了强有力的实验数据支持我们的观点，即在 UV 照射的 CSB 细胞中观察到的转录缺陷主要是由于除了 DNA 修复中的某些缺陷之外，某些基因的永久性转录抑制。
