Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
Nucleic Acids Res. 2024 Jun 24;52(11):6333-6346. doi: 10.1093/nar/gkae286.
Transcription-coupled repair (TCR) and global genomic repair (GGR) are two subpathways of nucleotide excision repair (NER). The TFIIH subunit Tfb1 contains a Pleckstrin homology domain (PHD), which was shown to interact with one PHD-binding segment (PB) of Rad4 and two PHD-binding segments (PB1 and PB2) of Rad2 in vitro. Whether and how the different Rad2 and Rad4 PBs interact with the same Tfb1 PHD, and whether and how they affect TCR and GGR within the cell remain mysterious. We found that Rad4 PB constitutively interacts with Tfb1 PHD, and the two proteins may function within one module for damage recognition in TCR and GGR. Rad2 PB1 protects Tfb1 from degradation and interacts with Tfb1 PHD at a basal level, presumably within transcription preinitiation complexes when NER is inactive. During a late step of NER, the interaction between Rad2 PB1 and Tfb1 PHD augments, enabling efficient TCR and GGR. Rather than interacting with Tfb1 PHD, Rad2 PB2 constrains the basal interaction between Rad2 PB1 and Tfb1 PHD, thereby weakening the protection of Tfb1 from degradation and enabling rapid augmentation of their interactions within TCR and GGR complexes. Our results shed new light on NER mechanisms.
转录偶联修复 (TCR) 和全基因组修复 (GGR) 是核苷酸切除修复 (NER) 的两个亚途径。TFIIH 亚基 Tfb1 含有一个 Pleckstrin 同源结构域 (PHD)，该结构域已被证明在体外与 Rad4 的一个 PHD 结合片段 (PB) 和 Rad2 的两个 PHD 结合片段 (PB1 和 PB2) 相互作用。不同的 Rad2 和 Rad4 PB 是否以及如何与相同的 Tfb1 PHD 相互作用，以及它们是否以及如何影响细胞内的 TCR 和 GGR 仍然是个谜。我们发现 Rad4 PB 与 Tfb1 PHD 持续相互作用，这两种蛋白可能在 TCR 和 GGR 的损伤识别中作为一个模块发挥作用。Rad2 PB1 保护 Tfb1 免受降解，并在基础水平上与 Tfb1 PHD 相互作用，推测在 NER 不活跃时，在转录起始复合物中。在 NER 的后期步骤中，Rad2 PB1 和 Tfb1 PHD 之间的相互作用增强，从而实现有效的 TCR 和 GGR。Rad2 PB2 不是与 Tfb1 PHD 相互作用，而是限制 Rad2 PB1 和 Tfb1 PHD 之间的基础相互作用，从而削弱 Tfb1 免受降解的保护，并使它们在 TCR 和 GGR 复合物中的相互作用迅速增强。我们的研究结果为 NER 机制提供了新的线索。
