An Soyeong, Kusakabe Masayuki, Kim Hyun-Suk, Kozono Hidetsugu, Cheon Na Young, Kim Jeongeun, Kang Jieun, Jang Sunbok, Sugasawa Kaoru, Schärer Orlando D, Lee Ja Yil
Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea.
Biosignal Research Center and Graduate School of Science, Kobe University, Kobe, Hyogo 657-8501, Japan.
Nucleic Acids Res. 2025 Jun 6;53(11). doi: 10.1093/nar/gkaf463.
Ultraviolet-induced DNA lesions are removed by the nucleotide excision repair (NER) pathway. In global-genome NER (GG-NER), XPC-RAD23B recognizes the lesions and initiates NER. However, cyclobutane pyrimidine dimers (CPDs), which do not significantly destabilize the DNA duplex, are not bound by XPC-RAD23B with high selectivity. Instead, CPD is preferentially sensed by UV-DDB, which is believed to hand over the lesion to XPC-RAD23B via ubiquitination of both proteins. Here, by combining biochemical and single-molecule DNA curtain assays, we investigate the interactions between UV-DDB and XPC-RAD23B on DNA. Surprisingly, we discover that XPC-RAD23B enhances the binding of UV-DDB to DNA. We demonstrate that this enhancement can be attributed to the complex formation of UV-DDB and XPC-RAD23B (UX-complex), which increases the binding affinity of UV-DDB to undamaged DNA. We further show that UV-DDB finds CPDs through one-dimensional (1D) diffusion along DNA. Collectively, the UX-complex enhances UV-DDB loading to DNA to accelerate the search for CPD via 1D diffusion. Moreover, we find that UV-DDB and XPC-RAD23B can bind CPDs as a complex, which facilitates the transfer of CPD. Altogether, our results show that UV-DDB and XPC-RAD23B cooperatively interact for rapid CPD search, providing a new mechanism for lesion search in GG-NER.
紫外线诱导的DNA损伤通过核苷酸切除修复（NER）途径去除。在全基因组NER（GG-NER）中，XPC-RAD23B识别损伤并启动NER。然而，不会使DNA双链体显著不稳定的环丁烷嘧啶二聚体（CPD）不能被XPC-RAD23B高选择性结合。相反，CPD优先被UV-DDB感知，据信UV-DDB通过对两种蛋白质进行泛素化将损伤传递给XPC-RAD23B。在这里，我们通过结合生化和单分子DNA帘检测，研究了UV-DDB与XPC-RAD23B在DNA上的相互作用。令人惊讶的是，我们发现XPC-RAD23B增强了UV-DDB与DNA的结合。我们证明这种增强可归因于UV-DDB与XPC-RAD23B的复合物形成（UX复合物），它增加了UV-DDB与未受损DNA的结合亲和力。我们进一步表明，UV-DDB通过沿DNA的一维（1D）扩散找到CPD。总的来说，UX复合物增强了UV-DDB在DNA上的加载，以通过1D扩散加速对CPD的搜索。此外，我们发现UV-DDB和XPC-RAD23B可以作为复合物结合CPD，这促进了CPD的转移。总之，我们的结果表明，UV-DDB和XPC-RAD23B协同相互作用以快速搜索CPD，为GG-NER中的损伤搜索提供了一种新机制。
