FANCD2-FANCI surveys DNA and recognizes double- to single-stranded junctions

• 成果类型: Article
• 署名作者: Alcon, Pablo; Kaczmarczyk, Artur P.; Ray, Korak Kumar; Liolios, Themistoklis; Guilbaud, Guillaume; Sijacki, Tamara; Shen, Yichao; McLaughlin, Stephen H.; Sale, Julian E.; Knipscheer, Puck; Rueda, David S.; Passmore, Lori A.
• 署名单位: MRC Laboratory Molecular Biology; Imperial College London; Royal Netherlands Academy of Arts & Sciences; Hubrecht Institute (KNAW); Utrecht University; Utrecht University Medical Center
• 刊物名称: Nature
• ISSN/ISSBN: 0028-3803
• DOI: 10.1038/s41586-024-07770-w
• 发表日期: 2024-08-29
• 页码: 1165-+
• 关键词: replication; proteins; complex; mechanism; repair; activation; diffusion; SYSTEM

摘要

DNA crosslinks block DNA replication and are repaired by the Fanconi anaemia pathway. The FANCD2-FANCI (D2-I) protein complex is central to this process as it initiates repair by coordinating DNA incisions around the lesion(1). However, D2-I is also known to have a more general role in DNA repair and in protecting stalled replication forks from unscheduled degradation(2-4). At present, it is unclear how DNA crosslinks are recognized and how D2-I functions in replication fork protection. Here, using single-molecule imaging, we show that D2-I is a sliding clamp that binds to and diffuses on double-stranded DNA. Notably, sliding D2-I stalls on encountering single-stranded-double-stranded (ss-ds) DNA junctions, structures that are generated when replication forks stall at DNA lesions(5). Using cryogenic electron microscopy, we determined structures of D2-I on DNA that show that stalled D2-I makes specific interactions with the ss-dsDNA junction that are distinct from those made by sliding D2-I. Thus, D2-I surveys dsDNA and, when it reaches an ssDNA gap, it specifically clamps onto ss-dsDNA junctions. Because ss-dsDNA junctions are found at stalled replication forks, D2-I can identify sites of DNA damage. Therefore, our data provide a unified molecular mechanism that reconciles the roles of D2-I in the recognition and protection of stalled replication forks in several DNA repair pathways.