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AND-1 fork protection function prevents fork resection and is essential for proliferation. Nat Commun 2018; 9:3091. [PMID: 30082684 PMCID: PMC6079002 DOI: 10.1038/s41467-018-05586-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 07/13/2018] [Indexed: 12/31/2022] Open
Abstract
AND-1/Ctf4 bridges the CMG helicase and DNA polymerase alpha, facilitating replication. Using an inducible degron system in avian cells, we find that AND-1 depletion is incompatible with proliferation, owing to cells accumulating in G2 with activated DNA damage checkpoint. Replication without AND-1 causes fork speed slow-down and accumulation of long single-stranded DNA (ssDNA) gaps at the replication fork junction, with these regions being converted to DNA double strand breaks (DSBs) in G2. Strikingly, resected forks and DNA damage accumulation in G2, but not fork slow-down, are reverted by treatment with mirin, an MRE11 nuclease inhibitor. Domain analysis of AND-1 further revealed that the HMG box is important for fast replication but not for proliferation, whereas conversely, the WD40 domain prevents fork resection and subsequent DSB-associated lethality. Thus, our findings uncover a fork protection function of AND-1/Ctf4 manifested via the WD40 domain that is essential for proliferation and averts genome instability. AND-1, the vertebrate orthologue of Ctf4, is a critical player during DNA replication and for maintenance of genome integrity. Here the authors use a conditional AND-1 depletion system in avian DT40 cells to reveal the consequences of the lack of AND-1 on cell proliferation and DNA replication.
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Hosono Y, Abe T, Higuchi M, Kajii K, Sakuraba S, Tada S, Enomoto T, Seki M. Tipin functions in the protection against topoisomerase I inhibitor. J Biol Chem 2014; 289:11374-11384. [PMID: 24573676 DOI: 10.1074/jbc.m113.531707] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The replication fork temporarily stalls when encountering an obstacle on the DNA, and replication resumes after the barrier is removed. Simultaneously, activation of the replication checkpoint delays the progression of S phase and inhibits late origin firing. Camptothecin (CPT), a topoisomerase I (Top1) inhibitor, acts as a DNA replication barrier by inducing the covalent retention of Top1 on DNA. The Timeless-Tipin complex, a component of the replication fork machinery, plays a role in replication checkpoint activation and stabilization of the replication fork. However, the role of the Timeless-Tipin complex in overcoming the CPT-induced replication block remains elusive. Here, we generated viable TIPIN gene knock-out (KO) DT40 cells showing delayed S phase progression and increased cell death. TIPIN KO cells were hypersensitive to CPT. However, homologous recombination and replication checkpoint were activated normally, whereas DNA synthesis activity was markedly decreased in CPT-treated TIPIN KO cells. Proteasome-dependent degradation of chromatin-bound Top1 was induced in TIPIN KO cells upon CPT treatment, and pretreatment with aphidicolin, a DNA polymerase inhibitor, suppressed both CPT sensitivity and Top1 degradation. Taken together, our data indicate that replication forks formed without Tipin may collide at a high rate with Top1 retained on DNA by CPT treatment, leading to CPT hypersensitivity and Top1 degradation in TIPIN KO cells.
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Affiliation(s)
- Yoshifumi Hosono
- Molecular Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Takuya Abe
- Instituto FIRC di Oncologia Molecolare (IFOM), Fondazione Italiana per la Ricerca sul Cancro (FIRC) Institute for Molecular Oncology Foundation, IFOM-Istituto Europeo di Oncologia Campus, Via Adamello 16, 20139 Milan, Italy
| | - Masato Higuchi
- Molecular Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Kosa Kajii
- Department of Biochemistry, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan
| | - Shuichi Sakuraba
- Molecular Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Shusuke Tada
- Faculty of Pharmaceutical Sciences, Teikyo Heisei University, 4-21-2 Nakano, Nakano-ku, Tokyo 164-8530, Japan, and
| | - Takemi Enomoto
- Molecular Cell Biology Laboratory, Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, 1-1-20 Shinmachi, Nishitokyo-shi, Tokyo 202-8585, Japan
| | - Masayuki Seki
- Department of Biochemistry, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981-8558, Japan,.
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