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Kojima K, Ohkubo H, Kawasumi R, Hirota K. Pold4 subunit of replicative polymerase δ promotes fork slowing at broken templates. DNA Repair (Amst) 2024; 139:103688. [PMID: 38678695 DOI: 10.1016/j.dnarep.2024.103688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 02/25/2024] [Accepted: 04/23/2024] [Indexed: 05/01/2024]
Abstract
Single-strand breaks (SSBs) are the most frequent type of lesion, and replication across such lesions leads to double-strand breaks (DSBs). DSBs that arise during replication are repaired by homologous recombination (HR) and are suppressed by fork reversal. Poly[ADP-ribose] polymerase I (PARP1) and the proofreading exonuclease activity of replicative polymerase ε (Polε) are required for fork reversal when leading strand replication encounters SSBs. However, the mechanism underlying fork reversal at the SSB during lagging-strand replication remains elusive. We here demonstrate that the Pold4 subunit of replicative polymerase δ (Polδ) plays a role in promoting fork reversal during lagging strand replication on a broken template. POLD4-/- cells exhibited heightened sensitivity to camptothecin (CPT) but not to other DNA-damaging agents compared to wild-type cells. This selective CPT sensitivity in POLD4-/- cells suggests that Pold4 suppresses DSBs during replication, as CPT induces significant SSBs during replication, which subsequently lead to DSBs. To explore the functional interactions among Pold4, Polε exonuclease, and PARP1 in DSB suppression, we generated PARP1-/-, POLD4-/-, Polε exonuclease-deficient POLE1exo-/-, PARP1-/-/POLD4-/-, and POLD4-/-/POLE1exo-/- cells. These epistasis analyses showed that Pold4 is involved in the PARP1-Polε exonuclease-mediated fork reversal following CPT treatment. These results suggest that Pold4 aids in fork reversal when lagging strand replication stalls on a broken template. In conclusion, the Pold4 subunit of Polδ has roles in the PARP1-Polε exonuclease-mediated fork reversal, contributing to the suppression of DSBs.
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Affiliation(s)
- Kota Kojima
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Hiromori Ohkubo
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Ryotaro Kawasumi
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Kouji Hirota
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan.
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Hosen MB, Kawasumi R, Hirota K. Dominant roles of BRCA1 in cellular tolerance to a chain-terminating nucleoside analog, alovudine. DNA Repair (Amst) 2024; 137:103668. [PMID: 38460389 DOI: 10.1016/j.dnarep.2024.103668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Revised: 02/28/2024] [Accepted: 03/01/2024] [Indexed: 03/11/2024]
Abstract
Alovudine is a chain-terminating nucleoside analog (CTNA) that is frequently used as an antiviral and anticancer agent. Generally, CTNAs inhibit DNA replication after their incorporation into nascent DNA during DNA synthesis by suppressing subsequent polymerization, which restricts the proliferation of viruses and cancer cells. Alovudine is a thymidine analog used as an antiviral drug. However, the mechanisms underlying the removal of alovudine and DNA damage tolerance pathways involved in cellular resistance to alovudine remain unclear. Here, we explored the DNA damage tolerance pathways responsible for cellular tolerance to alovudine and found that BRCA1-deficient cells exhibited the highest sensitivity to alovudine. Moreover, alovudine interfered with DNA replication in two distinct mechanisms: first: alovudine incorporated at the end of nascent DNA interfered with subsequent DNA synthesis; second: DNA replication stalled on the alovudine-incorporated template strand. Additionally, BRCA1 facilitated the removal of the incorporated alovudine from nascent DNA, and BRCA1-mediated homologous recombination (HR) contributed to the progressive replication on the alovudine-incorporated template. Thus, we have elucidated the previously unappreciated mechanism of alovudine-mediated inhibition of DNA replication and the role of BRCA1 in cellular tolerance to alovudine.
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Affiliation(s)
- Md Bayejid Hosen
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Ryotaro Kawasumi
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan
| | - Kouji Hirota
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan.
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Mellor C, Nassar J, Šviković S, Sale J. PRIMPOL ensures robust handoff between on-the-fly and post-replicative DNA lesion bypass. Nucleic Acids Res 2024; 52:243-258. [PMID: 37971291 PMCID: PMC10783524 DOI: 10.1093/nar/gkad1054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 10/17/2023] [Accepted: 10/24/2023] [Indexed: 11/19/2023] Open
Abstract
The primase/polymerase PRIMPOL restarts DNA synthesis when replication is arrested by template impediments. However, we do not have a comprehensive view of how PRIMPOL-dependent repriming integrates with the main pathways of damage tolerance, REV1-dependent 'on-the-fly' lesion bypass at the fork and PCNA ubiquitination-dependent post-replicative gap filling. Guided by genome-wide CRISPR/Cas9 screens to survey the genetic interactions of PRIMPOL in a non-transformed and p53-proficient human cell line, we find that PRIMPOL is needed for cell survival following loss of the Y-family polymerases REV1 and POLη in a lesion-dependent manner, while it plays a broader role in promoting survival of cells lacking PCNA K164-dependent post-replicative gap filling. Thus, while REV1- and PCNA K164R-bypass provide two layers of protection to ensure effective damage tolerance, PRIMPOL is required to maximise the effectiveness of the interaction between them. We propose this is through the restriction of post-replicative gap length provided by PRIMPOL-dependent repriming.
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Affiliation(s)
- Christopher Mellor
- Division of Protein & Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Joelle Nassar
- Division of Protein & Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Saša Šviković
- Division of Protein & Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Julian E Sale
- Division of Protein & Nucleic Acid Chemistry, Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
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Das D, Duncton MAJ, Georgiadis TM, Pellicena P, Clark J, Sobol RW, Georgiadis MM, King-Underwood J, Jobes DV, Chang C, Gao Y, Deacon AM, Wilson DM. A New Drug Discovery Platform: Application to DNA Polymerase Eta and Apurinic/Apyrimidinic Endonuclease 1. Int J Mol Sci 2023; 24:16637. [PMID: 38068959 PMCID: PMC10706420 DOI: 10.3390/ijms242316637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/26/2023] [Accepted: 10/27/2023] [Indexed: 12/18/2023] Open
Abstract
The ability to quickly discover reliable hits from screening and rapidly convert them into lead compounds, which can be verified in functional assays, is central to drug discovery. The expedited validation of novel targets and the identification of modulators to advance to preclinical studies can significantly increase drug development success. Our SaXPyTM ("SAR by X-ray Poses Quickly") platform, which is applicable to any X-ray crystallography-enabled drug target, couples the established methods of protein X-ray crystallography and fragment-based drug discovery (FBDD) with advanced computational and medicinal chemistry to deliver small molecule modulators or targeted protein degradation ligands in a short timeframe. Our approach, especially for elusive or "undruggable" targets, allows for (i) hit generation; (ii) the mapping of protein-ligand interactions; (iii) the assessment of target ligandability; (iv) the discovery of novel and potential allosteric binding sites; and (v) hit-to-lead execution. These advances inform chemical tractability and downstream biology and generate novel intellectual property. We describe here the application of SaXPy in the discovery and development of DNA damage response inhibitors against DNA polymerase eta (Pol η or POLH) and apurinic/apyrimidinic endonuclease 1 (APE1 or APEX1). Notably, our SaXPy platform allowed us to solve the first crystal structures of these proteins bound to small molecules and to discover novel binding sites for each target.
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Affiliation(s)
- Debanu Das
- XPose Therapeutics, Inc., San Carlos, CA 94070, USA
- Accelero Biostructures, Inc., San Carlos, CA 94070, USA
| | | | | | | | - Jennifer Clark
- Mitchell Cancer Institute and Department of Pharmacology, University of South Alabama, Mobile, AL 36604, USA
| | - Robert W. Sobol
- Mitchell Cancer Institute and Department of Pharmacology, University of South Alabama, Mobile, AL 36604, USA
- Department of Pathology & Laboratory Medicine, Warrant Alpert Medical School & Legorreta Cancer Center, Brown University, Providence, RI 02912, USA
| | - Millie M. Georgiadis
- XPose Therapeutics, Inc., San Carlos, CA 94070, USA
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | | | - David V. Jobes
- XPose Therapeutics, Inc., San Carlos, CA 94070, USA
- Mid-Atlantic BioTherapeutics, Inc., Doylestown, PA 18902, USA
| | - Caleb Chang
- Department of BioSciences, Rice University, Houston, TX 77251, USA
| | - Yang Gao
- Department of BioSciences, Rice University, Houston, TX 77251, USA
| | - Ashley M. Deacon
- XPose Therapeutics, Inc., San Carlos, CA 94070, USA
- Accelero Biostructures, Inc., San Carlos, CA 94070, USA
| | - David M. Wilson
- XPose Therapeutics, Inc., San Carlos, CA 94070, USA
- Biomedical Research Institute, Hasselt University, 3500 Diepenbeek, Belgium
- Belgium & Boost Scientific, 3550 Heusden-Zolder, Belgium
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Joseph AM, Nahar K, Daw S, Hasan MM, Lo R, Le TBK, Rahman KM, Badrinarayanan A. Mechanistic insight into the repair of C8-linked pyrrolobenzodiazepine monomer-mediated DNA damage. RSC Med Chem 2022; 13:1621-1633. [PMID: 36561066 PMCID: PMC9749960 DOI: 10.1039/d2md00194b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 10/18/2022] [Indexed: 11/07/2022] Open
Abstract
Pyrrolobenzodiazepines (PBDs) are naturally occurring DNA binding compounds that possess anti-tumor and anti-bacterial activity. Chemical modifications of PBDs can result in improved DNA binding, sequence specificity and enhanced efficacy. More recently, synthetic PBD monomers have shown promise as payloads for antibody drug conjugates and anti-bacterial agents. The precise mechanism of action of these PBD monomers and their role in causing DNA damage remains to be elucidated. Here we characterized the damage-inducing potential of two C8-linked PBD bi-aryl monomers in Caulobacter crescentus and investigated the strategies employed by cells to repair the same. We show that these compounds cause DNA damage and efficiently kill bacteria, in a manner comparable to the extensively used DNA cross-linking agent mitomycin-C (MMC). However, in stark contrast to MMC which employs a mutagenic lesion tolerance pathway, we implicate essential functions for error-free mechanisms in repairing PBD monomer-mediated damage. We find that survival is severely compromised in cells lacking nucleotide excision repair and to a lesser extent, in cells with impaired recombination-based repair. Loss of nucleotide excision repair leads to significant increase in double-strand breaks, underscoring the critical role of this pathway in mediating repair of PBD-induced DNA lesions. Together, our study provides comprehensive insights into how mono-alkylating DNA-targeting therapeutic compounds like PBD monomers challenge cell growth, and identifies the specific mechanisms employed by the cell to counter the same.
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Affiliation(s)
- Asha Mary Joseph
- National Centre for Biological Sciences (Tata Institute of Fundamental Research) Bangalore India
| | - Kazi Nahar
- School of Cancer & Pharmaceutical Sciences, Faculty of Life Sciences & Medicine, King's College London Franklin-Wilkins Building, 150 Stamford Street London SE1 9NH UK
| | - Saheli Daw
- National Centre for Biological Sciences (Tata Institute of Fundamental Research) Bangalore India
| | - Md Mahbub Hasan
- School of Cancer & Pharmaceutical Sciences, Faculty of Life Sciences & Medicine, King's College London Franklin-Wilkins Building, 150 Stamford Street London SE1 9NH UK
| | - Rebecca Lo
- John Innes Centre, Department of Molecular Microbiology Colney Lane Norwich NR4 7UH UK
| | - Tung B K Le
- John Innes Centre, Department of Molecular Microbiology Colney Lane Norwich NR4 7UH UK
| | - Khondaker Miraz Rahman
- School of Cancer & Pharmaceutical Sciences, Faculty of Life Sciences & Medicine, King's College London Franklin-Wilkins Building, 150 Stamford Street London SE1 9NH UK
| | - Anjana Badrinarayanan
- National Centre for Biological Sciences (Tata Institute of Fundamental Research) Bangalore India
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Kaszubowski JD, Trakselis MA. Beyond the Lesion: Back to High Fidelity DNA Synthesis. Front Mol Biosci 2022; 8:811540. [PMID: 35071328 PMCID: PMC8766770 DOI: 10.3389/fmolb.2021.811540] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 12/16/2021] [Indexed: 12/16/2022] Open
Abstract
High fidelity (HiFi) DNA polymerases (Pols) perform the bulk of DNA synthesis required to duplicate genomes in all forms of life. Their structural features, enzymatic mechanisms, and inherent properties are well-described over several decades of research. HiFi Pols are so accurate that they become stalled at sites of DNA damage or lesions that are not one of the four canonical DNA bases. Once stalled, the replisome becomes compromised and vulnerable to further DNA damage. One mechanism to relieve stalling is to recruit a translesion synthesis (TLS) Pol to rapidly synthesize over and past the damage. These TLS Pols have good specificities for the lesion but are less accurate when synthesizing opposite undamaged DNA, and so, mechanisms are needed to limit TLS Pol synthesis and recruit back a HiFi Pol to reestablish the replisome. The overall TLS process can be complicated with several cellular Pols, multifaceted protein contacts, and variable nucleotide incorporation kinetics all contributing to several discrete substitution (or template hand-off) steps. In this review, we highlight the mechanistic differences between distributive equilibrium exchange events and concerted contact-dependent switching by DNA Pols for insertion, extension, and resumption of high-fidelity synthesis beyond the lesion.
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