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Li Z, Wang Y. Short Double-Stranded DNA (≤40-bp) Affects Repair Pathway Choice. Int J Mol Sci 2023; 24:11836. [PMID: 37511594 PMCID: PMC10380458 DOI: 10.3390/ijms241411836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 07/11/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
To repair ionizing radiation (IR)-induced double strand breaks (DSBs), mammalian cells primarily use canonical non-homologous end-joining (cNHEJ), the homologous recombination (HR) pathway, and the alternative non-homologous end-joining (aEJ) as a backup. These pathways function either compensatively or competitively. High linear energy transfer (LET) compared to low-LET IR kills more cells at the same doses by inhibiting only cNHEJ, but not HR or aEJ. The mechanism remains unclear. The activation of each repair pathway requires the binding of different proteins to DNA fragments of varying lengths. We previously observed an increased generation of small DNA fragments (≤40 bp) in cells following high-LET IR compared to low-LET IR, suggesting that short DNA fragments were one of the major factors interfering with cNHEJ. To provide direct evidence, here we compare the efficiencies of cNHEJ, HR, or aEJ in repairing DSBs containing 30- or 60-bp fragments in vitro and in cells. We show that only cNHEJ but not HR or a-EJ was inefficient for repairing DSBs with 30-bp fragments compared to 60-bp ones, which strongly supports our hypothesis. These results not only enhance our understanding of the DSB repair pathway choice but also hold potential benefits for protection against high-LET IR-induced damage or improving high-LET radiotherapy.
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Affiliation(s)
- Zhentian Li
- Department of Radiation Oncology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Ya Wang
- Department of Radiation Oncology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 30322, USA
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Disruption of Chromatin Dynamics by Hypotonic Stress Suppresses HR and Shifts DSB Processing to Error-Prone SSA. Int J Mol Sci 2021; 22:ijms222010957. [PMID: 34681628 PMCID: PMC8535785 DOI: 10.3390/ijms222010957] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 10/04/2021] [Accepted: 10/05/2021] [Indexed: 11/17/2022] Open
Abstract
The processing of DNA double-strand breaks (DSBs) depends on the dynamic characteristics of chromatin. To investigate how abrupt changes in chromatin compaction alter these dynamics and affect DSB processing and repair, we exposed irradiated cells to hypotonic stress (HypoS). Densitometric and chromosome-length analyses show that HypoS transiently decompacts chromatin without inducing histone modifications known from regulated local chromatin decondensation, or changes in Micrococcal Nuclease (MNase) sensitivity. HypoS leaves undisturbed initial stages of DNA-damage-response (DDR), such as radiation-induced ATM activation and H2AX-phosphorylation. However, detection of ATM-pS1981, γ-H2AX and 53BP1 foci is reduced in a protein, cell cycle phase and cell line dependent manner; likely secondary to chromatin decompaction that disrupts the focal organization of DDR proteins. While HypoS only exerts small effects on classical nonhomologous end-joining (c-NHEJ) and alternative end-joining (alt-EJ), it markedly suppresses homologous recombination (HR) without affecting DNA end-resection at DSBs, and clearly enhances single-strand annealing (SSA). These shifts in pathway engagement are accompanied by decreases in HR-dependent chromatid-break repair in the G2-phase, and by increases in alt-EJ and SSA-dependent chromosomal translocations. Consequently, HypoS sensitizes cells to ionizing radiation (IR)-induced killing. We conclude that HypoS-induced global chromatin decompaction compromises regulated chromatin dynamics and genomic stability by suppressing DSB-processing by HR, and allowing error-prone processing by alt-EJ and SSA.
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Muvarak NE, Chowdhury K, Xia L, Robert C, Choi EY, Cai Y, Bellani M, Zou Y, Singh ZN, Duong VH, Rutherford T, Nagaria P, Bentzen SM, Seidman MM, Baer MR, Lapidus RG, Baylin SB, Rassool FV. Enhancing the Cytotoxic Effects of PARP Inhibitors with DNA Demethylating Agents - A Potential Therapy for Cancer. Cancer Cell 2016; 30:637-650. [PMID: 27728808 PMCID: PMC5201166 DOI: 10.1016/j.ccell.2016.09.002] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 03/16/2016] [Accepted: 09/08/2016] [Indexed: 12/20/2022]
Abstract
Poly (ADP-ribose) polymerase inhibitors (PARPis) are clinically effective predominantly for BRCA-mutant tumors. We introduce a mechanism-based strategy to enhance PARPi efficacy based on DNA damage-related binding between DNA methyltransferases (DNMTs) and PARP1. In acute myeloid leukemia (AML) and breast cancer cells, DNMT inhibitors (DNMTis) alone covalently bind DNMTs into DNA and increase PARP1 tightly bound into chromatin. Low doses of DNMTis plus PARPis, versus each drug alone, increase PARPi efficacy, increasing amplitude and retention of PARP1 directly at laser-induced DNA damage sites. This correlates with increased DNA damage, synergistic tumor cytotoxicity, blunting of self-renewal, and strong anti-tumor responses, in vivo in unfavorable AML subtypes and BRCA wild-type breast cancer cells. Our combinatorial approach introduces a strategy to enhance efficacy of PARPis in treating cancer.
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MESH Headings
- Animals
- Antineoplastic Combined Chemotherapy Protocols/pharmacology
- Cell Line, Tumor
- Chromatin/metabolism
- DNA Breaks, Double-Stranded
- DNA Methylation/drug effects
- Drug Synergism
- Female
- Humans
- Leukemia, Myeloid, Acute/drug therapy
- Leukemia, Myeloid, Acute/genetics
- Leukemia, Myeloid, Acute/metabolism
- Male
- Mice
- Mice, Inbred NOD
- Mice, Nude
- Phthalazines/pharmacology
- Poly (ADP-Ribose) Polymerase-1/antagonists & inhibitors
- Poly (ADP-Ribose) Polymerase-1/metabolism
- Poly(ADP-ribose) Polymerase Inhibitors/pharmacology
- Triple Negative Breast Neoplasms/drug therapy
- Triple Negative Breast Neoplasms/genetics
- Triple Negative Breast Neoplasms/metabolism
- Xenograft Model Antitumor Assays
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Affiliation(s)
- Nidal E Muvarak
- Department of Radiation Oncology, University of Maryland, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA
| | - Khadiza Chowdhury
- Department of Radiation Oncology, University of Maryland, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA
| | - Limin Xia
- The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Medical Institutions, Baltimore, MD 21231, USA
| | - Carine Robert
- Department of Radiation Oncology, University of Maryland, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA
| | - Eun Yong Choi
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA
| | - Yi Cai
- The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Medical Institutions, Baltimore, MD 21231, USA
| | - Marina Bellani
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD 21224, USA
| | - Ying Zou
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Zeba N Singh
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Vu H Duong
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA
| | | | - Pratik Nagaria
- Department of Radiation Oncology, University of Maryland, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA
| | - Søren M Bentzen
- Department of Radiation Oncology, University of Maryland, Baltimore, MD 21201, USA; Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Michael M Seidman
- Laboratory of Molecular Gerontology, National Institute on Aging, Baltimore, MD 21224, USA
| | - Maria R Baer
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA; Veterans Affairs Medical Center, Baltimore, MD 21201, USA
| | - Rena G Lapidus
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA
| | - Stephen B Baylin
- The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Medical Institutions, Baltimore, MD 21231, USA; Van Andel Research Institute, Grand Rapids, MI 49503
| | - Feyruz V Rassool
- Department of Radiation Oncology, University of Maryland, Baltimore, MD 21201, USA; University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, MD 21201, USA.
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Lavelle C, Foray N. Chromatin structure and radiation-induced DNA damage: from structural biology to radiobiology. Int J Biochem Cell Biol 2014; 49:84-97. [PMID: 24486235 DOI: 10.1016/j.biocel.2014.01.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 01/13/2014] [Accepted: 01/18/2014] [Indexed: 10/25/2022]
Abstract
Genomic DNA in eukaryotic cells is basically divided into chromosomes, each consisting of a single huge nucleosomal fiber. It is now clear that chromatin structure and dynamics play a critical role in all processes involved in DNA metabolism, e.g. replication, transcription, repair and recombination. Radiation is a useful tool to study the biological effects of chromatin alterations. Conversely, radiotherapy and radiodiagnosis raise questions about the influence of chromatin integrity on clinical features and secondary effects. This review focuses on the link between DNA damage and chromatin structure at different scales, showing how a comprehensive multiscale vision is required to understand better the effect of radiations on DNA. Clinical aspects related to high- and low-dose of radiation and chromosomal instability will be discussed. At the same time, we will show that the analysis of the radiation-induced DNA damage distribution provides good insight on chromatin structure. Hence, we argue that chromatin "structuralists" and radiobiological "clinicians" would each benefit from more collaboration with the other. We hope that this focused review will help in this regard.
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Affiliation(s)
- Christophe Lavelle
- Genome Structure and Instability, National Museum of Natural History, Paris, France; CNRS UMR7196, Paris, France; INSERM U1154, Paris, France; Nuclear Architecture and Dynamics, CNRS GDR 3536, Paris, France.
| | - Nicolas Foray
- Nuclear Architecture and Dynamics, CNRS GDR 3536, Paris, France; INSERM, UMR1052, Radiobiology Group, Cancer Research Centre of Lyon, Lyon, France
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