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Xu Y, Jiao Y, Liu C, Miao R, Liu C, Wang Y, Ma C, Liu J. R-loop and diseases: the cell cycle matters. Mol Cancer 2024; 23:84. [PMID: 38678239 PMCID: PMC11055327 DOI: 10.1186/s12943-024-02000-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2024] [Accepted: 04/13/2024] [Indexed: 04/29/2024] Open
Abstract
The cell cycle is a crucial biological process that is involved in cell growth, development, and reproduction. It can be divided into G1, S, G2, and M phases, and each period is closely regulated to ensure the production of two similar daughter cells with the same genetic material. However, many obstacles influence the cell cycle, including the R-loop that is formed throughout this process. R-loop is a triple-stranded structure, composed of an RNA: DNA hybrid and a single DNA strand, which is ubiquitous in organisms from bacteria to mammals. The existence of the R-loop has important significance for the regulation of various physiological processes. However, aberrant accumulation of R-loop due to its limited resolving ability will be detrimental for cells. For example, DNA damage and genomic instability, caused by the R-loop, can activate checkpoints in the cell cycle, which in turn induce cell cycle arrest and cell death. At present, a growing number of factors have been proven to prevent or eliminate the accumulation of R-loop thereby avoiding DNA damage and mutations. Therefore, we need to gain detailed insight into the R-loop resolution factors at different stages of the cell cycle. In this review, we review the current knowledge of factors that play a role in resolving the R-loop at different stages of the cell cycle, as well as how mutations of these factors lead to the onset and progression of diseases.
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Affiliation(s)
- Yuqin Xu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Yue Jiao
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chengbin Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Rui Miao
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chunyan Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Yilong Wang
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chunming Ma
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Jiao Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China.
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2
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Gambelli A, Ferrando A, Boncristiani C, Schoeftner S. Regulation and function of R-loops at repetitive elements. Biochimie 2023; 214:141-155. [PMID: 37619810 DOI: 10.1016/j.biochi.2023.08.013] [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: 05/05/2023] [Revised: 08/13/2023] [Accepted: 08/19/2023] [Indexed: 08/26/2023]
Abstract
R-loops are atypical, three-stranded nucleic acid structures that contain a stretch of RNA:DNA hybrids and an unpaired, single stranded DNA loop. R-loops are physiological relevant and can act as regulators of gene expression, chromatin structure, DNA damage repair and DNA replication. However, unscheduled and persistent R-loops are mutagenic and can mediate replication-transcription conflicts, leading to DNA damage and genome instability if left unchecked. Detailed transcriptome analysis unveiled that 85% of the human genome, including repetitive regions, hold transcriptional activity. This anticipates that R-loops management plays a central role for the regulation and integrity of genomes. This function is expected to have a particular relevance for repetitive sequences that make up to 75% of the human genome. Here, we review the impact of R-loops on the function and stability of repetitive regions such as centromeres, telomeres, rDNA arrays, transposable elements and triplet repeat expansions and discuss their relevance for associated pathological conditions.
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Affiliation(s)
- Alice Gambelli
- Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Via E. Weiss 2, 34127, Trieste, Italy
| | - Alessandro Ferrando
- Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Via E. Weiss 2, 34127, Trieste, Italy
| | - Chiara Boncristiani
- Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Via E. Weiss 2, 34127, Trieste, Italy
| | - Stefan Schoeftner
- Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Via E. Weiss 2, 34127, Trieste, Italy.
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Li F, Zafar A, Luo L, Denning AM, Gu J, Bennett A, Yuan F, Zhang Y. R-Loops in Genome Instability and Cancer. Cancers (Basel) 2023; 15:4986. [PMID: 37894353 PMCID: PMC10605827 DOI: 10.3390/cancers15204986] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 10/04/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023] Open
Abstract
R-loops are unique, three-stranded nucleic acid structures that primarily form when an RNA molecule displaces one DNA strand and anneals to the complementary DNA strand in a double-stranded DNA molecule. R-loop formation can occur during natural processes, such as transcription, in which the nascent RNA molecule remains hybridized with the template DNA strand, while the non-template DNA strand is displaced. However, R-loops can also arise due to many non-natural processes, including DNA damage, dysregulation of RNA degradation pathways, and defects in RNA processing. Despite their prevalence throughout the whole genome, R-loops are predominantly found in actively transcribed gene regions, enabling R-loops to serve seemingly controversial roles. On one hand, the pathological accumulation of R-loops contributes to genome instability, a hallmark of cancer development that plays a role in tumorigenesis, cancer progression, and therapeutic resistance. On the other hand, R-loops play critical roles in regulating essential processes, such as gene expression, chromatin organization, class-switch recombination, mitochondrial DNA replication, and DNA repair. In this review, we summarize discoveries related to the formation, suppression, and removal of R-loops and their influence on genome instability, DNA repair, and oncogenic events. We have also discussed therapeutical opportunities by targeting pathological R-loops.
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Affiliation(s)
- Fang Li
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Alyan Zafar
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Liang Luo
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Ariana Maria Denning
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Jun Gu
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Ansley Bennett
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Fenghua Yuan
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Yanbin Zhang
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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Liu C, Wang L, Li Y, Guo M, Hu J, Wang T, Li M, Yang Z, Lin R, Xu W, Chen Y, Luo M, Gao F, Chen JY, Sun Q, Liu H, Sun B, Li W. RNase H1 facilitates recombinase recruitment by degrading DNA-RNA hybrids during meiosis. Nucleic Acids Res 2023; 51:7357-7375. [PMID: 37378420 PMCID: PMC10415156 DOI: 10.1093/nar/gkad524] [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: 10/11/2022] [Revised: 05/29/2023] [Accepted: 06/05/2023] [Indexed: 06/29/2023] Open
Abstract
DNA-RNA hybrids play various roles in many physiological progresses, but how this chromatin structure is dynamically regulated during spermatogenesis remains largely unknown. Here, we show that germ cell-specific knockout of Rnaseh1, a specialized enzyme that degrades the RNA within DNA-RNA hybrids, impairs spermatogenesis and causes male infertility. Notably, Rnaseh1 knockout results in incomplete DNA repair and meiotic prophase I arrest. These defects arise from the altered RAD51 and DMC1 recruitment in zygotene spermatocytes. Furthermore, single-molecule experiments show that RNase H1 promotes recombinase recruitment to DNA by degrading RNA within DNA-RNA hybrids and allows nucleoprotein filaments formation. Overall, we uncover a function of RNase H1 in meiotic recombination, during which it processes DNA-RNA hybrids and facilitates recombinase recruitment.
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Affiliation(s)
- Chao Liu
- Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Stem Cell and Regenerative Medicine Innovation Institute, Chinese Academy of Sciences, Beijing 100101, China
| | - Liying Wang
- Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, China
| | - Yanan Li
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Mengmeng Guo
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Stem Cell and Regenerative Medicine Innovation Institute, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jun Hu
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing 210023, China
| | - Teng Wang
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Mengjing Li
- Center for Reproductive Medicine, Shandong University, Jinan 250012, China
| | - Zhuo Yang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ruoyao Lin
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing 210023, China
| | - Wei Xu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yinghong Chen
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Stem Cell and Regenerative Medicine Innovation Institute, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Mengcheng Luo
- Department of Tissue and Embryology, School of Basic Medical Sciences, Wuhan University, Hubei Provincial Key Laboratory of Developmentally Originated Disease, Wuhan 430072, China
| | - Fei Gao
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Stem Cell and Regenerative Medicine Innovation Institute, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jia-Yu Chen
- State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Chemistry and Biomedicine Innovation Center (ChemBIC), Nanjing University, Nanjing 210023, China
| | - Qianwen Sun
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
- Tsinghua-Peking Center for Life Sciences, Beijing 100084, China
| | - Hongbin Liu
- Center for Reproductive Medicine, Shandong University, Jinan 250012, China
| | - Bo Sun
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Wei Li
- Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou 510623, China
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Stem Cell and Regenerative Medicine Innovation Institute, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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Saha S, Pommier Y. R-loops, type I topoisomerases and cancer. NAR Cancer 2023; 5:zcad013. [PMID: 37600974 PMCID: PMC9984992 DOI: 10.1093/narcan/zcad013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/18/2023] [Accepted: 02/27/2023] [Indexed: 03/06/2023] Open
Abstract
R-loops are abundant and dynamic structures ubiquitously present in human cells both in the nuclear and mitochondrial genomes. They form in cis in the wake of transcription complexes and in trans apart from transcription complexes. In this review, we focus on the relationship between R-loops and topoisomerases, and cancer genomics and therapies. We summarize the topological parameters associated with the formation and resolution of R-loops, which absorb and release high levels of genomic negative supercoiling (Sc-). We review the deleterious consequences of excessive R-loops and rationalize how human type IA (TOP3B) and type IB (TOP1) topoisomerases regulate and resolve R-loops in coordination with helicase and RNase H enzymes. We also review the drugs (topoisomerase inhibitors, splicing inhibitors, G4 stabilizing ligands) and cancer predisposing genes (BRCA1/2, transcription, and splicing genes) known to induce R-loops, and whether stabilizing R-loops and thereby inducing genomic damage can be viewed as a strategy for cancer treatment.
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Affiliation(s)
- Sourav Saha
- Developmental Therapeutics Branch & Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Yves Pommier
- Developmental Therapeutics Branch & Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
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Khan ES, Danckwardt S. Pathophysiological Role and Diagnostic Potential of R-Loops in Cancer and Beyond. Genes (Basel) 2022; 13:genes13122181. [PMID: 36553448 PMCID: PMC9777984 DOI: 10.3390/genes13122181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/07/2022] [Accepted: 11/14/2022] [Indexed: 11/24/2022] Open
Abstract
R-loops are DNA-RNA hybrids that play multifunctional roles in gene regulation, including replication, transcription, transcription-replication collision, epigenetics, and preserving the integrity of the genome. The aberrant formation and accumulation of unscheduled R-loops can disrupt gene expression and damage DNA, thereby causing genome instability. Recent links between unscheduled R-loop accumulation and the abundance of proteins that modulate R-loop biogenesis have been associated with numerous human diseases, including various cancers. Although R-loops are not necessarily causative for all disease entities described to date, they can perpetuate and even exacerbate the initially disease-eliciting pathophysiology, making them structures of interest for molecular diagnostics. In this review, we discuss the (patho) physiological role of R-loops in health and disease, their surprising diagnostic potential, and state-of-the-art techniques for their detection.
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Affiliation(s)
- Essak S. Khan
- Posttranscriptional Gene Regulation, Cancer Research and Experimental Hemostasis, University Medical Center Mainz, 55131 Mainz, Germany
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- German Consortium for Translational Cancer Research (DKTK), DKFZ Frankfurt-Mainz, 60590 Frankfurt am Main, Germany
| | - Sven Danckwardt
- Posttranscriptional Gene Regulation, Cancer Research and Experimental Hemostasis, University Medical Center Mainz, 55131 Mainz, Germany
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- German Center for Cardiovascular Research (DZHK), Rhine-Main, 55131 Mainz, Germany
- Correspondence:
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Feng S, Manley JL. Beyond rRNA: nucleolar transcription generates a complex network of RNAs with multiple roles in maintaining cellular homeostasis. Genes Dev 2022; 36:876-886. [PMID: 36207140 PMCID: PMC9575697 DOI: 10.1101/gad.349969.122] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Nucleoli are the major cellular compartments for the synthesis of rRNA and assembly of ribosomes, the macromolecular complexes responsible for protein synthesis. Given the abundance of ribosomes, there is a huge demand for rRNA, which indeed constitutes ∼80% of the mass of RNA in the cell. Thus, nucleoli are characterized by extensive transcription of multiple rDNA loci by the dedicated polymerase, RNA polymerase (Pol) I. However, in addition to producing rRNAs, there is considerable additional transcription in nucleoli by RNA Pol II as well as Pol I, producing multiple noncoding (nc) and, in one instance, coding RNAs. In this review, we discuss important features of these transcripts, which often appear species-specific and reflect transcription antisense to pre-rRNA by Pol II and within the intergenic spacer regions on both strands by both Pol I and Pol II. We discuss how expression of these RNAs is regulated, their propensity to form cotranscriptional R loops, and how they modulate rRNA transcription, nucleolar structure, and cellular homeostasis more generally.
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Georgakopoulos-Soares I, Parada GE, Hemberg M. Secondary structures in RNA synthesis, splicing and translation. Comput Struct Biotechnol J 2022; 20:2871-2884. [PMID: 35765654 PMCID: PMC9198270 DOI: 10.1016/j.csbj.2022.05.041] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/19/2022] [Accepted: 05/21/2022] [Indexed: 11/30/2022] Open
Abstract
Even though the functional role of mRNA molecules is primarily decided by the nucleotide sequence, several properties are determined by secondary structure conformations. Examples of secondary structures include long range interactions, hairpins, R-loops and G-quadruplexes and they are formed through interactions of non-adjacent nucleotides. Here, we discuss advances in our understanding of how secondary structures can impact RNA synthesis, splicing, translation and mRNA half-life. During RNA synthesis, secondary structures determine RNA polymerase II (RNAPII) speed, thereby influencing splicing. Splicing is also determined by RNA binding proteins and their binding rates are modulated by secondary structures. For the initiation of translation, secondary structures can control the choice of translation start site. Here, we highlight the mechanisms by which secondary structures modulate these processes, discuss advances in technologies to detect and study them systematically, and consider the roles of RNA secondary structures in disease.
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