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Miller HE, Montemayor D, Levy S, Sharma K, Frost B, Bishop AJR. RLSuite: An Integrative R-Loop Bioinformatics Framework. JOURNAL OF BIOINFORMATICS AND SYSTEMS BIOLOGY : OPEN ACCESS 2023; 6:364-378. [PMID: 38292828 PMCID: PMC10827345 DOI: 10.26502/jbsb.5107071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
We recently described the development of a database of 810 R-loop mapping datasets and used this data to conduct a meta-analysis of R-loops. R-loops are three-stranded nucleic acid structures containing RNA:DNA hybrids and we were able to verify that 30% of expressed genes have an associated R-loop in a location conserved manner.. Moreover, intergenic R-loops map to enhancers, super enhancers and with TAD domain boundaries. This work demonstrated that R-loop mapping via high-throughput sequencing can reveal novel insight into R-loop biology, however the analysis and quality control of these data is a non-trivial task for which few bioinformatic tools exist. Herein we describe RLSuite, an integrative R-loop bioinformatics framework for pre-processing, quality control, and downstream analysis of R-loop mapping data. RLSuite enables users to compare their data to hundreds of public datasets and generate a user-friendly analysis report for sharing with non-bioinformatician colleagues. Taken together, RLSuite is a novel analysis framework that should greatly benefit the emerging R-loop bioinformatics community in a rapidly expanding aspect of epigenetic control that is still poorly understood.
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Affiliation(s)
- H E Miller
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA
- Greehey Children's Cancer Research Institute, UT Health San Antonio, San Antonio, TX, USA
- Bioinformatics Research Network, Atlanta, GA, USA
| | - D Montemayor
- Department of Medicine, UT Health San Antonio, San Antonio, TX, USA
- Center for Precision Medicine, UT Health San Antonio, San Antonio, TX, USA
| | - S Levy
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA
- Bioinformatics Research Network, Atlanta, GA, USA
- Sam & Ann Barshop Institute for Longevity & Aging Studies, UT Health San Antonio, San Antonio, TX, USA
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, UT Health San Antonio, San Antonio, TX, USA
| | - K Sharma
- Department of Medicine, UT Health San Antonio, San Antonio, TX, USA
- Center for Precision Medicine, UT Health San Antonio, San Antonio, TX, USA
| | - B Frost
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA
- Sam & Ann Barshop Institute for Longevity & Aging Studies, UT Health San Antonio, San Antonio, TX, USA
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, UT Health San Antonio, San Antonio, TX, USA
| | - A J R Bishop
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA
- Greehey Children's Cancer Research Institute, UT Health San Antonio, San Antonio, TX, USA
- May's Cancer Center, UT Health San Antonio, San Antonio, TX, USA
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2
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Papp C, Mukundan VT, Jenjaroenpun P, Winnerdy FR, Ow GS, Phan AT, Kuznetsov VA. Stable bulged G-quadruplexes in the human genome: identification, experimental validation and functionalization. Nucleic Acids Res 2023; 51:4148-4177. [PMID: 37094040 DOI: 10.1093/nar/gkad252] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 03/23/2023] [Accepted: 04/19/2023] [Indexed: 04/26/2023] Open
Abstract
DNA sequence composition determines the topology and stability of G-quadruplexes (G4s). Bulged G-quadruplex structures (G4-Bs) are a subset of G4s characterized by 3D conformations with bulges. Current search algorithms fail to capture stable G4-B, making their genome-wide study infeasible. Here, we introduced a large family of computationally defined and experimentally verified potential G4-B forming sequences (pG4-BS). We found 478 263 pG4-BS regions that do not overlap 'canonical' G4-forming sequences in the human genome and are preferentially localized in transcription regulatory regions including R-loops and open chromatin. Over 90% of protein-coding genes contain pG4-BS in their promoter or gene body. We observed generally higher pG4-BS content in R-loops and their flanks, longer genes that are associated with brain tissue, immune and developmental processes. Also, the presence of pG4-BS on both template and non-template strands in promoters is associated with oncogenesis, cardiovascular disease and stemness. Our G4-BS models predicted G4-forming ability in vitro with 91.5% accuracy. Analysis of G4-seq and CUT&Tag data strongly supports the existence of G4-BS conformations genome-wide. We reconstructed a novel G4-B 3D structure located in the E2F8 promoter. This study defines a large family of G4-like sequences, offering new insights into the essential biological functions and potential future therapeutic uses of G4-B.
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Affiliation(s)
- Csaba Papp
- Department of Urology, Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Vineeth T Mukundan
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Piroon Jenjaroenpun
- Division of Bioinformatics and Data Management for Research, Research Group and Research Network Division, Research Department, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
- Bioinformatics Institute, A*STAR Biomedical Institutes, Singapore, Singapore
| | - Fernaldo Richtia Winnerdy
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Ghim Siong Ow
- Bioinformatics Institute, A*STAR Biomedical Institutes, Singapore, Singapore
| | - Anh Tuân Phan
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
- NTU Institute of Structural Biology, Nanyang Technological University, Singapore 636921, Singapore
| | - Vladimir A Kuznetsov
- Department of Urology, Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
- Bioinformatics Institute, A*STAR Biomedical Institutes, Singapore, Singapore
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3
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Stefos GC, Theodorou G, Politis I. Genomic distribution and polymorphism of G-quadruplex motifs occupying ovine promoters and enhancers. Mamm Genome 2023:10.1007/s00335-023-09988-x. [PMID: 36964238 PMCID: PMC10382345 DOI: 10.1007/s00335-023-09988-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 03/10/2023] [Indexed: 03/26/2023]
Abstract
G-quadruplexes are non-canonical DNA structures that are formed in regions with short runs of guanines. During the last decade they have gained considerable attention due to their involvement in basic cellular processes, linking them to several physiological processes and pathological conditions. Regulation of gene transcription is among the crucial roles that G-quadruplexes play in the cells. Several ways in which these structures affect transcription have been described, both negatively and positively. Recently, G-quadruplexes have been shown to be implicated in the three-dimensional rearrangement of the chromosomes that enables the interaction of enhancers and gene promoters during regulation of transcription. Sheep is a species for which almost no G-quadruplex-related studies have been conducted and thus research on this species is kept out from the progress that has been made in the G-quadruplex field. In this context, we investigated the DNA sequences with potential to form G-quadruplexes (G4-motifs) in the ovine enhancers and promoters. We describe the distribution of G4-motifs within the regulatory regions which is shown to be enriched in G4-motifs in a way similar to other mammals. Furthermore, our data suggest that G4-motifs promote promoter-enhancer interactions in sheep. The single nucleotide polymorphisms colocalizing with promoter- and enhancer-associated ovine G4-motifs constitute a considerable pool of polymorphism and given the crucial role of these specific G4-motifs on regulation of transcription, we suggest this polymorphism as an interesting target for ovine genetic studies.
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Affiliation(s)
- Georgios C Stefos
- Laboratory of Animal Breeding and Husbandry, Department of Animal Science, Agricultural University of Athens, 75 Iera Odos, 118 55, Athens, Greece.
| | - Georgios Theodorou
- Laboratory of Animal Breeding and Husbandry, Department of Animal Science, Agricultural University of Athens, 75 Iera Odos, 118 55, Athens, Greece.
| | - Ioannis Politis
- Laboratory of Animal Breeding and Husbandry, Department of Animal Science, Agricultural University of Athens, 75 Iera Odos, 118 55, Athens, Greece
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4
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Tang J, Wang X, Xiao D, Liu S, Tao Y. The chromatin-associated RNAs in gene regulation and cancer. Mol Cancer 2023; 22:27. [PMID: 36750826 PMCID: PMC9903551 DOI: 10.1186/s12943-023-01724-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 01/16/2023] [Indexed: 02/09/2023] Open
Abstract
Eukaryotic genomes are prevalently transcribed into many types of RNAs that translate into proteins or execute gene regulatory functions. Many RNAs associate with chromatin directly or indirectly and are called chromatin-associated RNAs (caRNAs). To date, caRNAs have been found to be involved in gene and transcriptional regulation through multiple mechanisms and have important roles in different types of cancers. In this review, we first present different categories of caRNAs and the modes of interaction between caRNAs and chromatin. We then detail the mechanisms of chromatin-associated nascent RNAs, chromatin-associated noncoding RNAs and emerging m6A on caRNAs in transcription and gene regulation. Finally, we discuss the roles of caRNAs in cancer as well as epigenetic and epitranscriptomic mechanisms contributing to cancer, which could provide insights into the relationship between different caRNAs and cancer, as well as tumor treatment and intervention.
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Affiliation(s)
- Jun Tang
- grid.216417.70000 0001 0379 7164Hunan Key Laboratory of Cancer Metabolism, Hunan Cancer Hospital and The Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, 410078 Hunan China ,grid.216417.70000 0001 0379 7164Key Laboratory of Carcinogenesis and Cancer Invasion (Ministry of Education), NHC Key Laboratory of Carcinogenesis (Central South University), Cancer Research Institute and School of Basic Medicine, Central South University, Changsha, 410078 Hunan China
| | - Xiang Wang
- grid.216417.70000 0001 0379 7164Department of Thoracic Surgery, Hunan Key Laboratory of Early Diagnosis and Precision Therapy in Lung Cancer, Second Xiangya Hospital, Central South University, Changsha, 410011 China
| | - Desheng Xiao
- Department of Pathology, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China.
| | - Shuang Liu
- Department of Oncology, Institute of Medical Sciences, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China.
| | - Yongguang Tao
- Hunan Key Laboratory of Cancer Metabolism, Hunan Cancer Hospital and The Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, 410078, Hunan, China. .,Key Laboratory of Carcinogenesis and Cancer Invasion (Ministry of Education), NHC Key Laboratory of Carcinogenesis (Central South University), Cancer Research Institute and School of Basic Medicine, Central South University, Changsha, 410078, Hunan, China. .,Department of Thoracic Surgery, Hunan Key Laboratory of Early Diagnosis and Precision Therapy in Lung Cancer, Second Xiangya Hospital, Central South University, Changsha, 410011, China. .,Department of Pathology, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China.
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5
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Fan C, Chen K, Wang Y, Ball EV, Stenson PD, Mort M, Bacolla A, Kehrer-Sawatzki H, Tainer JA, Cooper DN, Zhao H. Profiling human pathogenic repeat expansion regions by synergistic and multi-level impacts on molecular connections. Hum Genet 2023; 142:245-274. [PMID: 36344696 PMCID: PMC10290229 DOI: 10.1007/s00439-022-02500-6] [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: 08/02/2022] [Accepted: 10/24/2022] [Indexed: 11/09/2022]
Abstract
Whilst DNA repeat expansions cause numerous heritable human disorders, their origins and underlying pathological mechanisms are often unclear. We collated a dataset comprising 224 human repeat expansions encompassing 203 different genes, and performed a systematic analysis with respect to key topological features at the DNA, RNA and protein levels. Comparison with controls without known pathogenicity and genomic regions lacking repeats, allowed the construction of the first tool to discriminate repeat regions harboring pathogenic repeat expansions (DPREx). At the DNA level, pathogenic repeat expansions exhibited stronger signals for DNA regulatory factors (e.g. H3K4me3, transcription factor-binding sites) in exons, promoters, 5'UTRs and 5'genes but were not significantly different from controls in introns, 3'UTRs and 3'genes. Additionally, pathogenic repeat expansions were also found to be enriched in non-B DNA structures. At the RNA level, pathogenic repeat expansions were characterized by lower free energy for forming RNA secondary structure and were closer to splice sites in introns, exons, promoters and 5'genes than controls. At the protein level, pathogenic repeat expansions exhibited a preference to form coil rather than other types of secondary structure, and tended to encode surface-located protein domains. Guided by these features, DPREx ( http://biomed.nscc-gz.cn/zhaolab/geneprediction/# ) achieved an Area Under the Curve (AUC) value of 0.88 in a test on an independent dataset. Pathogenic repeat expansions are thus located such that they exert a synergistic influence on the gene expression pathway involving inter-molecular connections at the DNA, RNA and protein levels.
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Affiliation(s)
- Cong Fan
- Department of Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, 107 Yan Jiang West Road, Guangzhou, 500001, People's Republic of China
| | - Ken Chen
- School of Computer Science and Engineering, Sun Yat-Sen University, Guangzhou, 500001, China
| | - Yukai Wang
- School of Life Science, Sun Yat-Sen University, Guangzhou, 500001, China
| | - Edward V Ball
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
| | - Peter D Stenson
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
| | - Matthew Mort
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
| | - Albino Bacolla
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, 6767 Bertner Avenue, Houston, TX, 77030, USA
| | | | - John A Tainer
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, 6767 Bertner Avenue, Houston, TX, 77030, USA
| | - David N Cooper
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
| | - Huiying Zhao
- Department of Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, 107 Yan Jiang West Road, Guangzhou, 500001, People's Republic of China.
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6
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Shi X, Teng H, Sun Z. An updated overview of experimental and computational approaches to identify non-canonical DNA/RNA structures with emphasis on G-quadruplexes and R-loops. Brief Bioinform 2022; 23:bbac441. [PMID: 36208174 PMCID: PMC9677470 DOI: 10.1093/bib/bbac441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 08/22/2022] [Accepted: 09/13/2022] [Indexed: 12/14/2022] Open
Abstract
Multiple types of non-canonical nucleic acid structures play essential roles in DNA recombination and replication, transcription, and genomic instability and have been associated with several human diseases. Thus, an increasing number of experimental and bioinformatics methods have been developed to identify these structures. To date, most reviews have focused on the features of non-canonical DNA/RNA structure formation, experimental approaches to mapping these structures, and the association of these structures with diseases. In addition, two reviews of computational algorithms for the prediction of non-canonical nucleic acid structures have been published. One of these reviews focused only on computational approaches for G4 detection until 2020. The other mainly summarized the computational tools for predicting cruciform, H-DNA and Z-DNA, in which the algorithms discussed were published before 2012. Since then, several experimental and computational methods have been developed. However, a systematic review including the conformation, sequencing mapping methods and computational prediction strategies for these structures has not yet been published. The purpose of this review is to provide an updated overview of conformation, current sequencing technologies and computational identification methods for non-canonical nucleic acid structures, as well as their strengths and weaknesses. We expect that this review will aid in understanding how these structures are characterised and how they contribute to related biological processes and diseases.
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Affiliation(s)
- Xiaohui Shi
- Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, The first Affiliated Hospital of WMU; Beijing Institutes of Life Science, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Ouhai District, Wenzhou 325000, China
| | - Huajing Teng
- Department of Radiation Oncology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education) at Peking University Cancer Hospital and Institute, Ouhai District, Wenzhou 325000, China
| | - Zhongsheng Sun
- Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, The first Affiliated Hospital of WMU; Beijing Institutes of Life Science, Chinese Academy of Sciences; CAS Center for Excellence in Biotic Interactions and State Key Laboratory of Integrated Management of Pest Insects and Rodents, University of Chinese Academy of Sciences; Institute of Genomic Medicine, Wenzhou Medical University; IBMC-BGI Center, the Cancer Hospital of the University of Chinese Academy of Sciences (Zhejiang Cancer Hospital); Institute of Basic Medicine and Cancer (IBMC), Chinese Academy of Sciences, Ouhai District, Wenzhou 325000, China
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7
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Abstract
Enhancers confer precise spatiotemporal patterns of gene expression in response to developmental and environmental stimuli. Over the last decade, the transcription of enhancer RNAs (eRNAs) – nascent RNAs transcribed from active enhancers – has emerged as a key factor regulating enhancer activity. eRNAs are relatively short-lived RNA species that are transcribed at very high rates but also quickly degraded. Nevertheless, eRNAs are deeply intertwined within enhancer regulatory networks and are implicated in a number of transcriptional control mechanisms. Enhancers show changes in function and sequence over evolutionary time, raising questions about the relationship between enhancer sequences and eRNA function. Moreover, the vast majority of single nucleotide polymorphisms associated with human complex diseases map to the non-coding genome, with causal disease variants enriched within enhancers. In this Primer, we survey the diverse roles played by eRNAs in enhancer-dependent gene expression, evaluating different models for eRNA function. We also explore questions surrounding the genetic conservation of enhancers and how this relates to eRNA function and dysfunction. Summary: This Primer evaluates the ideas that underpin developing models for eRNA function, exploring cases in which perturbed eRNA function contributes to disease.
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Affiliation(s)
- Laura J. Harrison
- Molecular and Cellular Biology, School of Biosciences, Sheffield Institute For Nucleic Acids, The University of Sheffield, Firth Court, Western Bank , Sheffield S10 2TN , UK
| | - Daniel Bose
- Molecular and Cellular Biology, School of Biosciences, Sheffield Institute For Nucleic Acids, The University of Sheffield, Firth Court, Western Bank , Sheffield S10 2TN , UK
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Feng Y, Luo Z, Huang R, Yang X, Cheng X, Zhang W. Epigenomic Features and Potential Functions of K+ and Na+ Favorable DNA G-Quadruplexes in Rice. Int J Mol Sci 2022; 23:ijms23158404. [PMID: 35955535 PMCID: PMC9368837 DOI: 10.3390/ijms23158404] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 07/22/2022] [Accepted: 07/23/2022] [Indexed: 11/16/2022] Open
Abstract
DNA G-quadruplexes (G4s) are non-canonical four-stranded DNA structures involved in various biological processes in eukaryotes. Molecularly crowded solutions and monovalent cations have been reported to stabilize in vitro and in vivo G4 formation. However, how K+ and Na+ affect G4 formation genome-wide is still unclear in plants. Here, we conducted BG4-DNA-IP-seq, DNA immunoprecipitation with anti-BG4 antibody coupled with sequencing, under K+ and Na+ + PEG conditions in vitro. We found that K+-specific IP-G4s had a longer peak size, more GC and PQS content, and distinct AT and GC skews compared to Na+-specific IP-G4s. Moreover, K+- and Na+-specific IP-G4s exhibited differential subgenomic enrichment and distinct putative functional motifs for the binding of certain trans-factors. More importantly, we found that K+-specific IP-G4s were more associated with active marks, such as active histone marks, and low DNA methylation levels, as compared to Na+-specific IP-G4s; thus, K+-specific IP-G4s in combination with active chromatin features facilitate the expression of overlapping genes. In addition, K+- and Na+-specific IP-G4 overlapping genes exhibited differential GO (gene ontology) terms, suggesting they may have distinct biological relevance in rice. Thus, our study, for the first time, explores the effects of K+ and Na+ on global G4 formation in vitro, thereby providing valuable resources for functional G4 studies in rice. It will provide certain G4 loci for the biotechnological engineering of rice in the future.
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Affiliation(s)
- Yilong Feng
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Collaborative Innovation Center for Modern Crop Production Co-Sponsored by Province and Ministry (CIC-MCP), Nanjing Agricultural University, No.1 Weigang, Nanjing 210095, China; (Y.F.); (Z.L.); (R.H.); (X.C.)
| | - Zhenyu Luo
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Collaborative Innovation Center for Modern Crop Production Co-Sponsored by Province and Ministry (CIC-MCP), Nanjing Agricultural University, No.1 Weigang, Nanjing 210095, China; (Y.F.); (Z.L.); (R.H.); (X.C.)
| | - Ranran Huang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Collaborative Innovation Center for Modern Crop Production Co-Sponsored by Province and Ministry (CIC-MCP), Nanjing Agricultural University, No.1 Weigang, Nanjing 210095, China; (Y.F.); (Z.L.); (R.H.); (X.C.)
| | - Xueming Yang
- Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China;
| | - Xuejiao Cheng
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Collaborative Innovation Center for Modern Crop Production Co-Sponsored by Province and Ministry (CIC-MCP), Nanjing Agricultural University, No.1 Weigang, Nanjing 210095, China; (Y.F.); (Z.L.); (R.H.); (X.C.)
| | - Wenli Zhang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, Collaborative Innovation Center for Modern Crop Production Co-Sponsored by Province and Ministry (CIC-MCP), Nanjing Agricultural University, No.1 Weigang, Nanjing 210095, China; (Y.F.); (Z.L.); (R.H.); (X.C.)
- Correspondence: ; Tel.: +86-25-84396610; Fax: +86-25-84396302
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9
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Miller HE, Montemayor D, Abdul J, Vines A, Levy SA, Hartono SR, Sharma K, Frost B, Chédin F, Bishop AJR. Quality-controlled R-loop meta-analysis reveals the characteristics of R-loop consensus regions. Nucleic Acids Res 2022; 50:7260-7286. [PMID: 35758606 PMCID: PMC9303298 DOI: 10.1093/nar/gkac537] [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: 05/15/2022] [Accepted: 06/16/2022] [Indexed: 12/13/2022] Open
Abstract
R-loops are three-stranded nucleic acid structures formed from the hybridization of RNA and DNA. While the pathological consequences of R-loops have been well-studied to date, the locations, classes, and dynamics of physiological R-loops remain poorly understood. R-loop mapping studies provide insight into R-loop dynamics, but their findings are challenging to generalize. This is due to the narrow biological scope of individual studies, the limitations of each mapping modality, and, in some cases, poor data quality. In this study, we reprocessed 810 R-loop mapping datasets from a wide array of biological conditions and mapping modalities. From this data resource, we developed an accurate R-loop data quality control method, and we reveal the extent of poor-quality data within previously published studies. We then identified a set of high-confidence R-loop mapping samples and used them to define consensus R-loop sites called 'R-loop regions' (RL regions). In the process, we identified a stark divergence between RL regions detected by S9.6 and dRNH-based mapping methods, particularly with respect to R-loop size, location, and colocalization with RNA binding factors. Taken together, this work provides a much-needed method to assess R-loop data quality and offers novel context regarding the differences between dRNH- and S9.6-based R-loop mapping approaches.
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Affiliation(s)
- Henry E Miller
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA.,Greehey Children's Cancer Research Institute, UT Health San Antonio, San Antonio, TX, USA.,Bioinformatics Research Network, Atlanta, GA, USA
| | - Daniel Montemayor
- Department of Medicine, UT Health San Antonio, San Antonio, TX, USA.,Center for Precision Medicine, UT Health San Antonio, San Antonio, TX, USA
| | - Jebriel Abdul
- Bioinformatics Research Network, Atlanta, GA, USA.,Department of Biology, University of Ottawa, Ottawa, Canada
| | - Anna Vines
- Bioinformatics Research Network, Atlanta, GA, USA.,Faculty of Arts, University of Bristol, Bristol, U.K
| | - Simon A Levy
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA.,Bioinformatics Research Network, Atlanta, GA, USA.,Sam & Ann Barshop Institute for Longevity & Aging Studies, UT Health San Antonio, San Antonio, TX, USA.,Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, UT Health San Antonio, San Antonio, TX, USA
| | - Stella R Hartono
- Department of Molecular and Cellular Biology, UC Davis, Davis, CA, USA
| | - Kumar Sharma
- Department of Medicine, UT Health San Antonio, San Antonio, TX, USA.,Center for Precision Medicine, UT Health San Antonio, San Antonio, TX, USA
| | - Bess Frost
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA.,Sam & Ann Barshop Institute for Longevity & Aging Studies, UT Health San Antonio, San Antonio, TX, USA.,Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, UT Health San Antonio, San Antonio, TX, USA
| | - Frédéric Chédin
- Department of Molecular and Cellular Biology, UC Davis, Davis, CA, USA
| | - Alexander J R Bishop
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX, USA.,Greehey Children's Cancer Research Institute, UT Health San Antonio, San Antonio, TX, USA.,May's Cancer Center, UT Health San Antonio, San Antonio, TX, USA
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10
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Zhai LY, Liu JF, Zhao JJ, Su AM, Xi XG, Hou XM. Targeting the RNA G-Quadruplex and Protein Interactome for Antiviral Therapy. J Med Chem 2022; 65:10161-10182. [PMID: 35862260 DOI: 10.1021/acs.jmedchem.2c00649] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In recent years, G-quadruplexes (G4s), types of noncanonical four-stranded nucleic acid structures, have been identified in many viruses that threaten human health, such as HIV and Epstein-Barr virus. In this context, G4 ligands were designed to target the G4 structures, among which some have shown promising antiviral effects. In this Perspective, we first summarize the diversified roles of RNA G4s in different viruses. Next, we introduce small-molecule ligands developed as G4 modulators and highlight their applications in antiviral studies. In addition to G4s, we comprehensively review the medical intervention of G4-interacting proteins from both the virus (N protein, viral-encoded helicases, severe acute respiratory syndrome-unique domain, and Epstein-Barr nuclear antigen 1) and the host (heterogeneous nuclear ribonucleoproteins, RNA helicases, zinc-finger cellular nucelic acid-binding protein, and nucleolin) by inhibitors as an alternative way to disturb the normal functions of G4s. Finally, we discuss the challenges and opportunities in G4-based antiviral therapy.
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Affiliation(s)
- Li-Yan Zhai
- College of Life Sciences, Northwest A&F University, Xianyang, Shaanxi 712100, China
| | - Jing-Fan Liu
- College of Life Sciences, Northwest A&F University, Xianyang, Shaanxi 712100, China
| | - Jian-Jin Zhao
- College of Life Sciences, Northwest A&F University, Xianyang, Shaanxi 712100, China
| | - Ai-Min Su
- College of Life Sciences, Northwest A&F University, Xianyang, Shaanxi 712100, China
| | - Xu-Guang Xi
- College of Life Sciences, Northwest A&F University, Xianyang, Shaanxi 712100, China.,Laboratory of Biology and Applied Pharmacology, CNRS UMR 8113, IDA FR3242, ENS Paris-Saclay, Université Paris-Saclay, Gif-sur-Yvette 91190, France
| | - Xi-Miao Hou
- College of Life Sciences, Northwest A&F University, Xianyang, Shaanxi 712100, China
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11
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Pan X, Huang LF. Multi-omics to characterize the functional relationships of R-loops with epigenetic modifications, RNAPII transcription and gene expression. Brief Bioinform 2022; 23:6618633. [DOI: 10.1093/bib/bbac238] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 05/19/2022] [Accepted: 05/21/2022] [Indexed: 12/12/2022] Open
Abstract
Abstract
Abnormal accumulation of R-loops results in replication stress, genome instability, chromatin alterations and gene silencing. Little research has been done to characterize functional relationships among R-loops, histone marks, RNA polymerase II (RNAPII) transcription and gene regulation. We built extremely randomized trees (ETs) models to predict the genome-wide R-loops using RNAPII and multiple histone modifications chromatin immunoprecipitation (ChIP)-seq, DNase-seq, Global Run-On sequencing (GRO-seq) and R-loop profiling data. We compared the performance of ET models to multiple machine learning approaches, and the proposed ET models achieved the best and extremely robust performances. Epigenetic profiles are highly predictive of R-loops genome-widely and they are strongly associated with R-loop formation. In addition, the presence of R-loops is significantly correlated with RNAPII transcription activity, H3K4me3 and open chromatin around the transcription start site, and H3K9me1 and H3K9me3 around the transcription termination site. RNAPII pausing defects were correlated with 5′R-loops accumulation, and transcriptional termination defects and read-throughs were correlated with 3′R-loops accumulation. Furthermore, we found driver genes with 5′R-loops and RNAPII pausing defects express significantly higher and genes with 3′R-loops and read-through transcription express significantly lower than genes without R-loops. These driver genes are enriched with chromosomal instability, Hippo–Merlin signaling Dysregulation, DNA damage response and TGF-β pathways, indicating R-loops accumulating at the 5′ end of genes play oncogenic roles, whereas at the 3′ end of genes play tumor-suppressive roles in tumorigenesis.
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Affiliation(s)
- Xingxin Pan
- Division of Experimental Hematology and Cancer Biology , Brain Tumor Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229 , USA
| | - L Frank Huang
- Division of Experimental Hematology and Cancer Biology , Brain Tumor Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229 , USA
- Department of Pediatrics, University of Cincinnati College of Medicine , Cincinnati, OH 45229 , USA
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12
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Miller HE, Ilieva M, Bishop AJR, Uchida S. Current Status of Epitranscriptomic Marks Affecting lncRNA Structures and Functions. Noncoding RNA 2022; 8:ncrna8020023. [PMID: 35447886 PMCID: PMC9025719 DOI: 10.3390/ncrna8020023] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 03/21/2022] [Accepted: 03/25/2022] [Indexed: 11/30/2022] Open
Abstract
Long non-coding RNAs (lncRNAs) belong to a class of non-protein-coding RNAs with their lengths longer than 200 nucleotides. Most of the mammalian genome is transcribed as RNA, yet only a small percent of the transcribed RNA corresponds to exons of protein-coding genes. Thus, the number of lncRNAs is predicted to be several times higher than that of protein-coding genes. Because of sheer number of lncRNAs, it is often difficult to elucidate the functions of all lncRNAs, especially those arising from their relationship to their binding partners, such as DNA, RNA, and proteins. Due to their binding to other macromolecules, it has become evident that the structures of lncRNAs influence their functions. In this regard, the recent development of epitranscriptomics (the field of study to investigate RNA modifications) has become important to further elucidate the structures and functions of lncRNAs. In this review, the current status of lncRNA structures and functions influenced by epitranscriptomic marks is discussed.
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Affiliation(s)
- Henry E. Miller
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX 78229, USA; (H.E.M.); (A.J.R.B.)
- Greehey Children’s Cancer Research Institute, UT Health San Antonio, San Antonio, TX 78229, USA
- Bioinformatics Research Network, Atlanta, GA 30317, USA
| | - Mirolyuba Ilieva
- Center for RNA Medicine, Department of Clinical Medicine, Aalborg University, DK-2450 Copenhagen SV, Denmark;
| | - Alexander J. R. Bishop
- Department of Cell Systems and Anatomy, UT Health San Antonio, San Antonio, TX 78229, USA; (H.E.M.); (A.J.R.B.)
- Greehey Children’s Cancer Research Institute, UT Health San Antonio, San Antonio, TX 78229, USA
- May’s Cancer Center, UT Health San Antonio, San Antonio, TX 78229, USA
| | - Shizuka Uchida
- Center for RNA Medicine, Department of Clinical Medicine, Aalborg University, DK-2450 Copenhagen SV, Denmark;
- Correspondence: or
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13
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Kim S, Hwang S. G-Quadruplex Matters in Tissue-Specific Tumorigenesis by BRCA1 Deficiency. Genes (Basel) 2022; 13:genes13030391. [PMID: 35327946 PMCID: PMC8948836 DOI: 10.3390/genes13030391] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/17/2022] [Accepted: 02/18/2022] [Indexed: 12/14/2022] Open
Abstract
How and why distinct genetic alterations, such as BRCA1 mutation, promote tumorigenesis in certain tissues, but not others, remain an important issue in cancer research. The underlying mechanisms may reveal tissue-specific therapeutic vulnerabilities. Although the roles of BRCA1, such as DNA damage repair and stalled fork stabilization, obviously contribute to tumor suppression, these ubiquitously important functions cannot explain tissue-specific tumorigenesis by BRCA1 mutations. Recent advances in our understanding of the cancer genome and fundamental cellular processes on DNA, such as transcription and DNA replication, have provided new insights regarding BRCA1-associated tumorigenesis, suggesting that G-quadruplex (G4) plays a critical role. In this review, we summarize the importance of G4 structures in mutagenesis of the cancer genome and cell type-specific gene regulation, and discuss a recently revealed molecular mechanism of G4/base excision repair (BER)-mediated transcriptional activation. The latter adequately explains the correlation between the accumulation of unresolved transcriptional regulatory G4s and multi-level genomic alterations observed in BRCA1-associated tumors. In summary, tissue-specific tumorigenesis by BRCA1 deficiency can be explained by cell type-specific levels of transcriptional regulatory G4s and the role of BRCA1 in resolving it. This mechanism would provide an integrated understanding of the initiation and development of BRCA1-associated tumors.
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Affiliation(s)
- Sanghyun Kim
- Department of Biomedical Science, College of Life Science, CHA University, Sungnam 13488, Korea;
| | - Sohyun Hwang
- Department of Biomedical Science, College of Life Science, CHA University, Sungnam 13488, Korea;
- Department of Pathology, CHA Bundang Medical Center, CHA University School of Medicine, Sungnam 13496, Korea
- Correspondence:
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14
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Camarillo R, Jimeno S, Huertas P. The Effect of Atypical Nucleic Acids Structures in DNA Double Strand Break Repair: A Tale of R-loops and G-Quadruplexes. Front Genet 2021; 12:742434. [PMID: 34691154 PMCID: PMC8531813 DOI: 10.3389/fgene.2021.742434] [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: 07/16/2021] [Accepted: 09/28/2021] [Indexed: 01/08/2023] Open
Abstract
The fine tuning of the DNA double strand break repair pathway choice relies on different regulatory layers that respond to environmental and local cues. Among them, the presence of non-canonical nucleic acids structures seems to create challenges for the repair of nearby DNA double strand breaks. In this review, we focus on the recently published effects of G-quadruplexes and R-loops on DNA end resection and homologous recombination. Finally, we hypothesized a connection between those two atypical DNA structures in inhibiting the DNA end resection step of HR.
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Affiliation(s)
- Rosa Camarillo
- Departamento de Genética, Universidad de Sevilla, Sevilla, Spain.,Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla, Spain
| | - Sonia Jimeno
- Departamento de Genética, Universidad de Sevilla, Sevilla, Spain.,Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla, Spain
| | - Pablo Huertas
- Departamento de Genética, Universidad de Sevilla, Sevilla, Spain.,Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla, Spain
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15
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Transcription/Replication Conflicts in Tumorigenesis and Their Potential Role as Novel Therapeutic Targets in Multiple Myeloma. Cancers (Basel) 2021; 13:cancers13153755. [PMID: 34359660 PMCID: PMC8345052 DOI: 10.3390/cancers13153755] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/13/2021] [Accepted: 07/22/2021] [Indexed: 12/24/2022] Open
Abstract
Simple Summary Multiple myeloma is a hematologic cancer characterized by the accumulation of malignant plasma cells in the bone marrow. It remains a mostly incurable disease due to the inability to overcome refractory disease and drug-resistant relapse. Oncogenic transformation of PC in multiple myeloma is thought to occur within the secondary lymphoid organs. However, the precise molecular events leading to myelomagenesis remain obscure. Here, we identified genes involved in the prevention and the resolution of conflicts between the replication and transcription significantly overexpressed during the plasma cell differentiation process and in multiple myeloma cells. We discussed the potential role of these factors in myelomagenesis and myeloma biology. The specific targeting of these factors might constitute a new therapeutic strategy in multiple myeloma. Abstract Plasma cells (PCs) have an essential role in humoral immune response by secretion of antibodies, and represent the final stage of B lymphocytes differentiation. During this differentiation, the pre-plasmablastic stage is characterized by highly proliferative cells that start to secrete immunoglobulins (Igs). Thus, replication and transcription must be tightly regulated in these cells to avoid transcription/replication conflicts (TRCs), which could increase replication stress and lead to genomic instability. In this review, we analyzed expression of genes involved in TRCs resolution during B to PC differentiation and identified 41 genes significantly overexpressed in the pre-plasmablastic stage. This illustrates the importance of mechanisms required for adequate processing of TRCs during PCs differentiation. Furthermore, we identified that several of these factors were also found overexpressed in purified PCs from patients with multiple myeloma (MM) compared to normal PCs. Malignant PCs produce high levels of Igs concomitantly with cell cycle deregulation. Therefore, increasing the TRCs occurring in MM cells could represent a potent therapeutic strategy for MM patients. Here, we describe the potential roles of TRCs resolution factors in myelomagenesis and discuss the therapeutic interest of targeting the TRCs resolution machinery in MM.
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16
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Ramachandran S, Ma TS, Griffin J, Ng N, Foskolou IP, Hwang MS, Victori P, Cheng WC, Buffa FM, Leszczynska KB, El-Khamisy SF, Gromak N, Hammond EM. Hypoxia-induced SETX links replication stress with the unfolded protein response. Nat Commun 2021; 12:3686. [PMID: 34140498 PMCID: PMC8211819 DOI: 10.1038/s41467-021-24066-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 05/31/2021] [Indexed: 02/07/2023] Open
Abstract
Tumour hypoxia is associated with poor patient prognosis and therapy resistance. A unique transcriptional response is initiated by hypoxia which includes the rapid activation of numerous transcription factors in a background of reduced global transcription. Here, we show that the biological response to hypoxia includes the accumulation of R-loops and the induction of the RNA/DNA helicase SETX. In the absence of hypoxia-induced SETX, R-loop levels increase, DNA damage accumulates, and DNA replication rates decrease. Therefore, suggesting that, SETX plays a role in protecting cells from DNA damage induced during transcription in hypoxia. Importantly, we propose that the mechanism of SETX induction in hypoxia is reliant on the PERK/ATF4 arm of the unfolded protein response. These data not only highlight the unique cellular response to hypoxia, which includes both a replication stress-dependent DNA damage response and an unfolded protein response but uncover a novel link between these two distinct pathways.
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Affiliation(s)
- Shaliny Ramachandran
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Tiffany S Ma
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Jon Griffin
- Department of Molecular Biology and Biotechnology, Healthy Lifespan and Neuroscience Institute, Firth Court, University of Sheffield, Sheffield, UK
- Department of Histopathology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
| | - Natalie Ng
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Iosifina P Foskolou
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Ming-Shih Hwang
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Pedro Victori
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Wei-Chen Cheng
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Francesca M Buffa
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Katarzyna B Leszczynska
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
- Laboratory of Molecular Neurobiology, Neurobiology Center, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Sherif F El-Khamisy
- Department of Molecular Biology and Biotechnology, Healthy Lifespan and Neuroscience Institute, Firth Court, University of Sheffield, Sheffield, UK
- Institute of Cancer Therapeutics, University of Bradford, Bradford, UK
| | - Natalia Gromak
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Ester M Hammond
- Department of Oncology, Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK.
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17
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Dettori LG, Torrejon D, Chakraborty A, Dutta A, Mohamed M, Papp C, Kuznetsov VA, Sung P, Feng W, Bah A. A Tale of Loops and Tails: The Role of Intrinsically Disordered Protein Regions in R-Loop Recognition and Phase Separation. Front Mol Biosci 2021; 8:691694. [PMID: 34179096 PMCID: PMC8222781 DOI: 10.3389/fmolb.2021.691694] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 05/14/2021] [Indexed: 11/13/2022] Open
Abstract
R-loops are non-canonical, three-stranded nucleic acid structures composed of a DNA:RNA hybrid, a displaced single-stranded (ss)DNA, and a trailing ssRNA overhang. R-loops perform critical biological functions under both normal and disease conditions. To elucidate their cellular functions, we need to understand the mechanisms underlying R-loop formation, recognition, signaling, and resolution. Previous high-throughput screens identified multiple proteins that bind R-loops, with many of these proteins containing folded nucleic acid processing and binding domains that prevent (e.g., topoisomerases), resolve (e.g., helicases, nucleases), or recognize (e.g., KH, RRMs) R-loops. However, a significant number of these R-loop interacting Enzyme and Reader proteins also contain long stretches of intrinsically disordered regions (IDRs). The precise molecular and structural mechanisms by which the folded domains and IDRs synergize to recognize and process R-loops or modulate R-loop-mediated signaling have not been fully explored. While studying one such modular R-loop Reader, the Fragile X Protein (FMRP), we unexpectedly discovered that the C-terminal IDR (C-IDR) of FMRP is the predominant R-loop binding site, with the three N-terminal KH domains recognizing the trailing ssRNA overhang. Interestingly, the C-IDR of FMRP has recently been shown to undergo spontaneous Liquid-Liquid Phase Separation (LLPS) assembly by itself or in complex with another non-canonical nucleic acid structure, RNA G-quadruplex. Furthermore, we have recently shown that FMRP can suppress persistent R-loops that form during transcription, a process that is also enhanced by LLPS via the assembly of membraneless transcription factories. These exciting findings prompted us to explore the role of IDRs in R-loop processing and signaling proteins through a comprehensive bioinformatics and computational biology study. Here, we evaluated IDR prevalence, sequence composition and LLPS propensity for the known R-loop interactome. We observed that, like FMRP, the majority of the R-loop interactome, especially Readers, contains long IDRs that are highly enriched in low complexity sequences with biased amino acid composition, suggesting that these IDRs could directly interact with R-loops, rather than being “mere flexible linkers” connecting the “functional folded enzyme or binding domains”. Furthermore, our analysis shows that several proteins in the R-loop interactome are either predicted to or have been experimentally demonstrated to undergo LLPS or are known to be associated with phase separated membraneless organelles. Thus, our overall results present a thought-provoking hypothesis that IDRs in the R-loop interactome can provide a functional link between R-loop recognition via direct binding and downstream signaling through the assembly of LLPS-mediated membrane-less R-loop foci. The absence or dysregulation of the function of IDR-enriched R-loop interactors can potentially lead to severe genomic defects, such as the widespread R-loop-mediated DNA double strand breaks that we recently observed in Fragile X patient-derived cells.
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Affiliation(s)
- Leonardo G Dettori
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Diego Torrejon
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Arijita Chakraborty
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Arijit Dutta
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Mohamed Mohamed
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Csaba Papp
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States.,Department of Urology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Vladimir A Kuznetsov
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY, United States.,Bioinformatics Institute, ASTAR Biomedical Institutes, Singapore, Singapore
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Alaji Bah
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
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18
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Sengupta P, Bose D, Chatterjee S. The Molecular Tête-à-Tête between G-Quadruplexes and the i-motif in the Human Genome. Chembiochem 2021; 22:1517-1537. [PMID: 33355980 DOI: 10.1002/cbic.202000703] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 12/16/2020] [Indexed: 12/22/2022]
Abstract
G-Quadruplex (GQ) and i-motif structures are the paradigmatic examples of nonclassical tetrastranded nucleic acids having multifarious biological functions and widespread applications in therapeutics and material science. Recently, tetraplexes emerged as promising anticancer targets due to their structural robustness, gene-regulatory roles, and predominant distribution at specific loci of oncogenes. However, it is arguable whether the i-motif evolves in the complementary single-stranded region after GQ formation in its opposite strand and vice versa. In this review, we address the prerequisites and significance of the simultaneous and/or mutually exclusive formation of GQ and i-motif structures at complementary and sequential positions in duplexes in the cellular milieu. We discussed how their dynamic interplay Sets up cellular homeostasis and exacerbates carcinogenesis. The review gives insights into the spatiotemporal formation of GQ and i-motifs that could be harnessed to design different types of reporter systems and diagnostic platforms for potential bioanalytical and therapeutic intervention.
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Affiliation(s)
- Pallabi Sengupta
- Department of Biophysics, Bose Institute, Centenary Campus, P-1/12, C.I.T. Scheme VIIM, Kankurgachi, Kolkata, 700054, West Bengal, India
| | - Debopriya Bose
- Department of Biophysics, Bose Institute, Centenary Campus, P-1/12, C.I.T. Scheme VIIM, Kankurgachi, Kolkata, 700054, West Bengal, India
| | - Subhrangsu Chatterjee
- Department of Biophysics, Bose Institute, Centenary Campus, P-1/12, C.I.T. Scheme VIIM, Kankurgachi, Kolkata, 700054, West Bengal, India
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19
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Kharel P, Becker G, Tsvetkov V, Ivanov P. Properties and biological impact of RNA G-quadruplexes: from order to turmoil and back. Nucleic Acids Res 2020; 48:12534-12555. [PMID: 33264409 PMCID: PMC7736831 DOI: 10.1093/nar/gkaa1126] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/23/2020] [Accepted: 11/06/2020] [Indexed: 12/12/2022] Open
Abstract
Guanine-quadruplexes (G4s) are non-canonical four-stranded structures that can be formed in guanine (G) rich nucleic acid sequences. A great number of G-rich sequences capable of forming G4 structures have been described based on in vitro analysis, and evidence supporting their formation in live cells continues to accumulate. While formation of DNA G4s (dG4s) within chromatin in vivo has been supported by different chemical, imaging and genomic approaches, formation of RNA G4s (rG4s) in vivo remains a matter of discussion. Recent data support the dynamic nature of G4 formation in the transcriptome. Such dynamic fluctuation of rG4 folding-unfolding underpins the biological significance of these structures in the regulation of RNA metabolism. Moreover, rG4-mediated functions may ultimately be connected to mechanisms underlying disease pathologies and, potentially, provide novel options for therapeutics. In this framework, we will review the landscape of rG4s within the transcriptome, focus on their potential impact on biological processes, and consider an emerging connection of these functions in human health and disease.
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Affiliation(s)
- Prakash Kharel
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Gertraud Becker
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Vladimir Tsvetkov
- Computational Oncology Group, I. M. Sechenov First Moscow State Medical University, Moscow 119146, Russia
- Federal Research and Clinical Center for Physical-Chemical Medicine, Federal Medical Biological Agency, Moscow 119435, Russia
- A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow 117912, Russia
| | - Pavel Ivanov
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
- Harvard Initiative for RNA Medicine, Boston, MA 02115, USA
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20
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Zhang J, Fakharzadeh A, Pan F, Roland C, Sagui C. Atypical structures of GAA/TTC trinucleotide repeats underlying Friedreich's ataxia: DNA triplexes and RNA/DNA hybrids. Nucleic Acids Res 2020; 48:9899-9917. [PMID: 32821947 PMCID: PMC7515735 DOI: 10.1093/nar/gkaa665] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/27/2020] [Accepted: 08/04/2020] [Indexed: 11/13/2022] Open
Abstract
Expansion of the GAA/TTC repeats in the first intron of the FXN gene causes Friedreich's ataxia. Non-canonical structures are linked to this expansion. DNA triplexes and R-loops are believed to arrest transcription, which results in frataxin deficiency and eventual neurodegeneration. We present a systematic in silico characterization of the possible DNA triplexes that could be assembled with GAA and TTC strands; the two hybrid duplexes [r(GAA):d(TTC) and d(GAA):r(UUC)] in an R-loop; and three hybrid triplexes that could form during bidirectional transcription when the non-template DNA strand bonds with the hybrid duplex (collapsed R-loops, where the two DNA strands remain antiparallel). For both Y·R:Y and R·R:Y DNA triplexes, the parallel third strand orientation is more stable; both parallel and antiparallel protonated d(GA+A)·d(GAA):d(TTC) triplexes are stable. Apparent contradictions in the literature about the R·R:Y triplex stability is probably due to lack of molecular resolution, since shifting the third strand by a single nucleotide alters the stability ranking. In the collapsed R-loops, antiparallel d(TTC+)·d(GAA):r(UUC) is unstable, while parallel d(GAA)·r(GAA):d(TTC) and d(GA+A)·r(GAA):d(TTC) are stable. In addition to providing new structural perspectives for specific therapeutic aims, our results contribute to a systematic structural basis for the emerging field of quantitative R-loop biology.
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Affiliation(s)
- Jiahui Zhang
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Ashkan Fakharzadeh
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Feng Pan
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA.,Department of Statistics, Florida State University, Tallahassee, FL 32306, USA
| | - Christopher Roland
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Celeste Sagui
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
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21
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Wu W, Bhowmick R, Vogel I, Özer Ö, Ghisays F, Thakur RS, Sanchez de Leon E, Richter PH, Ren L, Petrini JH, Hickson ID, Liu Y. RTEL1 suppresses G-quadruplex-associated R-loops at difficult-to-replicate loci in the human genome. Nat Struct Mol Biol 2020; 27:424-437. [PMID: 32398827 DOI: 10.1038/s41594-020-0408-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 02/26/2020] [Indexed: 12/14/2022]
Abstract
Oncogene activation during tumorigenesis generates DNA replication stress, a known driver of genome rearrangements. In response to replication stress, certain loci, such as common fragile sites and telomeres, remain under-replicated during interphase and subsequently complete locus duplication in mitosis in a process known as 'MiDAS'. Here, we demonstrate that RTEL1 (regulator of telomere elongation helicase 1) has a genome-wide role in MiDAS at loci prone to form G-quadruplex-associated R-loops, in a process that is dependent on its helicase function. We reveal that SLX4 is required for the timely recruitment of RTEL1 to the affected loci, which in turn facilitates recruitment of other proteins required for MiDAS, including RAD52 and POLD3. Our findings demonstrate that RTEL1 is required for MiDAS and suggest that RTEL1 maintains genome stability by resolving conflicts that can arise between the replication and transcription machineries.
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Affiliation(s)
- Wei Wu
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
| | - Rahul Bhowmick
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
| | - Ivan Vogel
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
| | - Özgün Özer
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
- Institute of Cancer Research, London, UK
| | - Fiorella Ghisays
- Laboratory of Chromosome Biology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Roshan S Thakur
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
| | - Esther Sanchez de Leon
- Laboratory of Chromosome Biology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Philipp H Richter
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
| | - Liqun Ren
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark
- The Basic Medical Research Institute, Chengde Medical University, Chengde, China
| | - John H Petrini
- Laboratory of Chromosome Biology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - Ian D Hickson
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark.
| | - Ying Liu
- Center for Chromosome Stability, University of Copenhagen, Copenhagen, Denmark.
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Veetil RT, Malhotra N, Dubey A, Seshasayee ASN. Laboratory Evolution Experiments Help Identify a Predominant Region of Constitutive Stable DNA Replication Initiation. mSphere 2020; 5:e00939-19. [PMID: 32102945 PMCID: PMC7045392 DOI: 10.1128/msphere.00939-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/06/2020] [Indexed: 01/06/2023] Open
Abstract
The bacterium Escherichia coli can initiate replication in the absence of the replication initiator protein DnaA and/or the canonical origin of replication oriC in a ΔrnhA background. This phenomenon, which can be primed by R-loops, is called constitutive stable DNA replication (cSDR). Whether DNA replication during cSDR initiates in a stochastic manner through the length of the chromosome or at specific sites and how E. coli can find adaptations to loss of fitness caused by cSDR remain inadequately answered. We use laboratory evolution experiments of ΔrnhA-ΔdnaA strains followed by deep sequencing to show that DNA replication preferentially initiates within a broad region located ∼0.4 to 0.7 Mb clockwise of oriC. This region includes many bisulfite-sensitive sites, which have been previously defined as R-loop-forming regions, and includes a site containing sequence motifs that favor R-loop formation. Initiation from this region would result in head-on replication-transcription conflicts at rRNA loci. Inversions of these rRNA loci, which can partly resolve these conflicts, help the bacterium suppress the fitness defects of cSDR. These inversions partially restore the gene expression changes brought about by cSDR. The inversion, however, increases the possibility of conflicts at essential mRNA genes, which would utilize only a minuscule fraction of RNA polymerase molecules, most of which transcribe rRNA genes. Whether subsequent adaptive strategies would attempt to resolve these conflicts remains an open question.IMPORTANCE The bacterium E. coli can replicate its DNA even in the absence of the molecules that are required for canonical replication initiation. This often requires the formation of RNA-DNA hybrid structures and is referred to as constitutive stable DNA replication (cSDR). Where on the chromosome does cSDR initiate? We answer this question using laboratory evolution experiments and genomics and show that selection favors cSDR initiation predominantly at a region ∼0.6 Mb clockwise of oriC. Initiation from this site will result in more head-on collisions of DNA polymerase with RNA polymerase operating on rRNA loci. The bacterium adapts to this problem by inverting a region of the genome including several rRNA loci such that head-on collisions between the two polymerases are minimized. Understanding such evolutionary strategies in the context of cSDR can provide insights into the potential causes of resistance to antibiotics that target initiation of DNA replication.
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Affiliation(s)
- Reshma T Veetil
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Gandhi Krishi Vigyan Kendra, Bengaluru, Karnataka, India
- School of Life Science, The University of Trans-Disciplinary Health Sciences & Technology (TDU), Bengaluru, Karnataka, India
| | - Nitish Malhotra
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Gandhi Krishi Vigyan Kendra, Bengaluru, Karnataka, India
| | - Akshara Dubey
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Gandhi Krishi Vigyan Kendra, Bengaluru, Karnataka, India
| | - Aswin Sai Narain Seshasayee
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Gandhi Krishi Vigyan Kendra, Bengaluru, Karnataka, India
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From R-Loops to G-Quadruplexes: Emerging New Threats for the Replication Fork. Int J Mol Sci 2020; 21:ijms21041506. [PMID: 32098397 PMCID: PMC7073102 DOI: 10.3390/ijms21041506] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 02/14/2020] [Accepted: 02/20/2020] [Indexed: 12/12/2022] Open
Abstract
Replicating the entire genome is one of the most complex tasks for all organisms. Research carried out in the last few years has provided us with a clearer picture on how cells preserve genomic information from the numerous insults that may endanger its stability. Different DNA repair pathways, coping with exogenous or endogenous threat, have been dissected at the molecular level. More recently, there has been an increasing interest towards intrinsic obstacles to genome replication, paving the way to a novel view on genomic stability. Indeed, in some cases, the movement of the replication fork can be hindered by the presence of stable DNA: RNA hybrids (R-loops), the folding of G-rich sequences into G-quadruplex structures (G4s) or repetitive elements present at Common Fragile Sites (CFS). Although differing in their nature and in the way they affect the replication fork, all of these obstacles are a source of replication stress. Replication stress is one of the main hallmarks of cancer and its prevention is becoming increasingly important as a target for future chemotherapeutics. Here we will try to summarize how these three obstacles are generated and how the cells handle replication stress upon their encounter. Finally, we will consider their role in cancer and their exploitation in current chemotherapeutic approaches.
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Regulatory R-loops as facilitators of gene expression and genome stability. Nat Rev Mol Cell Biol 2020; 21:167-178. [PMID: 32005969 DOI: 10.1038/s41580-019-0206-3] [Citation(s) in RCA: 278] [Impact Index Per Article: 69.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/17/2019] [Indexed: 12/23/2022]
Abstract
R-loops are three-stranded structures that harbour an RNA-DNA hybrid and frequently form during transcription. R-loop misregulation is associated with DNA damage, transcription elongation defects, hyper-recombination and genome instability. In contrast to such 'unscheduled' R-loops, evidence is mounting that cells harness the presence of RNA-DNA hybrids in scheduled, 'regulatory' R-loops to promote DNA transactions, including transcription termination and other steps of gene regulation, telomere stability and DNA repair. R-loops formed by cellular RNAs can regulate histone post-translational modification and may be recognized by dedicated reader proteins. The two-faced nature of R-loops implies that their formation, location and timely removal must be tightly regulated. In this Perspective, we discuss the cellular processes that regulatory R-loops modulate, the regulation of R-loops and the potential differences that may exist between regulatory R-loops and unscheduled R-loops.
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25
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Fleming AM, Burrows CJ. Interplay of Guanine Oxidation and G-Quadruplex Folding in Gene Promoters. J Am Chem Soc 2020; 142:1115-1136. [PMID: 31880930 PMCID: PMC6988379 DOI: 10.1021/jacs.9b11050] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Living in an oxygen atmosphere demands an ability to thrive in the presence of reactive oxygen species (ROS). Aerobic organisms have successfully found solutions to the oxidative threats imposed by ROS by evolving an elaborate detoxification system, upregulating ROS during inflammation, and utilizing ROS as messenger molecules. In this Perspective, recent studies are discussed that demonstrate ROS as signaling molecules for gene regulation by combining two emergent properties of the guanine (G) heterocycle in DNA, namely, oxidation sensitivity and a propensity for G-quadruplex (G4) folding, both of which depend upon sequence context. In human gene promoters, this results from an elevated 5'-GG-3' dinucleotide frequency and GC enrichment near transcription start sites. Oxidation of DNA by ROS drives conversion of G to 8-oxo-7,8-dihydroguanine (OG) to mark target promoters for base excision repair initiated by OG-glycosylase I (OGG1). Sequence-dependent mechanisms for gene activation are available to OGG1 to induce transcription. Either OGG1 releases OG to yield an abasic site driving formation of a non-canonical fold, such as a G4, to be displayed to apurinic/apyrimidinic 1 (APE1) and stalling on the fold to recruit activating factors, or OGG1 binds OG and facilitates activator protein recruitment. The mechanisms described drive induction of stress response, DNA repair, or estrogen-induced genes, and these pathways are novel potential anticancer targets for therapeutic intervention. Chemical concepts provide a framework to discuss the regulatory or possible epigenetic potential of the OG modification in DNA, in which DNA "damage" and non-canonical folds collaborate to turn on or off gene expression. The next steps for scientific discovery in this growing field are discussed.
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Affiliation(s)
- Aaron M. Fleming
- 315 South 1400 East, Dept. of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA
| | - Cynthia J. Burrows
- 315 South 1400 East, Dept. of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA
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26
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Carrasco-Salas Y, Malapert A, Sulthana S, Molcrette B, Chazot-Franguiadakis L, Bernard P, Chédin F, Faivre-Moskalenko C, Vanoosthuyse V. The extruded non-template strand determines the architecture of R-loops. Nucleic Acids Res 2020; 47:6783-6795. [PMID: 31066439 PMCID: PMC6648340 DOI: 10.1093/nar/gkz341] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 04/16/2019] [Accepted: 04/26/2019] [Indexed: 01/05/2023] Open
Abstract
Three-stranded R-loop structures have been associated with genomic instability phenotypes. What underlies their wide-ranging effects on genome stability remains poorly understood. Here we combined biochemical and atomic force microscopy approaches with single molecule R-loop footprinting to demonstrate that R-loops formed at the model Airn locus in vitro adopt a defined set of three-dimensional conformations characterized by distinct shapes and volumes, which we call R-loop objects. Interestingly, we show that these R-loop objects impose specific physical constraints on the DNA, as revealed by the presence of stereotypical angles in the surrounding DNA. Biochemical probing and mutagenesis experiments revealed that the formation of R-loop objects at Airn is dictated by the extruded non-template strand, suggesting that R-loops possess intrinsic sequence-driven properties. Consistent with this, we show that R-loops formed at the fission yeast gene sum3 do not form detectable R-loop objects. Our results reveal that R-loops differ by their architectures and that the organization of the non-template strand is a fundamental characteristic of R-loops, which could explain that only a subset of R-loops is associated with replication-dependent DNA breaks.
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Affiliation(s)
- Yeraldinne Carrasco-Salas
- Université de Lyon, ENSL, UCBL, CNRS, Laboratoire de Physique, 46 Allée d'Italie, 69007 Lyon, France
| | - Amélie Malapert
- Université de Lyon, ENSL, UCBL, CNRS, Laboratory of Biology and Modelling of the Cell (LBMC), 46 Allée d'Italie, 69007 Lyon, France
| | - Shaheen Sulthana
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Bastien Molcrette
- Université de Lyon, ENSL, UCBL, CNRS, Laboratoire de Physique, 46 Allée d'Italie, 69007 Lyon, France
| | - Léa Chazot-Franguiadakis
- Université de Lyon, ENSL, UCBL, CNRS, Laboratoire de Physique, 46 Allée d'Italie, 69007 Lyon, France
| | - Pascal Bernard
- Université de Lyon, ENSL, UCBL, CNRS, Laboratory of Biology and Modelling of the Cell (LBMC), 46 Allée d'Italie, 69007 Lyon, France
| | - Frédéric Chédin
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | | | - Vincent Vanoosthuyse
- Université de Lyon, ENSL, UCBL, CNRS, Laboratory of Biology and Modelling of the Cell (LBMC), 46 Allée d'Italie, 69007 Lyon, France
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27
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Holt IJ. The mitochondrial R-loop. Nucleic Acids Res 2019; 47:5480-5489. [PMID: 31045202 PMCID: PMC6582354 DOI: 10.1093/nar/gkz277] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 03/11/2019] [Accepted: 04/29/2019] [Indexed: 12/18/2022] Open
Abstract
The DNA in mitochondria contributes essential components of the organelle’s energy producing machinery that is essential for life. In 1971, many mitochondrial DNA molecules were found to have a third strand of DNA that maps to a region containing critical regulatory elements for transcription and replication. Forty-five years later, a third strand of RNA in the same region has been reported. This mitochondrial R-loop is present on thousands of copies of mitochondrial DNA per cell making it potentially the most abundant R-loop in nature. Here, I assess the discovery of the mitochondrial R-loop, discuss why it remained unrecognized for almost half a century and propose for it central roles in the replication, organization and expression of mitochondrial DNA, which if compromised can lead to disease states.
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Affiliation(s)
- Ian J Holt
- Biodonostia Health Research Institute, 20014 San Sebastián, Spain & IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain.,Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Royal Free Campus, London, NW3 2PF, UK.,CIBERNED (Center for Networked Biomedical Research on Neurodegenerative Diseases, Ministry of Economy and Competitiveness, Institute Carlos III), Madrid, Spain
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28
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Abstract
The repair of DNA double-strand breaks occurs through a series of defined steps that are evolutionarily conserved and well-understood in most experimental organisms. However, it is becoming increasingly clear that repair does not occur in isolation from other DNA transactions. Transcription of DNA produces topological changes, RNA species, and RNA-dependent protein complexes that can dramatically influence the efficiency and outcomes of DNA double-strand break repair. The transcription-associated history of several double-strand break repair factors is reviewed here, with an emphasis on their roles in regulating R-loops and the emerging role of R-loops in coordination of repair events. Evidence for nucleolytic processing of R-loops is also discussed, as well as the molecular tools commonly used to measure RNA-DNA hybrids in cells.
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Affiliation(s)
- Tanya T Paull
- The Department of Molecular Biosciences and the Howard Hughes Medical Institute, The University of Texas at Austin, Austin, TX, USA
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