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He Q, Wang F, Yao NY, O'Donnell ME, Li H. Structures of the human leading strand Polε-PCNA holoenzyme. Nat Commun 2024; 15:7847. [PMID: 39245668 PMCID: PMC11381554 DOI: 10.1038/s41467-024-52257-x] [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: 05/18/2024] [Accepted: 09/02/2024] [Indexed: 09/10/2024] Open
Abstract
In eukaryotes, the leading strand DNA is synthesized by Polε and the lagging strand by Polδ. These replicative polymerases have higher processivity when paired with the DNA clamp PCNA. While the structure of the yeast Polε catalytic domain has been determined, how Polε interacts with PCNA is unknown in any eukaryote, human or yeast. Here we report two cryo-EM structures of human Polε-PCNA-DNA complex, one in an incoming nucleotide bound state and the other in a nucleotide exchange state. The structures reveal an unexpected three-point interface between the Polε catalytic domain and PCNA, with the conserved PIP (PCNA interacting peptide)-motif, the unique P-domain, and the thumb domain each interacting with a different protomer of the PCNA trimer. We propose that the multi-point interface prevents other PIP-containing factors from recruiting to PCNA while PCNA functions with Polε. Comparison of the two states reveals that the finger domain pivots around the [4Fe-4S] cluster-containing tip of the P-domain to regulate nucleotide exchange and incoming nucleotide binding.
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Affiliation(s)
- Qing He
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Feng Wang
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Nina Y Yao
- DNA Replication Laboratory and Howard Hughes Medical Institute, The Rockefeller University, New York, NY, USA
| | - Michael E O'Donnell
- DNA Replication Laboratory and Howard Hughes Medical Institute, The Rockefeller University, New York, NY, USA.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA.
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Zhou J, Zheng H, Zhang H, Yu W, Li B, Ye L, Wang L. MCM5 is a Novel Therapeutic Target for Glioblastoma. Onco Targets Ther 2024; 17:371-381. [PMID: 38765057 PMCID: PMC11100520 DOI: 10.2147/ott.s457600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Accepted: 05/08/2024] [Indexed: 05/21/2024] Open
Abstract
Objective MCM5 is a DNA licensing factor involved in cell proliferation and has been previously established as an excellent biomarker in a number of malignancies. Nevertheless, the role of MCM5 in GBM has not been fully clarified. The present study aimed to investigate the potential roles of MCM5 in the treatment of GBM and to elucidate its underlying mechanism, which is beneficial for developing new therapeutic strategies and predicting prognosis. Methods Firstly, we obtained transcriptomic and proteomic data from the TCGA and CPTAC databases on glioma patients. Employing the DeSeq2 R package, we then identified genes with joint differential expression in GBM tissues subjected to chemotherapy. To develop a prognostic risk score model, we performed univariate and multivariate Cox regression analyses. In vitro knockdown and overexpression of MCM5 were used to further investigate the biological functions of GBM cells. Additionally, we also delved into the upstream regulation of MCM5, revealing associations with several transcription factors. Finally, we investigated differences in immune cell infiltration and drug sensitivity across diverse risk groups identified in the prognostic risk model. Results In this study, the chemotherapy-treated GBM samples exhibited consistent alterations in 46 upregulated and 94 downregulated genes at both the mRNA and protein levels. Notably, MCM5 emerged as a gene with prognostic significance as well as potential therapeutic relevance. In vitro experiments subsequently validated the role of increased MCM5 expression in promoting GBM cell proliferation and resistance to TMZ. Correlations with transcription factors such as CREB1, CTCF, NFYB, NRF1, PBX1, TEAD1, and USF1 were discovered during upstream regulatory analysis, enriching our understanding of MCM5 regulatory mechanisms. The study additionally delves into immune cell infiltration and drug sensitivity, providing valuable insights for personalized treatment approaches. Conclusion This study identifies MCM5 as a key player in GBM, demonstrating its prognostic significance and potential therapeutic relevance by elucidating its role in promoting cell proliferation and resistance to chemotherapy.
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Affiliation(s)
- Jian Zhou
- Hyperbaric Oxygen Department, International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen, 518055, People’s Republic of China
- Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, School of Biomedical Engineering, Shenzhen University Medical School, Shenzhen, 518060, People’s Republic of China
| | - Housheng Zheng
- Hyperbaric Oxygen Department, International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen, 518055, People’s Republic of China
| | - Huiru Zhang
- Hyperbaric Oxygen Department, International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen, 518055, People’s Republic of China
| | - Wenqiang Yu
- Hyperbaric Oxygen Department, International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen, 518055, People’s Republic of China
| | - Baoer Li
- Hyperbaric Oxygen Department, International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen, 518055, People’s Republic of China
| | - Liang Ye
- Hyperbaric Oxygen Department, International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen, 518055, People’s Republic of China
| | - Lu Wang
- Hyperbaric Oxygen Department, International Cancer Center, Shenzhen University General Hospital, Shenzhen University Medical School, Shenzhen, 518055, People’s Republic of China
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Yin Z, Kilkenny ML, Ker DS, Pellegrini L. CryoEM insights into RNA primer synthesis by the human primosome. FEBS J 2024; 291:1813-1829. [PMID: 38335062 DOI: 10.1111/febs.17082] [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: 09/21/2023] [Revised: 11/24/2023] [Accepted: 01/26/2024] [Indexed: 02/12/2024]
Abstract
Eukaryotic DNA replication depends on the primosome - a complex of DNA polymerase alpha (Pol α) and primase - to initiate DNA synthesis by polymerisation of an RNA-DNA primer. Primer synthesis requires the tight coordination of primase and polymerase activities. Recent cryo-electron microscopy (cryoEM) analyses have elucidated the extensive conformational transitions required for RNA primer handover between primase and Pol α and primer elongation by Pol α. Because of the intrinsic flexibility of the primosome, however, structural information about the initiation of RNA primer synthesis is still lacking. Here, we capture cryoEM snapshots of the priming reaction to reveal the conformational trajectory of the human primosome that brings DNA primase subunits 1 and 2 (PRIM1 and PRIM2, respectively) together, poised for RNA synthesis. Furthermore, we provide experimental evidence for the continuous association of primase subunit PRIM2 with the RNA primer during primer synthesis, and for how both initiation and termination of RNA primer polymerisation are licenced by specific rearrangements of DNA polymerase alpha catalytic subunit (POLA1), the polymerase subunit of Pol α. Our findings fill a critical gap in our understanding of the conformational changes that underpin the synthesis of the RNA primer by the primosome. Together with existing evidence, they provide a complete description of the structural dynamics of the human primosome during DNA replication initiation.
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Affiliation(s)
- Zhan Yin
- Department of Biochemistry, University of Cambridge, UK
| | | | - De-Sheng Ker
- Department of Biochemistry, University of Cambridge, UK
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Piguet B, Houseley J. Transcription as source of genetic heterogeneity in budding yeast. Yeast 2024; 41:171-185. [PMID: 38196235 DOI: 10.1002/yea.3926] [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: 10/07/2023] [Revised: 12/10/2023] [Accepted: 12/20/2023] [Indexed: 01/11/2024] Open
Abstract
Transcription presents challenges to genome stability both directly, by altering genome topology and exposing single-stranded DNA to chemical insults and nucleases, and indirectly by introducing obstacles to the DNA replication machinery. Such obstacles include the RNA polymerase holoenzyme itself, DNA-bound regulatory factors, G-quadruplexes and RNA-DNA hybrid structures known as R-loops. Here, we review the detrimental impacts of transcription on genome stability in budding yeast, as well as the mitigating effects of transcription-coupled nucleotide excision repair and of systems that maintain DNA replication fork processivity and integrity. Interactions between DNA replication and transcription have particular potential to induce mutation and structural variation, but we conclude that such interactions must have only minor effects on DNA replication by the replisome with little if any direct mutagenic outcome. However, transcription can significantly impair the fidelity of replication fork rescue mechanisms, particularly Break Induced Replication, which is used to restart collapsed replication forks when other means fail. This leads to de novo mutations, structural variation and extrachromosomal circular DNA formation that contribute to genetic heterogeneity, but only under particular conditions and in particular genetic contexts, ensuring that the bulk of the genome remains extremely stable despite the seemingly frequent interactions between transcription and DNA replication.
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Nasheuer HP, Meaney AM. Starting DNA Synthesis: Initiation Processes during the Replication of Chromosomal DNA in Humans. Genes (Basel) 2024; 15:360. [PMID: 38540419 PMCID: PMC10969946 DOI: 10.3390/genes15030360] [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: 02/22/2024] [Revised: 03/09/2024] [Accepted: 03/11/2024] [Indexed: 06/14/2024] Open
Abstract
The initiation reactions of DNA synthesis are central processes during human chromosomal DNA replication. They are separated into two main processes: the initiation events at replication origins, the start of the leading strand synthesis for each replicon, and the numerous initiation events taking place during lagging strand DNA synthesis. In addition, a third mechanism is the re-initiation of DNA synthesis after replication fork stalling, which takes place when DNA lesions hinder the progression of DNA synthesis. The initiation of leading strand synthesis at replication origins is regulated at multiple levels, from the origin recognition to the assembly and activation of replicative helicase, the Cdc45-MCM2-7-GINS (CMG) complex. In addition, the multiple interactions of the CMG complex with the eukaryotic replicative DNA polymerases, DNA polymerase α-primase, DNA polymerase δ and ε, at replication forks play pivotal roles in the mechanism of the initiation reactions of leading and lagging strand DNA synthesis. These interactions are also important for the initiation of signalling at unperturbed and stalled replication forks, "replication stress" events, via ATR (ATM-Rad 3-related protein kinase). These processes are essential for the accurate transfer of the cells' genetic information to their daughters. Thus, failures and dysfunctions in these processes give rise to genome instability causing genetic diseases, including cancer. In their influential review "Hallmarks of Cancer: New Dimensions", Hanahan and Weinberg (2022) therefore call genome instability a fundamental function in the development process of cancer cells. In recent years, the understanding of the initiation processes and mechanisms of human DNA replication has made substantial progress at all levels, which will be discussed in the review.
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Affiliation(s)
- Heinz Peter Nasheuer
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, Biochemistry, University of Galway, H91 TK33 Galway, Ireland;
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Bellani MA, Shaik A, Majumdar I, Ling C, Seidman MM. The Response of the Replication Apparatus to Leading Template Strand Blocks. Cells 2023; 12:2607. [PMID: 37998342 PMCID: PMC10670059 DOI: 10.3390/cells12222607] [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: 10/23/2023] [Revised: 11/07/2023] [Accepted: 11/08/2023] [Indexed: 11/25/2023] Open
Abstract
Duplication of the genome requires the replication apparatus to overcome a variety of impediments, including covalent DNA adducts, the most challenging of which is on the leading template strand. Replisomes consist of two functional units, a helicase to unwind DNA and polymerases to synthesize it. The helicase is a multi-protein complex that encircles the leading template strand and makes the first contact with a leading strand adduct. The size of the channel in the helicase would appear to preclude transit by large adducts such as DNA: protein complexes (DPC). Here we discuss some of the extensively studied pathways that support replication restart after replisome encounters with leading template strand adducts. We also call attention to recent work that highlights the tolerance of the helicase for adducts ostensibly too large to pass through the central channel.
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Affiliation(s)
| | | | | | | | - Michael M. Seidman
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA; (M.A.B.)
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Xu Z, Feng J, Yu D, Huo Y, Ma X, Lam WH, Liu Z, Li XD, Ishibashi T, Dang S, Zhai Y. Synergism between CMG helicase and leading strand DNA polymerase at replication fork. Nat Commun 2023; 14:5849. [PMID: 37730685 PMCID: PMC10511561 DOI: 10.1038/s41467-023-41506-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 09/07/2023] [Indexed: 09/22/2023] Open
Abstract
The replisome that replicates the eukaryotic genome consists of at least three engines: the Cdc45-MCM-GINS (CMG) helicase that separates duplex DNA at the replication fork and two DNA polymerases, one on each strand, that replicate the unwound DNA. Here, we determined a series of cryo-electron microscopy structures of a yeast replisome comprising CMG, leading-strand polymerase Polε and three accessory factors on a forked DNA. In these structures, Polε engages or disengages with the motor domains of the CMG by occupying two alternative positions, which closely correlate with the rotational movement of the single-stranded DNA around the MCM pore. During this process, the polymerase remains stably coupled to the helicase using Psf1 as a hinge. This synergism is modulated by a concerted rearrangement of ATPase sites to drive DNA translocation. The Polε-MCM coupling is not only required for CMG formation to initiate DNA replication but also facilitates the leading-strand DNA synthesis mediated by Polε. Our study elucidates a mechanism intrinsic to the replisome that coordinates the activities of CMG and Polε to negotiate any roadblocks, DNA damage, and epigenetic marks encountered during translocation along replication forks.
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Affiliation(s)
- Zhichun Xu
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Jianrong Feng
- Division of Life Science, The Hong Kong University of Science & Technology, Hong Kong, China
| | - Daqi Yu
- Division of Life Science, The Hong Kong University of Science & Technology, Hong Kong, China
| | - Yunjing Huo
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Xiaohui Ma
- Division of Life Science, The Hong Kong University of Science & Technology, Hong Kong, China
| | - Wai Hei Lam
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Zheng Liu
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
| | - Xiang David Li
- Department of Chemistry, The University of Hong Kong, Hong Kong, China
| | - Toyotaka Ishibashi
- Division of Life Science, The Hong Kong University of Science & Technology, Hong Kong, China
| | - Shangyu Dang
- Division of Life Science, The Hong Kong University of Science & Technology, Hong Kong, China.
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China.
- HKUST-Shenzhen Research Institute, 518057, Nanshan, Shenzhen, China.
| | - Yuanliang Zhai
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China.
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