1
|
Zhang W, Wang Y, Liu Y, Liu C, Wang Y, He L, Cheng X, Peng Y, Xia L, Wu X, Wu J, Zhang Y, Sun L, Chen P, Li G, Tu Q, Liang J, Shang Y. NFIB facilitates replication licensing by acting as a genome organizer. Nat Commun 2023; 14:5076. [PMID: 37604829 PMCID: PMC10442334 DOI: 10.1038/s41467-023-40846-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 08/12/2023] [Indexed: 08/23/2023] Open
Abstract
The chromatin-based rule governing the selection and activation of replication origins in metazoans remains to be investigated. Here we report that NFIB, a member of Nuclear Factor I (NFI) family that was initially purified in host cells to promote adenoviral DNA replication but has since mainly been investigated in transcription regulation, is physically associated with the pre-replication complex (pre-RC) in mammalian cells. Genomic analyses reveal that NFIB facilitates the assembly of the pre-RC by increasing chromatin accessibility. Nucleosome binding and single-molecule magnetic tweezers shows that NFIB binds to and opens up nucleosomes. Transmission electron microscopy indicates that NFIB promotes nucleosome eviction on parental chromatin. NFIB deficiency leads to alterations of chromosome contacts/compartments in both G1 and S phase and affects the firing of a subset of origins at early-replication domains. Significantly, cancer-associated NFIB overexpression provokes gene duplication and genomic alterations recapitulating the genetic aberrance in clinical breast cancer and empowering cancer cells to dynamically evolve growth advantage and drug resistance. Together, these results point a role for NFIB in facilitating replication licensing by acting as a genome organizer, shedding new lights on the biological function of NFIB and on the replication origin selection in eukaryotes.
Collapse
Affiliation(s)
- Wenting Zhang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Yue Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121, China
| | - Yongjie Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Cuifang Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yizhou Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Lin He
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Xiao Cheng
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Yani Peng
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Lu Xia
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Xiaodi Wu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | - Jiajing Wu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | - Yu Zhang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Luyang Sun
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Ping Chen
- Department of Immunology, School of Basic Medical Sciences, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, 100069, China
| | - Guohong Li
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Qiang Tu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Jing Liang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China.
| | - Yongfeng Shang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China.
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, 311121, China.
| |
Collapse
|
2
|
Berger S, Chistol G. Visualizing the dynamics of DNA replication and repair at the single-molecule level. Methods Cell Biol 2023; 182:109-165. [PMID: 38359974 PMCID: PMC11246157 DOI: 10.1016/bs.mcb.2023.07.001] [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] [Indexed: 02/17/2024]
Abstract
During cell division, the genome of each eukaryotic cell is copied by thousands of replisomes-large protein complexes consisting of several dozen proteins. Recent studies suggest that the eukaryotic replisome is much more dynamic than previously thought. To directly visualize replisome dynamics in a physiological context, we recently developed a single-molecule approach for imaging replication proteins in Xenopus egg extracts. These extracts contain all the soluble nuclear proteins and faithfully recapitulate DNA replication and repair in vitro, serving as a powerful platform for studying the mechanisms of genome maintenance. Here we present detailed protocols for conducting single-molecule experiments in nuclear egg extracts and preparing key reagents. This workflow can be easily adapted to visualize the dynamics and function of other proteins implicated in DNA replication and repair.
Collapse
Affiliation(s)
- Scott Berger
- Biophysics Program, Stanford School of Medicine, Stanford, CA, United States
| | - Gheorghe Chistol
- Biophysics Program, Stanford School of Medicine, Stanford, CA, United States; Chemical and Systems Biology Department, Cancer Biology Program, Stanford School of Medicine, Stanford, CA, United States.
| |
Collapse
|
3
|
The small nonstructural protein NP1 of human bocavirus 1 directly interacts with Ku70 and RPA70 and facilitates viral DNA replication. PLoS Pathog 2022; 18:e1010578. [PMID: 35653410 PMCID: PMC9197078 DOI: 10.1371/journal.ppat.1010578] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 06/14/2022] [Accepted: 05/10/2022] [Indexed: 11/19/2022] Open
Abstract
Human bocavirus 1 (HBoV1), a member of the genus Bocaparvovirus of the family Parvoviridae, causes acute respiratory tract infections in young children. Well-differentiated pseudostratified human airway epithelium cultured at an air-liquid interface (HAE-ALI) is an ideal in vitro culture model to study HBoV1 infection. Unique to other parvoviruses, bocaparvoviruses express a small nonstructured protein NP1 of ~25 kDa from an open reading frame (ORF) in the center of the viral genome. NP1 plays an important role in viral DNA replication and pre-mRNA processing. In this study, we performed an affinity purification assay to identify HBoV1 NP1-inteacting proteins. We identified that Ku70 and RPA70 directly interact with the NP1 at a high binding affinity, characterized with an equilibrium dissociation constant (KD) of 95 nM and 122 nM, respectively. Furthermore, we mapped the key NP1-interacting domains of Ku70 at aa266-439 and of RPA70 at aa181-422. Following a dominant negative strategy, we revealed that the interactions of Ku70 and RPA70 with NP1 play a significant role in HBoV1 DNA replication not only in an in vitro viral DNA replication assay but also in HBoV1-infected HAE-ALI cultures. Collectively, our study revealed a novel mechanism by which HBoV1 NP1 enhances viral DNA replication through its direct interactions with Ku70 and RPA70.
Collapse
|
4
|
The large nonstructural protein (NS1) of the human bocavirus 1 (HBoV1) directly interacts with Ku70, which plays an important role in virus replication in human airway epithelia. J Virol 2021; 96:e0184021. [PMID: 34878919 PMCID: PMC8865542 DOI: 10.1128/jvi.01840-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Human bocavirus 1 (HBoV1), an autonomous human parvovirus, causes acute respiratory tract infections in young children. HBoV1 infects well-differentiated (polarized) human airway epithelium cultured at an air-liquid interface (HAE-ALI). HBoV1 expresses a large nonstructural protein, NS1, that is essential for viral DNA replication. HBoV1 infection of polarized human airway epithelial cells induces a DNA damage response (DDR) that is critical to viral DNA replication involving DNA repair with error-free Y-family DNA polymerases. HBoV1 NS1 or the isoform NS1-70 per se induces a DDR. In this study, using the second-generation proximity-dependent biotin identification (BioID2) approach, we identified that Ku70 is associated with the NS1-BioID2 pulldown complex through a direct interaction with NS1. Biolayer interferometry (BLI) assay determined a high binding affinity of NS1 with Ku70, which has an equilibrium dissociation constant (KD) value of 0.16 μM and processes the strongest interaction at the C-terminal domain. The association of Ku70 with NS1 was also revealed during HBoV1 infection of HAE-ALI. Knockdown of Ku70 and overexpression of the C-terminal domain of Ku70 significantly decreased HBoV1 replication in HAE-ALI. Thus, our study provides, for the first time, a direct interaction of parvovirus large nonstructural protein NS1 with Ku70. IMPORTANCE Parvovirus infection induces a DNA damage response (DDR) that plays a pivotal role in viral DNA replication. The DDR includes activation of ATM (ataxia telangiectasia mutated), ATR (ATM- and RAD3-related), and DNA-PKcs (DNA-dependent protein kinase catalytic subunit). The large nonstructural protein (NS1) often plays a role in the induction of DDR; however, how the DDR is induced during parvovirus infection or simply by the NS1 is not well studied. Activation of DNA-PKcs has been shown as one of the key DDR pathways in DNA replication of HBoV1. We identified that HBoV1 NS1 directly interacts with Ku70, but not Ku80, of the Ku70/Ku80 heterodimer at high affinity. This interaction is also important for HBoV1 replication in HAE-ALI. We propose that the interaction of NS1 with Ku70 recruits the Ku70/Ku80 complex to the viral DNA replication center, which activates DNA-PKcs and facilitates viral DNA replication.
Collapse
|
5
|
Behrmann MS, Perera HM, Hoang JM, Venkat TA, Visser BJ, Bates D, Trakselis MA. Targeted chromosomal Escherichia coli:dnaB exterior surface residues regulate DNA helicase behavior to maintain genomic stability and organismal fitness. PLoS Genet 2021; 17:e1009886. [PMID: 34767550 PMCID: PMC8612530 DOI: 10.1371/journal.pgen.1009886] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 11/24/2021] [Accepted: 10/18/2021] [Indexed: 12/05/2022] Open
Abstract
Helicase regulation involves modulation of unwinding speed to maintain coordination of DNA replication fork activities and is vital for replisome progression. Currently, mechanisms for helicase regulation that involve interactions with both DNA strands through a steric exclusion and wrapping (SEW) model and conformational shifts between dilated and constricted states have been examined in vitro. To better understand the mechanism and cellular impact of helicase regulation, we used CRISPR-Cas9 genome editing to study four previously identified SEW-deficient mutants of the bacterial replicative helicase DnaB. We discovered that these four SEW mutations stabilize constricted states, with more fully constricted mutants having a generally greater impact on genomic stress, suggesting a dynamic model for helicase regulation that involves both excluded strand interactions and conformational states. These dnaB mutations result in increased chromosome complexities, less stable genomes, and ultimately less viable and fit strains. Specifically, dnaB:mut strains present with increased mutational frequencies without significantly inducing SOS, consistent with leaving single-strand gaps in the genome during replication that are subsequently filled with lower fidelity. This work explores the genomic impacts of helicase dysregulation in vivo, supporting a combined dynamic regulatory mechanism involving a spectrum of DnaB conformational changes and relates current mechanistic understanding to functional helicase behavior at the replication fork. DNA replication is a vital biological process, and the proteins involved are structurally and functionally conserved across all domains of life. As our fundamental knowledge of genes and genetics grows, so does our awareness of links between acquired genetic mutations and disease. Understanding how genetic material is replicated accurately and efficiently and with high fidelity is the foundation to identifying and solving genome-based diseases. E. coli are model organisms, containing core replisome proteins, but lack the complexity of the human replication system, making them ideal for investigating conserved replisome behaviors. The helicase enzyme acts at the forefront of the replication fork to unwind the DNA helix and has also been shown to help coordinate other replisome functions. In this study, we examined specific mutations in the helicase that have been shown to regulate its conformation and speed of unwinding. We investigate how these mutations impact the growth, fitness, and cellular morphology of bacteria with the goal of understanding how helicase regulation mechanisms affect an organism’s ability to survive and maintain a stable genome.
Collapse
Affiliation(s)
- Megan S. Behrmann
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, United States of America
| | - Himasha M. Perera
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, United States of America
| | - Joy M. Hoang
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, United States of America
| | - Trisha A. Venkat
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, United States of America
| | - Bryan J. Visser
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - David Bates
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Michael A. Trakselis
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, United States of America
- * E-mail:
| |
Collapse
|
6
|
Determining translocation orientations of nucleic acid helicases. Methods 2021; 204:160-171. [PMID: 34758393 PMCID: PMC9076756 DOI: 10.1016/j.ymeth.2021.11.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 10/29/2021] [Accepted: 11/02/2021] [Indexed: 11/20/2022] Open
Abstract
Helicase enzymes translocate along an RNA or DNA template with a defined polarity to unwind, separate, or remodel duplex strands for a variety of genome maintenance processes. Helicase mutations are commonly associated with a variety of diseases including aging, cancer, and neurodegeneration. Biochemical characterization of these enzymes has provided a wealth of information on the kinetics of unwinding and substrate preferences, and several high-resolution structures of helicases alone and bound to oligonucleotides have been solved. Together, they provide mechanistic insights into the structural translocation and unwinding orientations of helicases. However, these insights rely on structural inferences derived from static snapshots. Instead, continued efforts should be made to combine structure and kinetics to better define active translocation orientations of helicases. This review explores many of the biochemical and biophysical methods utilized to map helicase binding orientation to DNA or RNA substrates and includes several time-dependent methods to unequivocally map the active translocation orientation of these enzymes to better define the active leading and trailing faces.
Collapse
|
7
|
The helicase core accessory regions of the phage BFK20 DnaB-like helicase gp43 significantly affect its activity, oligomeric state and DNA binding properties. Virology 2021; 558:96-109. [PMID: 33744744 DOI: 10.1016/j.virol.2021.02.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 02/23/2021] [Accepted: 02/28/2021] [Indexed: 11/23/2022]
Abstract
The multifunctional phage replication protein gp43 is composed of an N-terminal prim-pol domain and a C-terminal domain similar to the SF4-type replicative helicases. We prepared four mutants all missing the prim-pol domain with the helicase core flanked by accessory N- and C-terminal regions truncated to varying extents. The shortest fragment still possessing strong ssDNA-dependent ATPase activity and helicase activity was gp43HEL519-983. The other proteins tested were gp43HEL557-983, gp43HEL519-855 and gp43HEL519-896. Removal of the 38 N-terminal residues in gp43HEL557-983, or the 128 and 87 C-terminal residues in gp43HEL519-855 and gp43HEL519-896, resulted in a significant decrease in the ATPase activities. The 38-amino acid N-terminal region has probably a function in modulating DNA binding and protein oligomerization. Deletion of the 87 C-terminal residues resulted in a twofold increase in the unwinding rate. This region is likely indispensable for binding to DNA substrates.
Collapse
|
8
|
Abstract
In all cell types, a multi-protein machinery is required to accurately duplicate the large duplex DNA genome. This central life process requires five core replisome factors in all cellular life forms studied thus far. Unexpectedly, three of the five core replisome factors have no common ancestor between bacteria and eukaryotes. Accordingly, the replisome machines of bacteria and eukaryotes have important distinctions in the way that they are organized and function. This chapter outlines the major replication proteins that perform DNA duplication at replication forks, with particular attention to differences and similarities in the strategies used by eukaryotes and bacteria.
Collapse
Affiliation(s)
- Nina Y Yao
- DNA Replication Laboratory, The Rockefeller University, New York, USA, 10065
| | - Michael E O'Donnell
- DNA Replication Laboratory, The Rockefeller University, New York, USA, 10065. .,Howard Hughes Medical Institute, The Rockefeller University, New York, USA, 10065.
| |
Collapse
|
9
|
Kose HB, Xie S, Cameron G, Strycharska MS, Yardimci H. Duplex DNA engagement and RPA oppositely regulate the DNA-unwinding rate of CMG helicase. Nat Commun 2020; 11:3713. [PMID: 32709841 PMCID: PMC7382467 DOI: 10.1038/s41467-020-17443-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 07/01/2020] [Indexed: 01/09/2023] Open
Abstract
A ring-shaped helicase unwinds DNA during chromosome replication in all organisms. Replicative helicases generally unwind duplex DNA an order of magnitude slower compared to their in vivo replication fork rates. However, the origin of slow DNA unwinding rates by replicative helicases and the mechanism by which other replication components increase helicase speed are unclear. Here, we demonstrate that engagement of the eukaryotic CMG helicase with template DNA at the replication fork impairs its helicase activity, which is alleviated by binding of the single-stranded DNA binding protein, RPA, to the excluded DNA strand. Intriguingly, we found that, when stalled due to interaction with the parental duplex, DNA rezipping-induced helicase backtracking reestablishes productive helicase-fork engagement, underscoring the significance of plasticity in helicase action. Our work provides a mechanistic basis for relatively slow duplex unwinding by replicative helicases and explains how replisome components that interact with the excluded DNA strand stimulate fork rates.
Collapse
Affiliation(s)
- Hazal B Kose
- Single Molecule Imaging of Genome Duplication and Maintenance Laboratory, The Francis Crick Institute, NW1 1AT, London, UK
| | - Sherry Xie
- Single Molecule Imaging of Genome Duplication and Maintenance Laboratory, The Francis Crick Institute, NW1 1AT, London, UK
| | - George Cameron
- Single Molecule Imaging of Genome Duplication and Maintenance Laboratory, The Francis Crick Institute, NW1 1AT, London, UK
| | - Melania S Strycharska
- Single Molecule Imaging of Genome Duplication and Maintenance Laboratory, The Francis Crick Institute, NW1 1AT, London, UK
| | - Hasan Yardimci
- Single Molecule Imaging of Genome Duplication and Maintenance Laboratory, The Francis Crick Institute, NW1 1AT, London, UK.
| |
Collapse
|
10
|
Wiegand T. A solid-state NMR tool box for the investigation of ATP-fueled protein engines. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2020; 117:1-32. [PMID: 32471533 DOI: 10.1016/j.pnmrs.2020.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 02/18/2020] [Accepted: 02/20/2020] [Indexed: 06/11/2023]
Abstract
Motor proteins are involved in a variety of cellular processes. Their main purpose is to convert the chemical energy released during adenosine triphosphate (ATP) hydrolysis into mechanical work. In this review, solid-state Nuclear Magnetic Resonance (NMR) approaches are discussed allowing studies of structures, conformational events and dynamic features of motor proteins during a variety of enzymatic reactions. Solid-state NMR benefits from straightforward sample preparation based on sedimentation of the proteins directly into the Magic-Angle Spinning (MAS) rotor. Protein resonance assignment is the crucial and often time-limiting step in interpreting the wealth of information encoded in the NMR spectra. Herein, potentials, challenges and limitations in resonance assignment for large motor proteins are presented, focussing on both biochemical and spectroscopic approaches. This work highlights NMR tools available to study the action of the motor domain and its coupling to functional processes, as well as to identify protein-nucleotide interactions during events such as DNA replication. Arrested protein states of reaction coordinates such as ATP hydrolysis can be trapped for NMR studies by using stable, non-hydrolysable ATP analogues that mimic the physiological relevant states as accurately as possible. Recent advances in solid-state NMR techniques ranging from Dynamic Nuclear Polarization (DNP), 31P-based heteronuclear correlation experiments, 1H-detected spectra at fast MAS frequencies >100 kHz to paramagnetic NMR are summarized and their applications to the bacterial DnaB helicase from Helicobacter pylori are discussed.
Collapse
Affiliation(s)
- Thomas Wiegand
- Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland.
| |
Collapse
|
11
|
Brosh RM, Matson SW. History of DNA Helicases. Genes (Basel) 2020; 11:genes11030255. [PMID: 32120966 PMCID: PMC7140857 DOI: 10.3390/genes11030255] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/18/2020] [Accepted: 02/20/2020] [Indexed: 12/13/2022] Open
Abstract
Since the discovery of the DNA double helix, there has been a fascination in understanding the molecular mechanisms and cellular processes that account for: (i) the transmission of genetic information from one generation to the next and (ii) the remarkable stability of the genome. Nucleic acid biologists have endeavored to unravel the mysteries of DNA not only to understand the processes of DNA replication, repair, recombination, and transcription but to also characterize the underlying basis of genetic diseases characterized by chromosomal instability. Perhaps unexpectedly at first, DNA helicases have arisen as a key class of enzymes to study in this latter capacity. From the first discovery of ATP-dependent DNA unwinding enzymes in the mid 1970's to the burgeoning of helicase-dependent pathways found to be prevalent in all kingdoms of life, the story of scientific discovery in helicase research is rich and informative. Over four decades after their discovery, we take this opportunity to provide a history of DNA helicases. No doubt, many chapters are left to be written. Nonetheless, at this juncture we are privileged to share our perspective on the DNA helicase field - where it has been, its current state, and where it is headed.
Collapse
Affiliation(s)
- Robert M. Brosh
- Section on DNA Helicases, Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
- Correspondence: (R.M.B.J.); (S.W.M.); Tel.: +1-410-558-8578 (R.M.B.J.); +1-919-962-0005 (S.W.M.)
| | - Steven W. Matson
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Correspondence: (R.M.B.J.); (S.W.M.); Tel.: +1-410-558-8578 (R.M.B.J.); +1-919-962-0005 (S.W.M.)
| |
Collapse
|
12
|
Perera HM, Behrmann MS, Hoang JM, Griffin WC, Trakselis MA. Contacts and context that regulate DNA helicase unwinding and replisome progression. Enzymes 2019; 45:183-223. [PMID: 31627877 DOI: 10.1016/bs.enz.2019.08.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hexameric DNA helicases involved in the separation of duplex DNA at the replication fork have a universal architecture but have evolved from two separate protein families. The consequences are that the regulation, translocation polarity, strand specificity, and architectural orientation varies between phage/bacteria to that of archaea/eukaryotes. Once assembled and activated for single strand DNA translocation and unwinding, the DNA polymerase couples tightly to the helicase forming a robust replisome complex. However, this helicase-polymerase interaction can be challenged by various forms of endogenous or exogenous agents that can stall the entire replisome or decouple DNA unwinding from synthesis. The consequences of decoupling can be severe, leading to a build-up of ssDNA requiring various pathways for replication fork restart. All told, the hexameric helicase sits prominently at the front of the replisome constantly responding to a variety of obstacles that require transient unwinding/reannealing, traversal of more stable blocks, and alternations in DNA unwinding speed that regulate replisome progression.
Collapse
Affiliation(s)
- Himasha M Perera
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Megan S Behrmann
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Joy M Hoang
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Wezley C Griffin
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States
| | - Michael A Trakselis
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, United States.
| |
Collapse
|
13
|
Nero TM, Dalia TN, Wang JCY, Kysela DT, Bochman ML, Dalia AB. ComM is a hexameric helicase that promotes branch migration during natural transformation in diverse Gram-negative species. Nucleic Acids Res 2019; 46:6099-6111. [PMID: 29722872 PMCID: PMC6158740 DOI: 10.1093/nar/gky343] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 04/19/2018] [Indexed: 12/16/2022] Open
Abstract
Acquisition of foreign DNA by natural transformation is an important mechanism of adaptation and evolution in diverse microbial species. Here, we characterize the mechanism of ComM, a broadly conserved AAA+ protein previously implicated in homologous recombination of transforming DNA (tDNA) in naturally competent Gram-negative bacterial species. In vivo, we found that ComM was required for efficient comigration of linked genetic markers in Vibrio cholerae and Acinetobacter baylyi, which is consistent with a role in branch migration. Also, ComM was particularly important for integration of tDNA with increased sequence heterology, suggesting that its activity promotes the acquisition of novel DNA sequences. In vitro, we showed that purified ComM binds ssDNA, oligomerizes into a hexameric ring, and has bidirectional helicase and branch migration activity. Based on these data, we propose a model for tDNA integration during natural transformation. This study provides mechanistic insight into the enigmatic steps involved in tDNA integration and uncovers the function of a protein required for this conserved mechanism of horizontal gene transfer.
Collapse
Affiliation(s)
- Thomas M Nero
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Triana N Dalia
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | | | - David T Kysela
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Matthew L Bochman
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA
| | - Ankur B Dalia
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| |
Collapse
|
14
|
Burnham DR, Kose HB, Hoyle RB, Yardimci H. The mechanism of DNA unwinding by the eukaryotic replicative helicase. Nat Commun 2019; 10:2159. [PMID: 31089141 PMCID: PMC6517413 DOI: 10.1038/s41467-019-09896-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 04/05/2019] [Indexed: 12/18/2022] Open
Abstract
Accurate DNA replication is tightly regulated in eukaryotes to ensure genome stability during cell division and is performed by the multi-protein replisome. At the core an AAA+ hetero-hexameric complex, Mcm2-7, together with GINS and Cdc45 form the active replicative helicase Cdc45/Mcm2-7/GINS (CMG). It is not clear how this replicative ring helicase translocates on, and unwinds, DNA. We measure real-time dynamics of purified recombinant Drosophila melanogaster CMG unwinding DNA with single-molecule magnetic tweezers. Our data demonstrates that CMG exhibits a biased random walk, not the expected unidirectional motion. Through building a kinetic model we find CMG may enter up to three paused states rather than unwinding, and should these be prevented, in vivo fork rates would be recovered in vitro. We propose a mechanism in which CMG couples ATP hydrolysis to unwinding by acting as a lazy Brownian ratchet, thus providing quantitative understanding of the central process in eukaryotic DNA replication.
Collapse
Affiliation(s)
- Daniel R Burnham
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Hazal B Kose
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Rebecca B Hoyle
- School of Mathematical Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Hasan Yardimci
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
| |
Collapse
|
15
|
Kose HB, Larsen NB, Duxin JP, Yardimci H. Dynamics of the Eukaryotic Replicative Helicase at Lagging-Strand Protein Barriers Support the Steric Exclusion Model. Cell Rep 2019; 26:2113-2125.e6. [PMID: 30784593 PMCID: PMC6381796 DOI: 10.1016/j.celrep.2019.01.086] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 12/19/2018] [Accepted: 01/24/2019] [Indexed: 12/01/2022] Open
Abstract
Progression of DNA replication depends on the ability of the replisome complex to overcome nucleoprotein barriers. During eukaryotic replication, the CMG helicase translocates along the leading-strand template and unwinds the DNA double helix. While proteins bound to the leading-strand template efficiently block the helicase, the impact of lagging-strand protein obstacles on helicase translocation and replisome progression remains controversial. Here, we show that CMG and replisome progressions are impaired when proteins crosslinked to the lagging-strand template enhance the stability of duplex DNA. In contrast, proteins that exclusively interact with the lagging-strand template influence neither the translocation of isolated CMG nor replisome progression in Xenopus egg extracts. Our data imply that CMG completely excludes the lagging-strand template from the helicase central channel while unwinding DNA at the replication fork, which clarifies how two CMG helicases could freely cross one another during replication initiation and termination.
Collapse
Affiliation(s)
- Hazal B Kose
- Single Molecule Imaging of Genome Duplication and Maintenance Laboratory, The Francis Crick Institute, NW1 1AT London, UK
| | - Nicolai B Larsen
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Julien P Duxin
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Hasan Yardimci
- Single Molecule Imaging of Genome Duplication and Maintenance Laboratory, The Francis Crick Institute, NW1 1AT London, UK.
| |
Collapse
|
16
|
Li H, O'Donnell ME. The Eukaryotic CMG Helicase at the Replication Fork: Emerging Architecture Reveals an Unexpected Mechanism. Bioessays 2018; 40. [PMID: 29405332 DOI: 10.1002/bies.201700208] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 12/27/2017] [Indexed: 01/12/2023]
Abstract
The eukaryotic helicase is an 11-subunit machine containing an Mcm2-7 motor ring that encircles DNA, Cdc45 and the GINS tetramer, referred to as CMG (Cdc45, Mcm2-7, GINS). CMG is "built" on DNA at origins in two steps. First, two Mcm2-7 rings are assembled around duplex DNA at origins in G1 phase, forming the Mcm2-7 "double hexamer." In a second step, in S phase Cdc45 and GINS are assembled onto each Mcm2-7 ring, hence producing two CMGs that ultimately form two replication forks that travel in opposite directions. Here, we review recent findings about CMG structure and function. The CMG unwinds the parental duplex and is also the organizing center of the replisome: it binds DNA polymerases and other factors. EM studies reveal a 20-subunit core replisome with the leading Pol ϵ and lagging Pol α-primase on opposite faces of CMG, forming a fundamentally asymmetric architecture. Structural studies of CMG at a replication fork reveal unexpected details of how CMG engages the DNA fork. The structures of CMG and the Mcm2-7 double hexamer on DNA suggest a completely unanticipated process for formation of bidirectional replication forks at origins.
Collapse
Affiliation(s)
- Huilin Li
- Cryo-EM Structural Biology Laboratory, Van Andel Research Institute, Grand Rapids, MI 49503, USA
| | - Michael E O'Donnell
- Department of DNA Replication, Rockefeller University and HHMI, New York, NY 10065, USA
| |
Collapse
|
17
|
The ring-shaped hexameric helicases that function at DNA replication forks. Nat Struct Mol Biol 2018; 25:122-130. [PMID: 29379175 DOI: 10.1038/s41594-018-0024-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 11/27/2017] [Indexed: 11/08/2022]
Abstract
DNA replication requires separation of genomic duplex DNA strands, an operation that is performed by a hexameric ring-shaped helicase in all domains of life. The structures and chemomechanical actions of these fascinating machines are coming into sharper focus. Although there is no evolutionary relationship between the hexameric helicases of bacteria and those of archaea and eukaryotes, they share many fundamental features. Here we review recent studies of these two groups of hexameric helicases and the unexpected distinctions they have also unveiled.
Collapse
|
18
|
Perez-Arnaiz P, Bruck I, Colbert MK, Kaplan DL. An intact Mcm10 coiled-coil interaction surface is important for origin melting, helicase assembly and the recruitment of Pol-α to Mcm2-7. Nucleic Acids Res 2017; 45:7261-7275. [PMID: 28510759 PMCID: PMC5499591 DOI: 10.1093/nar/gkx438] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 05/03/2017] [Indexed: 11/16/2022] Open
Abstract
Mcm10 is an essential eukaryotic factor required for DNA replication. The replication fork helicase is composed of Cdc45, Mcm2–7 and GINS (CMG). DDK is an S-phase-specific kinase required for replication initiation, and the DNA primase-polymerase in eukaryotes is pol α. Mcm10 forms oligomers in vitro, mediated by the coiled-coil domain at the N-terminal region of the protein. We characterized an Mcm10 mutant at the N-terminal Domain (NTD), Mcm10-4A, defective for self-interaction. We found that the Mcm10-4A mutant was defective for stimulating DDK phosphorylation of Mcm2, binding to eighty-nucleotide ssDNA, and recruiting pol α to Mcm2–7 in vitro. Expression of wild-type levels of mcm10-4A resulted in severe growth and DNA replication defects in budding yeast cells, with diminished DDK phosphorylation of Mcm2. We then expressed the mcm10-4A in mcm5-bob1 mutant cells to bypass the defects mediated by diminished stimulation of DDK phosphorylation of Mcm2. Expression of wild-type levels of mcm10-4A in mcm5-bob1 mutant cells resulted in severe growth and DNA replication defects, along with diminished RPA signal at replication origins. We also detected diminished GINS and pol-α recruitment to the Mcm2–7 complex. We conclude that an intact Mcm10 coiled-coil interaction surface is important for origin melting, helicase assembly, and the recruitment of pol α to Mcm2–7.
Collapse
Affiliation(s)
- Patricia Perez-Arnaiz
- Florida State University College of Medicine, Department of Biomedical Sciences, Tallahassee, FL 32306, USA
| | - Irina Bruck
- Florida State University College of Medicine, Department of Biomedical Sciences, Tallahassee, FL 32306, USA
| | - Max K Colbert
- Florida State University College of Medicine, Department of Biomedical Sciences, Tallahassee, FL 32306, USA
| | - Daniel L Kaplan
- Florida State University College of Medicine, Department of Biomedical Sciences, Tallahassee, FL 32306, USA
| |
Collapse
|
19
|
Strobel EJ, Watters KE, Nedialkov Y, Artsimovitch I, Lucks JB. Distributed biotin-streptavidin transcription roadblocks for mapping cotranscriptional RNA folding. Nucleic Acids Res 2017; 45:e109. [PMID: 28398514 PMCID: PMC5499547 DOI: 10.1093/nar/gkx233] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 04/02/2017] [Indexed: 01/24/2023] Open
Abstract
RNA folding during transcription directs an order of folding that can determine RNA structure and function. However, the experimental study of cotranscriptional RNA folding has been limited by the lack of easily approachable methods that can interrogate nascent RNA structure at nucleotide resolution. To address this, we previously developed cotranscriptional selective 2΄-hydroxyl acylation analyzed by primer extension sequencing (SHAPE-Seq) to simultaneously probe all intermediate RNA transcripts during transcription by stalling elongation complexes at catalytically dead EcoRIE111Q roadblocks. While effective, the distribution of elongation complexes using EcoRIE111Q requires laborious PCR using many different oligonucleotides for each sequence analyzed. Here, we improve the broad applicability of cotranscriptional SHAPE-Seq by developing a sequence-independent biotin-streptavidin (SAv) roadblocking strategy that simplifies the preparation of roadblocking DNA templates. We first determine the properties of biotin-SAv roadblocks. We then show that randomly distributed biotin-SAv roadblocks can be used in cotranscriptional SHAPE-Seq experiments to identify the same RNA structural transitions related to a riboswitch decision-making process that we previously identified using EcoRIE111Q. Lastly, we find that EcoRIE111Q maps nascent RNA structure to specific transcript lengths more precisely than biotin-SAv and propose guidelines to leverage the complementary strengths of each transcription roadblock in cotranscriptional SHAPE-Seq.
Collapse
Affiliation(s)
- Eric J. Strobel
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60201, USA
| | - Kyle E. Watters
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Yuri Nedialkov
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
- The Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Irina Artsimovitch
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
- The Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Julius B. Lucks
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60201, USA
- To whom correspondence should be addressed. Tel: +1 847 467 2943; Fax: +1 847 491 3728;
| |
Collapse
|
20
|
Langston LD, Mayle R, Schauer GD, Yurieva O, Zhang D, Yao NY, Georgescu RE, O'Donnell ME. Mcm10 promotes rapid isomerization of CMG-DNA for replisome bypass of lagging strand DNA blocks. eLife 2017; 6:e29118. [PMID: 28869037 PMCID: PMC5599239 DOI: 10.7554/elife.29118] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 09/03/2017] [Indexed: 12/18/2022] Open
Abstract
Replicative helicases in all cell types are hexameric rings that unwind DNA by steric exclusion in which the helicase encircles the tracking strand only and excludes the other strand from the ring. This mode of translocation allows helicases to bypass blocks on the strand that is excluded from the central channel. Unlike other replicative helicases, eukaryotic CMG helicase partially encircles duplex DNA at a forked junction and is stopped by a block on the non-tracking (lagging) strand. This report demonstrates that Mcm10, an essential replication protein unique to eukaryotes, binds CMG and greatly stimulates its helicase activity in vitro. Most significantly, Mcm10 enables CMG and the replisome to bypass blocks on the non-tracking DNA strand. We demonstrate that bypass occurs without displacement of the blocks and therefore Mcm10 must isomerize the CMG-DNA complex to achieve the bypass function.
Collapse
Affiliation(s)
- Lance D Langston
- The Rockefeller UniversityNew YorkUnited States
- Howard Hughes Medical InstituteNew YorkUnited States
| | - Ryan Mayle
- The Rockefeller UniversityNew YorkUnited States
- Howard Hughes Medical InstituteNew YorkUnited States
| | | | - Olga Yurieva
- The Rockefeller UniversityNew YorkUnited States
- Howard Hughes Medical InstituteNew YorkUnited States
| | | | - Nina Y Yao
- The Rockefeller UniversityNew YorkUnited States
| | - Roxana E Georgescu
- The Rockefeller UniversityNew YorkUnited States
- Howard Hughes Medical InstituteNew YorkUnited States
| | - Mike E O'Donnell
- The Rockefeller UniversityNew YorkUnited States
- Howard Hughes Medical InstituteNew YorkUnited States
| |
Collapse
|
21
|
Abstract
Genome duplication is carried out by pairs of replication forks that assemble at origins of replication and then move in opposite directions. DNA replication ends when converging replication forks meet. During this process, which is known as replication termination, DNA synthesis is completed, the replication machinery is disassembled and daughter molecules are resolved. In this Review, we outline the steps that are likely to be common to replication termination in most organisms, namely, fork convergence, synthesis completion, replisome disassembly and decatenation. We briefly review the mechanism of termination in the bacterium Escherichia coli and in simian virus 40 (SV40) and also focus on recent advances in eukaryotic replication termination. In particular, we discuss the recently discovered E3 ubiquitin ligases that control replisome disassembly in yeast and higher eukaryotes, and how their activity is regulated to avoid genome instability.
Collapse
|
22
|
Tatsumi R, Ishimi Y. An MCM4 mutation detected in cancer cells affects MCM4/6/7 complex formation. J Biochem 2017; 161:259-268. [PMID: 27794528 DOI: 10.1093/jb/mvw065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/20/2016] [Indexed: 02/01/2023] Open
Abstract
An MCM4 mutation detected in human cancer cells from endometrium was characterized. The mutation of G486D is located within MCM-box and the glycine at 486 in human MCM4 is conserved in Saccharomyces cerevisiae MCM4 and Sulfolobus solfataricus MCM. This MCM4 mutation affected human MCM4/6/7 complex formation, since the complex containing the mutant MCM4 protein is unstable and the mutant MCM4 protein is tend to be degraded. It is likely that the MCM4 mutation affects the interaction with MCM7 to destabilize the MCM4/6/7 complex. Cells with abnormal nuclear morphology were detected when the mutant MCM4 was expressed in HeLa cells, suggesting that DNA replication was perturbed in the presence of the mutant MCM4. Role of the conserved amino acid in MCM4 function is discussed.
Collapse
|
23
|
Langston L, O'Donnell M. Action of CMG with strand-specific DNA blocks supports an internal unwinding mode for the eukaryotic replicative helicase. eLife 2017; 6. [PMID: 28346143 PMCID: PMC5381960 DOI: 10.7554/elife.23449] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Accepted: 03/23/2017] [Indexed: 12/16/2022] Open
Abstract
Replicative helicases are ring-shaped hexamers that encircle DNA for duplex unwinding. The currently accepted view of hexameric helicase function is by steric exclusion, where the helicase encircles one DNA strand and excludes the other, acting as a wedge with an external DNA unwinding point during translocation. Accordingly, strand-specific blocks only affect these helicases when placed on the tracking strand, not the excluded strand. We examined the effect of blocks on the eukaryotic CMG and, contrary to expectations, blocks on either strand inhibit CMG unwinding. A recent cryoEM structure of yeast CMG shows that duplex DNA enters the helicase and unwinding occurs in the central channel. The results of this report inform important aspects of the structure, and we propose that CMG functions by a modified steric exclusion process in which both strands enter the helicase and the duplex unwinding point is internal, followed by exclusion of the non-tracking strand. DOI:http://dx.doi.org/10.7554/eLife.23449.001
Collapse
Affiliation(s)
- Lance Langston
- Howard Hughes Medical Institute, The Rockefeller University, New York City, United States
| | - Mike O'Donnell
- Howard Hughes Medical Institute, The Rockefeller University, New York City, United States
| |
Collapse
|
24
|
Dewar JM, Low E, Mann M, Räschle M, Walter JC. CRL2 Lrr1 promotes unloading of the vertebrate replisome from chromatin during replication termination. Genes Dev 2017; 31:275-290. [PMID: 28235849 PMCID: PMC5358724 DOI: 10.1101/gad.291799.116] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Accepted: 01/30/2017] [Indexed: 01/26/2023]
Abstract
Here, Dewar et al. use a proteomic screen in Xenopus egg extracts to identify factors that are enriched on chromatin when CMG unloading from chromatin, which is a key event during eukaryotic replication termination, is blocked. Their results show that CRL2Lrr1 is a master regulator of replisome disassembly during vertebrate DNA replication termination. A key event during eukaryotic replication termination is the removal of the CMG helicase from chromatin. CMG unloading involves ubiquitylation of its Mcm7 subunit and the action of the p97 ATPase. Using a proteomic screen in Xenopus egg extracts, we identified factors that are enriched on chromatin when CMG unloading is blocked. This approach identified the E3 ubiquitin ligase CRL2Lrr1, a specific p97 complex, other potential regulators of termination, and many replisome components. We show that Mcm7 ubiquitylation and CRL2Lrr1 binding to chromatin are temporally linked and occur only during replication termination. In the absence of CRL2Lrr1, Mcm7 is not ubiquitylated, CMG unloading is inhibited, and a large subcomplex of the vertebrate replisome that includes DNA Pol ε is retained on DNA. Our data identify CRL2Lrr1 as a master regulator of replisome disassembly during vertebrate DNA replication termination.
Collapse
Affiliation(s)
- James M Dewar
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Emily Low
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Matthias Mann
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Markus Räschle
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.,Howard Hughes Medical Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| |
Collapse
|
25
|
Parker MW, Botchan MR, Berger JM. Mechanisms and regulation of DNA replication initiation in eukaryotes. Crit Rev Biochem Mol Biol 2017; 52:107-144. [PMID: 28094588 DOI: 10.1080/10409238.2016.1274717] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cellular DNA replication is initiated through the action of multiprotein complexes that recognize replication start sites in the chromosome (termed origins) and facilitate duplex DNA melting within these regions. In a typical cell cycle, initiation occurs only once per origin and each round of replication is tightly coupled to cell division. To avoid aberrant origin firing and re-replication, eukaryotes tightly regulate two events in the initiation process: loading of the replicative helicase, MCM2-7, onto chromatin by the origin recognition complex (ORC), and subsequent activation of the helicase by its incorporation into a complex known as the CMG. Recent work has begun to reveal the details of an orchestrated and sequential exchange of initiation factors on DNA that give rise to a replication-competent complex, the replisome. Here, we review the molecular mechanisms that underpin eukaryotic DNA replication initiation - from selecting replication start sites to replicative helicase loading and activation - and describe how these events are often distinctly regulated across different eukaryotic model organisms.
Collapse
Affiliation(s)
- Matthew W Parker
- a Department of Biophysics and Biophysical Chemistry , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Michael R Botchan
- b Department of Molecular and Cell Biology , University of California Berkeley , Berkeley , CA , USA
| | - James M Berger
- a Department of Biophysics and Biophysical Chemistry , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| |
Collapse
|
26
|
Kelly T. Historical Perspective of Eukaryotic DNA Replication. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:1-41. [PMID: 29357051 DOI: 10.1007/978-981-10-6955-0_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The replication of the genome of a eukaryotic cell is a complex process requiring the ordered assembly of multiprotein replisomes at many chromosomal sites. The process is strictly controlled during the cell cycle to ensure the complete and faithful transmission of genetic information to progeny cells. Our current understanding of the mechanisms of eukaryotic DNA replication has evolved over a period of more than 30 years through the efforts of many investigators. The aim of this perspective is to provide a brief history of the major advances during this period.
Collapse
Affiliation(s)
- Thomas Kelly
- Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
| |
Collapse
|
27
|
Abstract
The machinery at the eukaryotic replication fork has seen many new structural advances using electron microscopy and crystallography. Recent structures of eukaryotic replisome components include the Mcm2-7 complex, the CMG helicase, DNA polymerases, a Ctf4 trimer hub and the first look at a core replisome of 20 different proteins containing the helicase, primase, leading polymerase and a lagging strand polymerase. The eukaryotic core replisome shows an unanticipated architecture, with one polymerase sitting above the helicase and the other below. Additionally, structures of Mcm2 bound to an H3/H4 tetramer suggest a direct role of the replisome in handling nucleosomes, which are important to DNA organization and gene regulation. This review provides a summary of some of the many recent advances in the structure of the eukaryotic replisome.
Collapse
Affiliation(s)
- Mike O'Donnell
- DNA Replication Lab, The Rockefeller University, 1230 York Avenue, New York, New York, USA; Howard Hughes Medical Institute.
| | - Huilin Li
- Department of Biochemistry & Cell Biology, Stony Brook University, Stony Brook, New York, USA; Biology Department, Brookhaven National Laboratory, Upton, New York, USA.
| |
Collapse
|
28
|
The excluded DNA strand is SEW important for hexameric helicase unwinding. Methods 2016; 108:79-91. [DOI: 10.1016/j.ymeth.2016.04.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 04/07/2016] [Accepted: 04/07/2016] [Indexed: 02/04/2023] Open
|
29
|
Juríková M, Danihel Ľ, Polák Š, Varga I. Ki67, PCNA, and MCM proteins: Markers of proliferation in the diagnosis of breast cancer. Acta Histochem 2016; 118:544-52. [PMID: 27246286 DOI: 10.1016/j.acthis.2016.05.002] [Citation(s) in RCA: 394] [Impact Index Per Article: 49.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 04/05/2016] [Accepted: 05/16/2016] [Indexed: 12/22/2022]
Abstract
The proliferative activity of tumour cells represents an important prognostic marker in the diagnosis of cancer. One of the methods for assessing the proliferative activity of cells is the immunohistochemical detection of cell cycle-specific antigens. For example, Ki67, proliferating cell nuclear antigen (PCNA), and minichromosome maintenance (MCM) proteins are standard markers of proliferation that are commonly used to assess the growth fraction of a cell population. The function of Ki67, the widely used marker of proliferation, still remains unclear. In contrast, PCNA and MCM proteins have been identified as important participants of DNA replication. All three proteins only manifest their expression during the cell division of normal and neoplastic cells. Since the expression of these proliferative markers was confirmed in several malignant tumours, their prognostic and predictive values have been evaluated to determine their significance in the diagnosis of cancer. This review offers insight into the discovery of the abovementioned proteins, as well as their current molecular and biological importance. In addition, the functions and properties of all three proteins and their use as markers of proliferation in the diagnosis of breast cancer are described. This work also reveals new findings about the role of Ki67 during the mitotic phase of the cell cycle. Finally, information is provided about the advantages and disadvantages of using all three antigens in the diagnosis of cancer.
Collapse
Affiliation(s)
- Miroslava Juríková
- Institute of Histology and Embryology, Faculty of Medicine, Comenius University in Bratislava, Špitálska 24, 813 72 Bratislava, Slovakia.
| | - Ľudovít Danihel
- Institute of Pathological Anatomy, Faculty of Medicine, Comenius University in Bratislava, Špitálska 24, 813 72 Bratislava, Slovakia
| | - Štefan Polák
- Institute of Histology and Embryology, Faculty of Medicine, Comenius University in Bratislava, Špitálska 24, 813 72 Bratislava, Slovakia
| | - Ivan Varga
- Institute of Histology and Embryology, Faculty of Medicine, Comenius University in Bratislava, Špitálska 24, 813 72 Bratislava, Slovakia
| |
Collapse
|
30
|
Abstract
The cellular replicating machine, or "replisome," is composed of numerous different proteins. The core replication proteins in all cell types include a helicase, primase, DNA polymerases, sliding clamp, clamp loader, and single-strand binding (SSB) protein. The core eukaryotic replisome proteins evolved independently from those of bacteria and thus have distinct architectures and mechanisms of action. The core replisome proteins of the eukaryote include: an 11-subunit CMG helicase, DNA polymerase alpha-primase, leading strand DNA polymerase epsilon, lagging strand DNA polymerase delta, PCNA clamp, RFC clamp loader, and the RPA SSB protein. There are numerous other proteins that travel with eukaryotic replication forks, some of which are known to be involved in checkpoint regulation or nucleosome handling, but most have unknown functions and no bacterial analogue. Recent studies have revealed many structural and functional insights into replisome action. Also, the first structure of a replisome from any cell type has been elucidated for a eukaryote, consisting of 20 distinct proteins, with quite unexpected results. This review summarizes the current state of knowledge of the eukaryotic core replisome proteins, their structure, individual functions, and how they are organized at the replication fork as a machine.
Collapse
Affiliation(s)
- D Zhang
- The Rockefeller University, New York, NY, United States
| | - M O'Donnell
- The Rockefeller University, New York, NY, United States; Howard Hughes Medical Institute, The Rockefeller University, New York, NY, United States.
| |
Collapse
|
31
|
Deegan TD, Diffley JFX. MCM: one ring to rule them all. Curr Opin Struct Biol 2016; 37:145-51. [PMID: 26866665 DOI: 10.1016/j.sbi.2016.01.014] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 01/26/2016] [Accepted: 01/26/2016] [Indexed: 11/25/2022]
Abstract
Precise replication of the eukaryotic genome is achieved primarily through strict regulation of the enzyme responsible for DNA unwinding, the replicative helicase. The motor of this helicase is a hexameric AAA+ ATPase called MCM. The loading of MCM onto DNA and its subsequent activation and disassembly are each restricted to separate cell cycle phases; this ensures that a functional replisome is only built once at any replication origin. In recent years, biochemical and structural studies have shown that distinct conformational changes in MCM, each requiring post-translational modifications and/or the activity of other replication proteins, define the various stages of the chromosome replication cycle. Here, we review recent progress in this area.
Collapse
Affiliation(s)
- Tom D Deegan
- The Francis Crick Institute, Clare Hall Laboratory, South Mimms, Herts EN6 3LD, United Kingdom
| | - John F X Diffley
- The Francis Crick Institute, Clare Hall Laboratory, South Mimms, Herts EN6 3LD, United Kingdom.
| |
Collapse
|
32
|
The role of ATP-dependent machines in regulating genome topology. Curr Opin Struct Biol 2016; 36:85-96. [PMID: 26827284 DOI: 10.1016/j.sbi.2016.01.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 01/08/2016] [Accepted: 01/12/2016] [Indexed: 11/22/2022]
Abstract
All cells must copy and express genes in accord with internal and external cues. The proper timing and response of such events relies on the active control of higher-order genomic organization. Cells use ATP-dependent molecular machines to alter the local and global topology of DNA so as to promote and counteract the persistent effects of transcription and replication. X-ray crystallography and electron microscopy, coupled with biochemical and single molecule methods are continuing to provide a wealth of mechanistic information on how DNA remodeling factors are employed to dynamically shape and organize the genome.
Collapse
|
33
|
Meinke G, Phelan PJ, Shin J, Gagnon D, Archambault J, Bohm A, Bullock PA. Structural Based Analyses of the JC Virus T-Antigen F258L Mutant Provides Evidence for DNA Dependent Conformational Changes in the C-Termini of Polyomavirus Origin Binding Domains. PLoS Pathog 2016; 12:e1005362. [PMID: 26735515 PMCID: PMC4703215 DOI: 10.1371/journal.ppat.1005362] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 12/04/2015] [Indexed: 11/21/2022] Open
Abstract
The replication of human polyomavirus JCV, which causes Progressive Multifocal Leukoencephalopathy, is initiated by the virally encoded T-antigen (T-ag). The structure of the JC virus T-ag origin-binding domain (OBD) was recently solved by X-ray crystallography. This structure revealed that the OBD contains a C-terminal pocket, and that residues from the multifunctional A1 and B2 motifs situated on a neighboring OBD molecule dock into the pocket. Related studies established that a mutation in a pocket residue (F258L) rendered JCV T-ag unable to support JCV DNA replication. To establish why this mutation inactivated JCV T-ag, we have solved the structure of the F258L JCV T-ag OBD mutant. Based on this structure, it is concluded that the structural consequences of the F258L mutation are limited to the pocket region. Further analyses, utilizing the available polyomavirus OBD structures, indicate that the F258 region is highly dynamic and that the relative positions of F258 are governed by DNA binding. The possible functional consequences of the DNA dependent rearrangements, including promotion of OBD cycling at the replication fork, are discussed.
Collapse
Affiliation(s)
- Gretchen Meinke
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Paul J. Phelan
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Jong Shin
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, New York, United States of America
| | - David Gagnon
- Institut de Recherches Cliniques de Montreal (IRCM), Montreal, Quebec, Canada
- Department of Biochemistry and Molecular Medicine, Universite de Montreal, Montreal, Quebec, Canada
| | - Jacques Archambault
- Institut de Recherches Cliniques de Montreal (IRCM), Montreal, Quebec, Canada
- Department of Biochemistry and Molecular Medicine, Universite de Montreal, Montreal, Quebec, Canada
| | - Andrew Bohm
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Peter A. Bullock
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| |
Collapse
|
34
|
Dewar JM, Budzowska M, Walter JC. The mechanism of DNA replication termination in vertebrates. Nature 2015; 525:345-50. [PMID: 26322582 PMCID: PMC4575634 DOI: 10.1038/nature14887] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 07/01/2015] [Indexed: 12/18/2022]
Abstract
Eukaryotic DNA replication terminates when replisomes from adjacent replication origins converge. Termination involves local completion of DNA synthesis, decatenation of daughter molecules, and replisome disassembly. Termination has been difficult to study because termination events are generally asynchronous and sequence non-specific. To overcome these challenges, we paused converging replisomes with a site-specific barrier in Xenopus egg extracts. Upon removal of the barrier, forks underwent synchronous and site-specific termination, allowing mechanistic dissection of this process. We show that DNA synthesis does not slow detectably as forks approach each other and that leading strands pass each other unhindered before undergoing ligation to downstream lagging strands. Dissociation of CMG helicases occurs only after the final ligation step, and is not required for completion of DNA synthesis, strongly suggesting that converging CMGs pass one another and dissociate from double-stranded DNA. This termination mechanism allows rapid completion of DNA synthesis while avoiding premature replisome disassembly
Collapse
Affiliation(s)
- James M Dewar
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Magda Budzowska
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.,Howard Hughes Medical Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| |
Collapse
|
35
|
Larsen NB, Hickson ID, Mankouri HW. Tus-Ter as a tool to study site-specific DNA replication perturbation in eukaryotes. Cell Cycle 2015; 13:2994-8. [PMID: 25486560 DOI: 10.4161/15384101.2014.958912] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The high-affinity binding of the Tus protein to specific 21-bp sequences, called Ter, causes site-specific, and polar, DNA replication fork arrest in E coli. The Tus-Ter complex serves to coordinate DNA replication with chromosome segregation in this organism. A number of recent and ongoing studies have demonstrated that Tus-Ter can be used as a heterologous tool to generate site-specific perturbation of DNA replication when reconstituted in eukaryotes. Here, we review these recent findings and explore the molecular mechanism by which Tus-Ter mediates replication fork (RF) arrest in the budding yeast, S. cerevisiae. We propose that Tus-Ter is a versatile, genetically tractable, and regulatable RF blocking system that can be utilized for disrupting DNA replication in a diverse range of host cells.
Collapse
Affiliation(s)
- Nicolai B Larsen
- a Center for Healthy Aging; Department of Cellular and Molecular Medicine ; University of Copenhagen ; Copenhagen , Denmark
| | | | | |
Collapse
|
36
|
Chaban Y, Stead JA, Ryzhenkova K, Whelan F, Lamber EP, Antson A, Sanders CM, Orlova EV. Structural basis for DNA strand separation by a hexameric replicative helicase. Nucleic Acids Res 2015; 43:8551-63. [PMID: 26240379 PMCID: PMC4787811 DOI: 10.1093/nar/gkv778] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Accepted: 07/20/2015] [Indexed: 11/12/2022] Open
Abstract
Hexameric helicases are processive DNA unwinding machines but how they engage with a replication fork during unwinding is unknown. Using electron microscopy and single particle analysis we determined structures of the intact hexameric helicase E1 from papillomavirus and two complexes of E1 bound to a DNA replication fork end-labelled with protein tags. By labelling a DNA replication fork with streptavidin (dsDNA end) and Fab (5′ ssDNA) we located the positions of these labels on the helicase surface, showing that at least 10 bp of dsDNA enter the E1 helicase via a side tunnel. In the currently accepted ‘steric exclusion’ model for dsDNA unwinding, the active 3′ ssDNA strand is pulled through a central tunnel of the helicase motor domain as the dsDNA strands are wedged apart outside the protein assembly. Our structural observations together with nuclease footprinting assays indicate otherwise: strand separation is taking place inside E1 in a chamber above the helicase domain and the 5′ passive ssDNA strands exits the assembly through a separate tunnel opposite to the dsDNA entry point. Our data therefore suggest an alternative to the current general model for DNA unwinding by hexameric helicases.
Collapse
Affiliation(s)
- Yuriy Chaban
- Department of Biological Sciences, Birkbeck College, Institute of Structural and Molecular Biology, Malet Street, London WC1E 7HX, UK
| | - Jonathan A Stead
- Academic Unit of Molecular Oncology, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX, UK
| | - Ksenia Ryzhenkova
- Department of Biological Sciences, Birkbeck College, Institute of Structural and Molecular Biology, Malet Street, London WC1E 7HX, UK
| | - Fiona Whelan
- Departament of Biolody, University of York, York YO10 5DD, UK
| | - Ekaterina P Lamber
- Department of Biological Sciences, Birkbeck College, Institute of Structural and Molecular Biology, Malet Street, London WC1E 7HX, UK
| | - Alfred Antson
- Departament of Biolody, University of York, York YO10 5DD, UK
| | - Cyril M Sanders
- Academic Unit of Molecular Oncology, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX, UK
| | - Elena V Orlova
- Department of Biological Sciences, Birkbeck College, Institute of Structural and Molecular Biology, Malet Street, London WC1E 7HX, UK
| |
Collapse
|
37
|
Ishimi Y, Irie D. G364R mutation of MCM4 detected in human skin cancer cells affects DNA helicase activity of MCM4/6/7 complex. J Biochem 2015; 157:561-9. [PMID: 25661590 DOI: 10.1093/jb/mvv015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Accepted: 01/03/2015] [Indexed: 01/08/2023] Open
Abstract
A number of gene mutations are detected in cells derived from human cancer tissues, but roles of these mutations in cancer cell development are largely unknown. We examined G364R mutation of MCM4 detected in human skin cancer cells. Formation of MCM4/6/7 complex is not affected by the mutation. Consistent with this notion, the binding to MCM6 is comparable between the mutant MCM4 and wild-type MCM4. Nuclear localization of this mutant MCM4 expressed in HeLa cells supports this conclusion. Purified MCM4/6/7 complex containing the G364R MCM4 exhibited similar levels of single-stranded DNA binding and ATPase activities to the complex containing wild-type MCM4. However, the mutant complex showed only 30-50% of DNA helicase activity of the wild-type complex. When G364R MCM4 was expressed in HeLa cells, it was fractionated into nuclease-sensitive chromatin fraction, similar to wild-type MCM4. These results suggest that this mutation does not affect assembly of MCM2-7 complex on replication origins but it interferes some step at function of MCM2-7 helicase. Thus, this mutation may contribute to cancer cell development by disturbing DNA replication.
Collapse
Affiliation(s)
- Yukio Ishimi
- College of Science, Ibaraki University, Mito, Ibaraki 351-8511, Japan
| | - Daiki Irie
- College of Science, Ibaraki University, Mito, Ibaraki 351-8511, Japan
| |
Collapse
|
38
|
Dhingra N, Bruck I, Smith S, Ning B, Kaplan DL. Dpb11 protein helps control assembly of the Cdc45·Mcm2-7·GINS replication fork helicase. J Biol Chem 2015; 290:7586-601. [PMID: 25659432 DOI: 10.1074/jbc.m115.640383] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dpb11 is required for the initiation of DNA replication in budding yeast. Dpb11 binds to S-phase cyclin-dependent kinase-phosphorylated Sld2 and Sld3 to form a ternary complex during S phase. The replication fork helicase in eukaryotes is composed of Cdc45, Mcm2-7, and GINS. We show here, using purified proteins from budding yeast, that Dpb11 alone binds to Mcm2-7 and that Dpb11 also competes with GINS for binding to Mcm2-7. Furthermore, Dpb11 binds directly to single-stranded DNA (ssDNA), and ssDNA inhibits the Dpb11 interaction with Mcm2-7. We also found that Dpb11 can recruit Cdc45 to Mcm2-7. We identified a mutant of the BRCT4 motif of Dpb11 that remains bound to Mcm2-7 in the presence of ssDNA (dpb11-m1,m2,m3,m5), and this mutant exhibits a DNA replication defect when expressed in budding yeast cells. Expression of this mutant results in increased interaction between Dpb11 and Mcm2-7 during S phase, impaired GINS interaction with Mcm2-7 during S phase, and decreased replication protein A (RPA) interaction with origin DNA during S phase. We propose a model in which Dpb11 first recruits Cdc45 to Mcm2-7. Dpb11, although bound to Cdc45·Mcm2-7, can block the interaction between GINS and Mcm2-7. Upon extrusion of ssDNA from the central channel of Mcm2-7, Dpb11 dissociates from Mcm2-7, and Dpb11 binds to ssDNA, thereby allowing GINS to bind to Cdc45·Mcm2-7. Finally, we propose that Dpb11 functions with Sld2 and Sld3 to help control the assembly of the replication fork helicase.
Collapse
Affiliation(s)
- Nalini Dhingra
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235 and
| | - Irina Bruck
- the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306-4300
| | - Skye Smith
- the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306-4300
| | - Boting Ning
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235 and
| | - Daniel L Kaplan
- the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306-4300
| |
Collapse
|
39
|
Bruck I, Kaplan DL. The Dbf4-Cdc7 kinase promotes Mcm2-7 ring opening to allow for single-stranded DNA extrusion and helicase assembly. J Biol Chem 2014; 290:1210-21. [PMID: 25471369 DOI: 10.1074/jbc.m114.608232] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The replication fork helicase in eukaryotes is composed of Cdc45, Mcm2-7, and GINS (CMG). The Dbf4-Cdc7 kinase phosphorylates Mcm2 in vitro, but the in vivo role for Dbf4-Cdc7 phosphorylation of Mcm2 is unclear. We find that budding yeast Dbf4-Cdc7 phosphorylates Mcm2 in vivo under normal conditions during S phase. Inhibiting Dbf4-Cdc7 phosphorylation of Mcm2 confers a dominant-negative phenotype with a severe growth defect. Inhibiting Dbf4-Cdc7 phosphorylation of Mcm2 under wild-type expression conditions also results in impaired DNA replication, substantially decreased single-stranded formation at an origin, and markedly disrupted interaction between GINS and Mcm2-7 during S phase. In vitro, Dbf4-Cdc7 kinase (DDK) phosphorylation of Mcm2 substantially weakens the interaction between Mcm2 and Mcm5, and Dbf4-Cdc7 phosphorylation of Mcm2 promotes Mcm2-7 ring opening. The extrusion of ssDNA from the central channel of Mcm2-7 triggers GINS attachment to Mcm2-7. Thus, Dbf4-Cdc7 phosphorylation of Mcm2 may open the Mcm2-7 ring at the Mcm2-Mcm5 interface, allowing for single-stranded DNA extrusion and subsequent GINS assembly with Mcm2-7.
Collapse
Affiliation(s)
- Irina Bruck
- From the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306
| | - Daniel L Kaplan
- From the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306
| |
Collapse
|
40
|
Bochman ML. Roles of DNA helicases in the maintenance of genome integrity. Mol Cell Oncol 2014; 1:e963429. [PMID: 27308340 PMCID: PMC4905024 DOI: 10.4161/23723548.2014.963429] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/25/2014] [Accepted: 09/01/2014] [Indexed: 11/19/2022]
Abstract
Genome integrity is achieved and maintained by the sum of all of the processes in the cell that ensure the faithful duplication and repair of DNA, as well as its genetic transmission from one cell division to the next. As central players in virtually all of the DNA transactions that occur in vivo, DNA helicases (molecular motors that unwind double-stranded DNA to produce single-stranded substrates) represent a crucial enzyme family that is necessary for genomic stability. Indeed, mutations in many human helicase genes are linked to a variety of diseases with symptoms that can be generally described as genomic instability, such as predispositions to cancers. This review focuses on the roles of both DNA replication helicases and recombination/repair helicases in maintaining genome integrity and provides a brief overview of the diseases related to defects in these enzymes.
Collapse
Affiliation(s)
- Matthew L Bochman
- Molecular and Cellular Biochemistry Department; Indiana University ; Bloomington, IN USA
| |
Collapse
|
41
|
Guo W, Wu Z, Song J, Jiang F, Wang Z, Deng S, Walker VK, Zhou S. Juvenile hormone-receptor complex acts on mcm4 and mcm7 to promote polyploidy and vitellogenesis in the migratory locust. PLoS Genet 2014; 10:e1004702. [PMID: 25340846 PMCID: PMC4207617 DOI: 10.1371/journal.pgen.1004702] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 08/23/2014] [Indexed: 11/18/2022] Open
Abstract
Juvenile hormone (JH), a sesquiterpenoid produced by the corpora allata, coordinates insect growth, metamorphosis, and reproduction. While JH action for the repression of larval metamorphosis has been well studied, the molecular basis of JH in promoting adult reproduction has not been fully elucidated. Methoprene-tolerant (Met), the JH receptor, has been recently shown to mediate JH action during metamorphosis as well as in vitellogenesis, but again, the precise mechanism underlying the latter has been lacking. We have now demonstrated using Met RNAi to phenocopy a JH-deprived condition in migratory locusts, that JH stimulates DNA replication and increases ploidy in preparation for vitellogenesis. Mcm4 and Mcm7, two genes in the DNA replication pathway were expressed in the presence of JH and Met. Depletion of Mcm4 or Mcm7 inhibited de novo DNA synthesis and polyploidization, and resulted in the substantial reduction of vitellogenin mRNA levels as well as severely impaired oocyte maturation and ovarian growth. By using luciferase reporter and electrophoretic mobility shift assays, we have shown that Met directly regulates the transcription of Mcm4 and Mcm7 by binding to upstream consensus sequences with E-box or E-box-like motifs. Our work suggests that the JH-receptor complex acts on Mcm4 and Mcm7 to regulate DNA replication and polyploidy for vitellogenesis and oocyte maturation.
Collapse
Affiliation(s)
- Wei Guo
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Zhongxia Wu
- School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Jiasheng Song
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Feng Jiang
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Zhiming Wang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Shun Deng
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | | | - Shutang Zhou
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- * E-mail:
| |
Collapse
|
42
|
The Mcm2-7 replicative helicase: a promising chemotherapeutic target. BIOMED RESEARCH INTERNATIONAL 2014; 2014:549719. [PMID: 25243149 PMCID: PMC4163376 DOI: 10.1155/2014/549719] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 08/08/2014] [Accepted: 08/10/2014] [Indexed: 02/05/2023]
Abstract
Numerous eukaryotic replication factors have served as chemotherapeutic targets. One replication factor that has largely escaped drug development is the Mcm2-7 replicative helicase. This heterohexameric complex forms the licensing system that assembles the replication machinery at origins during initiation, as well as the catalytic core of the CMG (Cdc45-Mcm2-7-GINS) helicase that unwinds DNA during elongation. Emerging evidence suggests that Mcm2-7 is also part of the replication checkpoint, a quality control system that monitors and responds to DNA damage. As the only replication factor required for both licensing and DNA unwinding, Mcm2-7 is a major cellular regulatory target with likely cancer relevance. Mutations in at least one of the six MCM genes are particularly prevalent in squamous cell carcinomas of the lung, head and neck, and prostrate, and MCM mutations have been shown to cause cancer in mouse models. Moreover various cellular regulatory proteins, including the Rb tumor suppressor family members, bind Mcm2-7 and inhibit its activity. As a preliminary step toward drug development, several small molecule inhibitors that target Mcm2-7 have been recently discovered. Both its structural complexity and essential role at the interface between DNA replication and its regulation make Mcm2-7 a potential chemotherapeutic target.
Collapse
|
43
|
Larsen NB, Sass E, Suski C, Mankouri HW, Hickson ID. The Escherichia coli Tus-Ter replication fork barrier causes site-specific DNA replication perturbation in yeast. Nat Commun 2014; 5:3574. [PMID: 24705096 DOI: 10.1038/ncomms4574] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 03/06/2014] [Indexed: 01/01/2023] Open
Abstract
Replication fork (RF) pausing occurs at both 'programmed' sites and non-physiological barriers (for example, DNA adducts). Programmed RF pausing is required for site-specific DNA replication termination in Escherichia coli, and this process requires the binding of the polar terminator protein, Tus, to specific DNA sequences called Ter. Here, we demonstrate that Tus-Ter modules also induce polar RF pausing when engineered into the Saccharomyces cerevisiae genome. This heterologous RF barrier is distinct from a number of previously characterized, protein-mediated, RF pause sites in yeast, as it is neither Tof1-dependent nor counteracted by the Rrm3 helicase. Although the yeast replisome can overcome RF pausing at Tus-Ter modules, this event triggers site-specific homologous recombination that requires the RecQ helicase, Sgs1, for its timely resolution. We propose that Tus-Ter can be utilized as a versatile, site-specific, heterologous DNA replication-perturbing system, with a variety of potential applications.
Collapse
Affiliation(s)
- Nicolai B Larsen
- Nordea Center for Healthy Aging, Department of Cellular and Molecular Medicine, Panum Institute 18.1, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Ehud Sass
- 1] Nordea Center for Healthy Aging, Department of Cellular and Molecular Medicine, Panum Institute 18.1, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark [2] Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK [3]
| | - Catherine Suski
- 1] Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK [2]
| | - Hocine W Mankouri
- 1] Nordea Center for Healthy Aging, Department of Cellular and Molecular Medicine, Panum Institute 18.1, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark [2] Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Ian D Hickson
- 1] Nordea Center for Healthy Aging, Department of Cellular and Molecular Medicine, Panum Institute 18.1, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark [2] Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| |
Collapse
|
44
|
Froelich CA, Kang S, Epling LB, Bell SP, Enemark EJ. A conserved MCM single-stranded DNA binding element is essential for replication initiation. eLife 2014; 3:e01993. [PMID: 24692448 PMCID: PMC3970758 DOI: 10.7554/elife.01993] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The ring-shaped MCM helicase is essential to all phases of DNA replication. The complex loads at replication origins as an inactive double-hexamer encircling duplex DNA. Helicase activation converts this species to two active single hexamers that encircle single-stranded DNA (ssDNA). The molecular details of MCM DNA interactions during these events are unknown. We determined the crystal structure of the Pyrococcus furiosus MCM N-terminal domain hexamer bound to ssDNA and define a conserved MCM-ssDNA binding motif (MSSB). Intriguingly, ssDNA binds the MCM ring interior perpendicular to the central channel with defined polarity. In eukaryotes, the MSSB is conserved in several Mcm2-7 subunits, and MSSB mutant combinations in S. cerevisiae Mcm2-7 are not viable. Mutant Mcm2-7 complexes assemble and are recruited to replication origins, but are defective in helicase loading and activation. Our findings identify an important MCM-ssDNA interaction and suggest it functions during helicase activation to select the strand for translocation. DOI:http://dx.doi.org/10.7554/eLife.01993.001 When DNA was first recognised to be a double helix, it was clear that this structure could easily explain how DNA could be replicated. Each strand was made of bases—represented by the letters ‘A’, ‘C’, ‘G’ and ‘T’—and the two strands were held together by bonds between pairs of bases, one from each strand. Moreover, ‘A’ always paired with ‘T’, and ‘C’ always paired with ‘G’. Therefore, if the two strands were separated, each could be used as a template to guide the synthesis of a new complementary strand and thus create two copies of the original double-stranded molecule. One of the first steps in this replication process involves a ring-shaped complex of six proteins, called an MCM helicase, separating the two strands. To prepare for DNA replication, two MCM helicase rings wrap around the double-stranded DNA. Then, after the helicase has been activated, the bonds between the DNA base pairs break, and the two rings separate with one ring encircling each DNA strand. However, the details of the interactions between the helicase and the DNA during these events are not fully understood. Now Froelich, Kang et al. have solved the three-dimensional structure of an MCM helicase ring—taken from a microbe originally found at deep ocean vents—on its own and also when bound to a short piece of single-stranded DNA. The helicase ring becomes more oval when the DNA binds to it. Moreover, rather than passing straight through the ring, the DNA wraps part of the way around the inside of the ring. Specific amino acids—the building blocks of proteins—on the inside of the ring interact with the single-stranded DNA, and these amino acids are also found in MCM proteins in many other organisms. Furthermore, swapping these amino acids for different amino acids significantly reduced the ability of the ring to bind to single-stranded DNA, but its ability to bind to double-stranded DNA was only slightly affected. Engineering similar changes into the ring complexes of yeast cells was lethal, and the mutant complexes were less able to be loaded onto the DNA, or to be activated and separate the two strands ready for replication. These insights into how helicases are loaded onto double-stranded DNA, and select one DNA strand to encircle, have improved our understanding of how DNA replication is initiated: a process that is vital for living things. DOI:http://dx.doi.org/10.7554/eLife.01993.002
Collapse
Affiliation(s)
- Clifford A Froelich
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, United States
| | | | | | | | | |
Collapse
|
45
|
Lam SKW, Ma X, Sing TL, Shilton BH, Brandl CJ, Davey MJ. The PS1 hairpin of Mcm3 is essential for viability and for DNA unwinding in vitro. PLoS One 2013; 8:e82177. [PMID: 24349215 PMCID: PMC3859580 DOI: 10.1371/journal.pone.0082177] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 10/21/2013] [Indexed: 11/19/2022] Open
Abstract
The pre-sensor 1 (PS1) hairpin is found in ring-shaped helicases of the AAA+ family (ATPases associated with a variety of cellular activities) of proteins and is implicated in DNA translocation during DNA unwinding of archaeal mini-chromosome maintenance (MCM) and superfamily 3 viral replicative helicases. To determine whether the PS1 hairpin is required for the function of the eukaryotic replicative helicase, Mcm2-7 (also comprised of AAA+ proteins), we mutated the conserved lysine residue in the putative PS1 hairpin motif in each of the Saccharomyces cerevisiae Mcm2-7 subunits to alanine. Interestingly, only the PS1 hairpin of Mcm3 was essential for viability. While mutation of the PS1 hairpin in the remaining MCM subunits resulted in minimal phenotypes, with the exception of Mcm7 which showed slow growth under all conditions examined, the viable alleles were synthetic lethal with each other. Reconstituted Mcm2-7 containing Mcm3 with the PS1 mutation (Mcm3(K499A)) had severely decreased helicase activity. The lack of helicase activity provides a probable explanation for the inviability of the mcm3(K499A) strain. The ATPase activity of Mcm2-7(3K499A) was similar to the wild type complex, but its interaction with single-stranded DNA in an electrophoretic mobility shift assay and its associations in cells were subtly altered. Together, these findings indicate that the PS1 hairpins in the Mcm2-7 subunits have important and distinct functions, most evident by the essential nature of the Mcm3 PS1 hairpin in DNA unwinding.
Collapse
Affiliation(s)
- Simon K. W. Lam
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Xiaoli Ma
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Tina L. Sing
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Brian H. Shilton
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Christopher J. Brandl
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
- * E-mail:
| | - Megan J. Davey
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| |
Collapse
|
46
|
Ribeck N, Saleh OA. DNA unwinding by ring-shaped T4 helicase gp41 is hindered by tension on the occluded strand. PLoS One 2013; 8:e79237. [PMID: 24250825 PMCID: PMC3826741 DOI: 10.1371/journal.pone.0079237] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 09/20/2013] [Indexed: 01/12/2023] Open
Abstract
The replicative helicase for bacteriophage T4 is gp41, which is a ring-shaped hexameric motor protein that achieves unwinding of dsDNA by translocating along one strand of ssDNA while forcing the opposite strand to the outside of the ring. While much study has been dedicated to the mechanism of binding and translocation along the ssDNA strand encircled by ring-shaped helicases, relatively little is known about the nature of the interaction with the opposite, ‘occluded’ strand. Here, we investigate the interplay between the bacteriophage T4 helicase gp41 and the ss/dsDNA fork by measuring, at the single-molecule level, DNA unwinding events on stretched DNA tethers in multiple geometries. We find that gp41 activity is significantly dependent on the geometry and tension of the occluded strand, suggesting an interaction between gp41 and the occluded strand that stimulates the helicase. However, the geometry dependence of gp41 activity is the opposite of that found previously for the E. coli hexameric helicase DnaB. Namely, tension applied between the occluded strand and dsDNA stem inhibits unwinding activity by gp41, while tension pulling apart the two ssDNA tails does not hinder its activity. This implies a distinct variation in helicase-occluded strand interactions among superfamily IV helicases, and we propose a speculative model for this interaction that is consistent with both the data presented here on gp41 and the data that had been previously reported for DnaB.
Collapse
Affiliation(s)
- Noah Ribeck
- Department of Physics, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Omar A. Saleh
- Department of Materials and Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, California, United States of America
- * E-mail:
| |
Collapse
|
47
|
You Z, De Falco M, Kamada K, Pisani FM, Masai H. The mini-chromosome maintenance (Mcm) complexes interact with DNA polymerase α-primase and stimulate its ability to synthesize RNA primers. PLoS One 2013; 8:e72408. [PMID: 23977294 PMCID: PMC3748026 DOI: 10.1371/journal.pone.0072408] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 07/16/2013] [Indexed: 01/14/2023] Open
Abstract
The Mini-chromosome maintenance (Mcm) proteins are essential as central components for the DNA unwinding machinery during eukaryotic DNA replication. DNA primase activity is required at the DNA replication fork to synthesize short RNA primers for DNA chain elongation on the lagging strand. Although direct physical and functional interactions between helicase and primase have been known in many prokaryotic and viral systems, potential interactions between helicase and primase have not been explored in eukaryotes. Using purified Mcm and DNA primase complexes, a direct physical interaction is detected in pull-down assays between the Mcm2∼7 complex and the hetero-dimeric DNA primase composed of the p48 and p58 subunits. The Mcm4/6/7 complex co-sediments with the primase and the DNA polymerase α-primase complex in glycerol gradient centrifugation and forms a Mcm4/6/7-primase-DNA ternary complex in gel-shift assays. Both the Mcm4/6/7 and Mcm2∼7 complexes stimulate RNA primer synthesis by DNA primase in vitro. However, primase inhibits the Mcm4/6/7 helicase activity and this inhibition is abolished by the addition of competitor DNA. In contrast, the ATP hydrolysis activity of Mcm4/6/7 complex is not affected by primase. Mcm and primase proteins mutually stimulate their DNA-binding activities. Our findings indicate that a direct physical interaction between primase and Mcm proteins may facilitate priming reaction by the former protein, suggesting that efficient DNA synthesis through helicase-primase interactions may be conserved in eukaryotic chromosomes.
Collapse
Affiliation(s)
- Zhiying You
- Genome Dynamics Project, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
| | | | | | | | | |
Collapse
|
48
|
Bell SP, Kaguni JM. Helicase loading at chromosomal origins of replication. Cold Spring Harb Perspect Biol 2013; 5:cshperspect.a010124. [PMID: 23613349 DOI: 10.1101/cshperspect.a010124] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Loading of the replicative DNA helicase at origins of replication is of central importance in DNA replication. As the first of the replication fork proteins assemble at chromosomal origins of replication, the loaded helicase is required for the recruitment of the rest of the replication machinery. In this work, we review the current knowledge of helicase loading at Escherichia coli and eukaryotic origins of replication. In each case, this process requires both an origin recognition protein as well as one or more additional proteins. Comparison of these events shows intriguing similarities that suggest a similar underlying mechanism, as well as critical differences that likely reflect the distinct processes that regulate helicase loading in bacterial and eukaryotic cells.
Collapse
Affiliation(s)
- Stephen P Bell
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | |
Collapse
|
49
|
Jeong YJ, Rajagopal V, Patel SS. Switching from single-stranded to double-stranded DNA limits the unwinding processivity of ring-shaped T7 DNA helicase. Nucleic Acids Res 2013; 41:4219-29. [PMID: 23446275 PMCID: PMC3627605 DOI: 10.1093/nar/gkt133] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Phage T7 helicase unwinds double-stranded DNA (dsDNA) by encircling one strand while excluding the complementary strand from its central channel. When T7 helicase translocates on single-stranded DNA (ssDNA), it has kilobase processivity; yet, it is unable to processively unwind linear dsDNA, even 60 base-pairs long. Particularly, the GC-rich dsDNAs are unwound with lower amplitudes under single-turnover conditions. Here, we provide evidence that T7 helicase switches from ssDNA to dsDNA during DNA unwinding. The switching propensity is higher when dsDNA is GC-rich or when the 3′-overhang of forked DNA is <15 bases. Once helicase encircles dsDNA, it travels along dsDNA and dissociates from the end of linear DNA without strand separation, which explains the low unwinding amplitude of these substrates. Trapping the displaced strand with ssDNA binding protein or changing its composition to morpholino oligomer that does not interact with helicase increases the unwinding amplitude. We conclude that the displaced strand must be continuously excluded and kept away from the central channel for processive DNA unwinding. The finding that T7 helicase can switch from ssDNA to dsDNA binding mode during unwinding provides new insights into ways of limiting DNA unwinding and triggering fork regression when stalled forks need to be restarted.
Collapse
Affiliation(s)
- Yong-Joo Jeong
- Department of Biochemistry, UMDNJ-Robert Wood Johnson Medical School 675 Hoes Lane, Piscataway, NJ 08854, USA
| | | | | |
Collapse
|
50
|
Bruck I, Kaplan DL. Cdc45 protein-single-stranded DNA interaction is important for stalling the helicase during replication stress. J Biol Chem 2013; 288:7550-7563. [PMID: 23382391 DOI: 10.1074/jbc.m112.440941] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Replicative polymerase stalling is coordinated with replicative helicase stalling in eukaryotes, but the mechanism underlying this coordination is not known. Cdc45 activates the Mcm2-7 helicase. We report here that Cdc45 from budding yeast binds tightly to long (≥ 40 nucleotides) genomic single-stranded DNA (ssDNA) and that 60mer ssDNA specifically disrupts the interaction between Cdc45 and Mcm2-7. We identified a mutant of Cdc45 that does not bind to ssDNA. When this mutant of cdc45 is expressed in budding yeast cells exposed to hydroxyurea, cell growth is severely inhibited, and excess RPA accumulates at or near an origin. Chromatin immunoprecipitation suggests that helicase movement is uncoupled from polymerase movement for mutant cells exposed to hydroxyurea. These data suggest that Cdc45-ssDNA interaction is important for stalling the helicase during replication stress.
Collapse
Affiliation(s)
- Irina Bruck
- Florida State University College of Medicine, Department of Biomedical Sciences, Tallahassee, Florida 32306
| | - Daniel L Kaplan
- Florida State University College of Medicine, Department of Biomedical Sciences, Tallahassee, Florida 32306.
| |
Collapse
|