1
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Mullins EA, Salay LE, Durie CL, Bradley NP, Jackman JE, Ohi MD, Chazin WJ, Eichman BF. A mechanistic model of primer synthesis from catalytic structures of DNA polymerase α-primase. Nat Struct Mol Biol 2024; 31:777-790. [PMID: 38491139 PMCID: PMC11102853 DOI: 10.1038/s41594-024-01227-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Accepted: 01/12/2024] [Indexed: 03/18/2024]
Abstract
The mechanism by which polymerase α-primase (polα-primase) synthesizes chimeric RNA-DNA primers of defined length and composition, necessary for replication fidelity and genome stability, is unknown. Here, we report cryo-EM structures of Xenopus laevis polα-primase in complex with primed templates representing various stages of DNA synthesis. Our data show how interaction of the primase regulatory subunit with the primer 5' end facilitates handoff of the primer to polα and increases polα processivity, thereby regulating both RNA and DNA composition. The structures detail how flexibility within the heterotetramer enables synthesis across two active sites and provide evidence that termination of DNA synthesis is facilitated by reduction of polα and primase affinities for the varied conformations along the chimeric primer-template duplex. Together, these findings elucidate a critical catalytic step in replication initiation and provide a comprehensive model for primer synthesis by polα-primase.
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Affiliation(s)
- Elwood A Mullins
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
| | - Lauren E Salay
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Clarissa L Durie
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Biochemistry, University of Missouri, Columbia, MO, USA
| | - Noah P Bradley
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
| | - Jane E Jackman
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Melanie D Ohi
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Walter J Chazin
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA.
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA.
- Department of Chemistry, Vanderbilt University, Nashville, TN, USA.
| | - Brandt F Eichman
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA.
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA.
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA.
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2
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Baranovskiy AG, Morstadt LM, Babayeva ND, Tahirov TH. Human primosome requires replication protein A when copying DNA with inverted repeats. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.11.584335. [PMID: 38559116 PMCID: PMC10979909 DOI: 10.1101/2024.03.11.584335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The human primosome, a four-subunit complex of primase and DNA polymerase alpha (Polα), initiates DNA synthesis on both chromosome strands by generating chimeric RNA-DNA primers for loading DNA polymerases delta and epsilon (Polε). Replication protein A (RPA) tightly binds to single-stranded DNA strands, protecting them from nucleolytic digestion and unauthorized transactions. We report here that RPA plays a critical role for the human primosome during DNA synthesis across inverted repeats prone to hairpin formation. On other alternatively structured DNA forming a G-quadruplex, RPA provides no assistance for primosome. A stimulatory effect of RPA on DNA synthesis across hairpins was also observed for the catalytic domain of Polα but not of Polε. The important factors for an efficient hairpin bypass by primosome are the high affinity of RPA to DNA based on four DNA-binding domains and the interaction of the winged-helix-turn-helix domain of RPA with Polα. Binding studies indicate that this interaction stabilizes the RPA/Polα complex on the primed template. This work provides insight into a cooperative action of RPA and primosome on DNA, which is critical for DNA synthesis across inverted repeats.
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3
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Nasheuer HP, Meaney AM, Hulshoff T, Thiele I, Onwubiko NO. Replication Protein A, the Main Eukaryotic Single-Stranded DNA Binding Protein, a Focal Point in Cellular DNA Metabolism. Int J Mol Sci 2024; 25:588. [PMID: 38203759 PMCID: PMC10779431 DOI: 10.3390/ijms25010588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 12/28/2023] [Accepted: 12/29/2023] [Indexed: 01/12/2024] Open
Abstract
Replication protein A (RPA) is a heterotrimeric protein complex and the main single-stranded DNA (ssDNA)-binding protein in eukaryotes. RPA has key functions in most of the DNA-associated metabolic pathways and DNA damage signalling. Its high affinity for ssDNA helps to stabilise ssDNA structures and protect the DNA sequence from nuclease attacks. RPA consists of multiple DNA-binding domains which are oligonucleotide/oligosaccharide-binding (OB)-folds that are responsible for DNA binding and interactions with proteins. These RPA-ssDNA and RPA-protein interactions are crucial for DNA replication, DNA repair, DNA damage signalling, and the conservation of the genetic information of cells. Proteins such as ATR use RPA to locate to regions of DNA damage for DNA damage signalling. The recruitment of nucleases and DNA exchange factors to sites of double-strand breaks are also an important RPA function to ensure effective DNA recombination to correct these DNA lesions. Due to its high affinity to ssDNA, RPA's removal from ssDNA is of central importance to allow these metabolic pathways to proceed, and processes to exchange RPA against downstream factors are established in all eukaryotes. These faceted and multi-layered functions of RPA as well as its role in a variety of human diseases will be discussed.
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Affiliation(s)
- Heinz Peter Nasheuer
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, Biochemistry, University of Galway, H91 TK33 Galway, Ireland
| | - Anna Marie Meaney
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, Biochemistry, University of Galway, H91 TK33 Galway, Ireland
| | - Timothy Hulshoff
- Molecular Systems Physiology Group, School of Biological and Chemical Sciences, University of Galway, H91 TK33 Galway, Ireland
| | - Ines Thiele
- Molecular Systems Physiology Group, School of Biological and Chemical Sciences, University of Galway, H91 TK33 Galway, Ireland
| | - Nichodemus O. Onwubiko
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, Biochemistry, University of Galway, H91 TK33 Galway, Ireland
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4
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Cordoba JJ, Mullins EA, Salay LE, Eichman BF, Chazin WJ. Flexibility and Distributive Synthesis Regulate RNA Priming and Handoff in Human DNA Polymerase α-Primase. J Mol Biol 2023; 435:168330. [PMID: 37884206 PMCID: PMC10872500 DOI: 10.1016/j.jmb.2023.168330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/22/2023] [Accepted: 10/18/2023] [Indexed: 10/28/2023]
Abstract
DNA replication in eukaryotes relies on the synthesis of a ∼30-nucleotide RNA/DNA primer strand through the dual action of the heterotetrameric polymerase α-primase (pol-prim) enzyme. Synthesis of the 7-10-nucleotide RNA primer is regulated by the C-terminal domain of the primase regulatory subunit (PRIM2C) and is followed by intramolecular handoff of the primer to pol α for extension by ∼20 nucleotides of DNA. Here, we provide evidence that RNA primer synthesis is governed by a combination of the high affinity and flexible linkage of the PRIM2C domain and the surprisingly low affinity of the primase catalytic domain (PRIM1) for substrate. Using a combination of small angle X-ray scattering and electron microscopy, we found significant variability in the organization of PRIM2C and PRIM1 in the absence and presence of substrate, and that the population of structures with both PRIM2C and PRIM1 in a configuration aligned for synthesis is low. Crosslinking was used to visualize the orientation of PRIM2C and PRIM1 when engaged by substrate as observed by electron microscopy. Microscale thermophoresis was used to measure substrate affinities for a series of pol-prim constructs, which showed that the PRIM1 catalytic domain does not bind the template or emergent RNA-primed templates with appreciable affinity. Together, these findings support a model of RNA primer synthesis in which generation of the nascent RNA strand and handoff of the RNA-primed template from primase to polymerase α is mediated by the high degree of inter-domain flexibility of pol-prim, the ready dissociation of PRIM1 from its substrate, and the much higher affinity of the POLA1cat domain of polymerase α for full-length RNA-primed templates.
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Affiliation(s)
- John J Cordoba
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
| | - Elwood A Mullins
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA; Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Lauren E Salay
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN, USA; Department of Biochemistry, Vanderbilt University, Nashville, TN, USA
| | - Brandt F Eichman
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN, USA; Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA; Department of Biochemistry, Vanderbilt University, Nashville, TN, USA
| | - Walter J Chazin
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN, USA; Department of Biochemistry, Vanderbilt University, Nashville, TN, USA; Department of Chemistry, Vanderbilt University, Nashville, TN, USA.
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5
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He Q, Lim CJ. Models for human telomere C-strand fill-in by CST-Polα-primase. Trends Biochem Sci 2023; 48:860-872. [PMID: 37586999 PMCID: PMC10528720 DOI: 10.1016/j.tibs.2023.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 07/12/2023] [Accepted: 07/18/2023] [Indexed: 08/18/2023]
Abstract
Telomere maintenance is essential for the genome integrity of eukaryotes, and this function is underpinned by the two-step telomeric DNA synthesis process: telomere G-overhang extension by telomerase and complementary strand fill-in by DNA polymerase alpha-primase (polα-primase). Compared to the telomerase step, the telomere C-strand fill-in mechanism is less understood. Recent studies have provided new insights into how telomeric single-stranded DNA-binding protein CTC1-STN1-TEN1 (CST) and polα-primase coordinate to synthesize the telomeric C-strand for telomere overhang fill-in. Cryogenic electron microscopy (cryo-EM) structures of CST-polα-primase complexes have provided additional insights into how they assemble at telomeric templates and de novo synthesize the telomere C-strand. In this review, we discuss how these latest findings coalesce with existing understanding to develop a human telomere C-strand fill-in mechanism model.
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Affiliation(s)
- Qixiang He
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Ci Ji Lim
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA.
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6
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Mullins EA, Salay LE, Durie CL, Bradley NP, Jackman JE, Ohi MD, Chazin WJ, Eichman BF. A mechanistic model of primer synthesis from catalytic structures of DNA polymerase α-primase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.16.533013. [PMID: 36993335 PMCID: PMC10055150 DOI: 10.1101/2023.03.16.533013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The mechanism by which polymerase α-primase (polα-primase) synthesizes chimeric RNA-DNA primers of defined length and composition, necessary for replication fidelity and genome stability, is unknown. Here, we report cryo-EM structures of polα-primase in complex with primed templates representing various stages of DNA synthesis. Our data show how interaction of the primase regulatory subunit with the primer 5'-end facilitates handoff of the primer to polα and increases polα processivity, thereby regulating both RNA and DNA composition. The structures detail how flexibility within the heterotetramer enables synthesis across two active sites and provide evidence that termination of DNA synthesis is facilitated by reduction of polα and primase affinities for the varied conformations along the chimeric primer/template duplex. Together, these findings elucidate a critical catalytic step in replication initiation and provide a comprehensive model for primer synthesis by polα-primase.
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7
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Jones ML, Aria V, Baris Y, Yeeles JTP. How Pol α-primase is targeted to replisomes to prime eukaryotic DNA replication. Mol Cell 2023; 83:2911-2924.e16. [PMID: 37506699 PMCID: PMC10501992 DOI: 10.1016/j.molcel.2023.06.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 06/16/2023] [Accepted: 06/28/2023] [Indexed: 07/30/2023]
Abstract
During eukaryotic DNA replication, Pol α-primase generates primers at replication origins to start leading-strand synthesis and every few hundred nucleotides during discontinuous lagging-strand replication. How Pol α-primase is targeted to replication forks to prime DNA synthesis is not fully understood. Here, by determining cryoelectron microscopy (cryo-EM) structures of budding yeast and human replisomes containing Pol α-primase, we reveal a conserved mechanism for the coordination of priming by the replisome. Pol α-primase binds directly to the leading edge of the CMG (CDC45-MCM-GINS) replicative helicase via a complex interaction network. The non-catalytic PRIM2/Pri2 subunit forms two interfaces with CMG that are critical for in vitro DNA replication and yeast cell growth. These interactions position the primase catalytic subunit PRIM1/Pri1 directly above the exit channel for lagging-strand template single-stranded DNA (ssDNA), revealing why priming occurs efficiently only on the lagging-strand template and elucidating a mechanism for Pol α-primase to overcome competition from RPA to initiate primer synthesis.
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Affiliation(s)
- Morgan L Jones
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Valentina Aria
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Yasemin Baris
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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8
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Boldinova EO, Baranovskiy AG, Gagarinskaya DI, Manukyan A, Makarova A, Tahirov T. The role of catalytic and regulatory domains of human PrimPol in DNA binding and synthesis. Nucleic Acids Res 2023; 51:7541-7551. [PMID: 37326028 PMCID: PMC10415149 DOI: 10.1093/nar/gkad507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 04/28/2023] [Accepted: 05/31/2023] [Indexed: 06/17/2023] Open
Abstract
Human PrimPol possesses DNA primase and DNA polymerase activities and restarts stalled replication forks protecting cells against DNA damage in nuclei and mitochondria. The zinc-binding motif (ZnFn) of the C-terminal domain (CTD) of PrimPol is required for DNA primase activity but the mechanism is not clear. In this work, we biochemically demonstrate that PrimPol initiates de novo DNA synthesis in cis-orientation, when the N-terminal catalytic domain (NTD) and the CTD of the same molecule cooperate for substrates binding and catalysis. The modeling studies revealed that PrimPol uses a similar mode of initiating NTP coordination as the human primase. The ZnFn motif residue Arg417 is required for binding the 5'-triphosphate group that stabilizes the PrimPol complex with a DNA template-primer. We found that the NTD alone is able to initiate DNA synthesis, and the CTD stimulates the primase activity of NTD. The regulatory role of the RPA-binding motif in the modulation of PrimPol binding to DNA is also demonstrated.
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Affiliation(s)
- Elizaveta O Boldinova
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Kurchatov sq. 2, 123182 Moscow, Russia
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov 34/5, 119334 Moscow, Russia
| | - Andrey G Baranovskiy
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Diana I Gagarinskaya
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Kurchatov sq. 2, 123182 Moscow, Russia
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Anna A Manukyan
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Kurchatov sq. 2, 123182 Moscow, Russia
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov 34/5, 119334 Moscow, Russia
| | - Alena V Makarova
- Institute of Molecular Genetics, National Research Center "Kurchatov Institute", Kurchatov sq. 2, 123182 Moscow, Russia
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov 34/5, 119334 Moscow, Russia
| | - Tahir H Tahirov
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
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9
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Cordoba JJ, Mullins EA, Salay LE, Eichman BF, Chazin WJ. Flexibility and distributive synthesis regulate RNA priming and handoff in human DNA polymerase α-primase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.01.551538. [PMID: 37577606 PMCID: PMC10418221 DOI: 10.1101/2023.08.01.551538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
DNA replication in eukaryotes relies on the synthesis of a ~30-nucleotide RNA/DNA primer strand through the dual action of the heterotetrameric polymerase α-primase (pol-prim) enzyme. Synthesis of the 7-10-nucleotide RNA primer is regulated by the C-terminal domain of the primase regulatory subunit (PRIM2C) and is followed by intramolecular handoff of the primer to pol α for extension by ~20 nucleotides of DNA. Here we provide evidence that RNA primer synthesis is governed by a combination of the high affinity and flexible linkage of the PRIM2C domain and the low affinity of the primase catalytic domain (PRIM1) for substrate. Using a combination of small angle X-ray scattering and electron microscopy, we found significant variability in the organization of PRIM2C and PRIM1 in the absence and presence of substrate, and that the population of structures with both PRIM2C and PRIM1 in a configuration aligned for synthesis is low. Crosslinking was used to visualize the orientation of PRIM2C and PRIM1 when engaged by substrate as observed by electron microscopy. Microscale thermophoresis was used to measure substrate affinities for a series of pol-prim constructs, which showed that the PRIM1 catalytic domain does not bind the template or emergent RNA-primed templates with appreciable affinity. Together, these findings support a model of RNA primer synthesis in which generation of the nascent RNA strand and handoff of the RNA-primed template from primase to polymerase α is mediated by the high degree of inter-domain flexibility of pol-prim, the ready dissociation of PRIM1 from its substrate, and the much higher affinity of the POLA1cat domain of polymerase α for full-length RNA-primed templates.
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Affiliation(s)
- John J. Cordoba
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee, USA
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Elwood A. Mullins
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Lauren E. Salay
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee, USA
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Brandt F. Eichman
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee, USA
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Walter J. Chazin
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee, USA
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
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10
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Yuan Z, Georgescu R, Li H, O'Donnell ME. Molecular choreography of primer synthesis by the eukaryotic Pol α-primase. Nat Commun 2023; 14:3697. [PMID: 37344454 PMCID: PMC10284912 DOI: 10.1038/s41467-023-39441-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 06/14/2023] [Indexed: 06/23/2023] Open
Abstract
The eukaryotic polymerase α (Pol α) synthesizes an RNA-DNA hybrid primer of 20-30 nucleotides. Pol α is composed of Pol1, Pol12, Primase 1 (Pri1), and Pri2. Pol1 and Pri1 contain the DNA polymerase and RNA primase activities, respectively. It has been unclear how Pol α hands over an RNA primer from Pri1 to Pol1 for DNA primer extension, and how the primer length is defined. Here we report the cryo-EM analysis of yeast Pol α in the apo, primer initiation, primer elongation, RNA primer hand-off from Pri1 to Pol1, and DNA extension states, revealing a series of very large movements. We reveal a critical point at which Pol1-core moves to take over the 3'-end of the RNA from Pri1. DNA extension is limited by a spiral motion of Pol1-core. Since both Pri1 and Pol1-core are flexibly attached to a stable platform, primer growth produces stress that limits the primer length.
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Affiliation(s)
- Zuanning Yuan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Roxana Georgescu
- DNA Replication Laboratory and Howard Hughes Medical Institute, Rockefeller University, New York, NY, USA
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA.
| | - Michael E O'Donnell
- DNA Replication Laboratory and Howard Hughes Medical Institute, Rockefeller University, New York, NY, USA.
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11
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Schneider A, Bergsch J, Lipps G. The monomeric archaeal primase from Nanoarchaeum equitans harbours the features of heterodimeric archaeoeukaryotic primases and primes sequence-specifically. Nucleic Acids Res 2023; 51:5087-5105. [PMID: 37099378 PMCID: PMC10250227 DOI: 10.1093/nar/gkad261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 03/17/2023] [Accepted: 03/29/2023] [Indexed: 04/27/2023] Open
Abstract
The marine thermophilic archaeon Nanoarchaeum equitans possesses a monomeric primase encompassing the conserved domains of the small catalytic and the large regulatory subunits of archaeoeukaryotic heterodimeric primases in one protein chain. The recombinant protein primes on templates containing a triplet with a central thymidine, thus displaying a pronounced sequence specificity typically observed with bacterial type primases only. The N. equitans primase (NEQ395) is a highly active primase enzyme synthesizing short RNA primers. Termination occurs preferentially at about nine nucleotides, as determined by HPLC analysis and confirmed with mass spectrometry. Possibly, the compact monomeric primase NEQ395 represents the minimal archaeoeukaryotic primase and could serve as a functional and structural model of the heterodimeric archaeoeukaryotic primases, whose study is hindered by engagement in protein assemblies and rather low activity.
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Affiliation(s)
- Andy Schneider
- Institute of Chemistry and Bioanalytics, University of Applied Sciences Northwestern Switzerland, 4132 Muttenz, Switzerland
| | - Jan Bergsch
- Institute of Chemistry and Bioanalytics, University of Applied Sciences Northwestern Switzerland, 4132 Muttenz, Switzerland
| | - Georg Lipps
- Institute of Chemistry and Bioanalytics, University of Applied Sciences Northwestern Switzerland, 4132 Muttenz, Switzerland
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12
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Yuan Z, Georgescu R, Li H, O'Donnell ME. Molecular choreography of primer synthesis by the eukaryotic Pol α-primase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.03.539257. [PMID: 37205351 PMCID: PMC10187153 DOI: 10.1101/2023.05.03.539257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The eukaryotic polymerase α (Pol α) is a dual-function DNA polymerase/primase complex that synthesizes an RNA-DNA hybrid primer of 20-30 nucleotides for DNA replication. Pol α is composed of Pol1, Pol12, Primase 1 (Pri1), and Pri2, with Pol1 and Pri1 containing the DNA polymerase activity and RNA primase activity, respectively, whereas Pol12 and Pri2 serve a structural role. It has been unclear how Pol α hands over an RNA primer made by Pri1 to Pol1 for DNA primer extension, and how the primer length is defined, perhaps due to the difficulty in studying the highly mobile structure. Here we report a comprehensive cryo-EM analysis of the intact 4-subunit yeast Pol α in the apo, primer initiation, primer elongation, RNA primer hand-off from Pri1 to Pol1, and DNA extension states in a 3.5 Å - 5.6 Å resolution range. We found that Pol α is a three-lobed flexible structure. Pri2 functions as a flexible hinge that holds together the catalytic Pol1-core, and the noncatalytic Pol1 CTD that binds to Pol 12 to form a stable platform upon which the other components are organized. In the apo state, Pol1-core is sequestered on the Pol12-Pol1-CTD platform, and Pri1 is mobile perhaps in search of a template. Upon binding a ssDNA template, a large conformation change is induced that enables Pri1 to perform RNA synthesis, and positions Pol1-core to accept the future RNA primed site 50 Å upstream of where Pri1 binds. We reveal in detail the critical point at which Pol1-core takes over the 3'-end of the RNA from Pri1. DNA primer extension appears limited by the spiral motion of Pol1-core while Pri2-CTD stably holds onto the 5' end of the RNA primer. Since both Pri1 and Pol1-core are attached via two linkers to the platform, primer growth will produce stress within this "two-point" attachment that may limit the length of the RNA-DNA hybrid primer. Hence, this study reveals the large and dynamic series of movements that Pol α undergoes to synthesize a primer for DNA replication.
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13
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Human primase hangs on the primer-template and Polα to facilitate primer termination. Nat Struct Mol Biol 2023; 30:575-576. [PMID: 37081321 DOI: 10.1038/s41594-023-00972-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023]
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14
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He Q, Baranovskiy AG, Morstadt LM, Lisova AE, Babayeva ND, Lusk BL, Lim CJ, Tahirov TH. Structures of human primosome elongation complexes. Nat Struct Mol Biol 2023; 30:579-583. [PMID: 37069376 PMCID: PMC10268227 DOI: 10.1038/s41594-023-00971-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 03/20/2023] [Indexed: 04/19/2023]
Abstract
The synthesis of RNA-DNA primer by primosome requires coordination between primase and DNA polymerase α subunits, which is accompanied by unknown architectural rearrangements of multiple domains. Using cryogenic electron microscopy, we solved a 3.6 Å human primosome structure caught at an early stage of RNA primer elongation with deoxynucleotides. The structure confirms a long-standing role of primase large subunit and reveals new insights into how primosome is limited to synthesizing short RNA-DNA primers.
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Affiliation(s)
- Qixiang He
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Andrey G Baranovskiy
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
| | - Lucia M Morstadt
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
| | - Alisa E Lisova
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
| | - Nigar D Babayeva
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
| | - Benjamin L Lusk
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Ci Ji Lim
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA.
| | - Tahir H Tahirov
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA.
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Lisova AE, Baranovskiy AG, Morstadt LM, Babayeva ND, Tahirov T. Human DNA polymerase α has a strong mutagenic potential at the initial steps of DNA synthesis. Nucleic Acids Res 2022; 50:12266-12273. [PMID: 36454017 PMCID: PMC9757036 DOI: 10.1093/nar/gkac1101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/16/2022] [Accepted: 11/10/2022] [Indexed: 12/05/2022] Open
Abstract
DNA polymerase α (Polα) is essential for DNA replication initiation and makes a notable contribution to genome mutagenesis. The activity and fidelity of Polα during the early steps of DNA replication have not been well studied. Here we show that at the beginning of DNA synthesis, when extending the RNA primer received from primase, Polα is more mutagenic than during the later DNA elongation steps. Kinetic and binding studies revealed substantially higher activity and affinity to the template:primer when Polα interacts with ribonucleotides of a chimeric RNA-DNA primer. Polα activity greatly varies during first six steps of DNA synthesis, and the bias in the rates of correct and incorrect dNTP incorporation leads to impaired fidelity, especially upon the second step of RNA primer extension. Furthermore, increased activity and stability of Polα/template:primer complexes containing RNA-DNA primers result in higher efficiency of mismatch extension.
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Affiliation(s)
| | | | - Lucia M Morstadt
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Nigar D Babayeva
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Tahir H Tahirov
- To whom correspondence should be addressed. Tel: +1 402 559 7608; Fax: +1 402 559 3739;
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