1
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Batenburg NL, Sowa DJ, Walker JR, Andres SN, Zhu XD. CSB and SMARCAL1 compete for RPA32 at stalled forks and differentially control the fate of stalled forks in BRCA2-deficient cells. Nucleic Acids Res 2024; 52:5067-5087. [PMID: 38416570 PMCID: PMC11109976 DOI: 10.1093/nar/gkae154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 02/14/2024] [Accepted: 02/19/2024] [Indexed: 03/01/2024] Open
Abstract
CSB (Cockayne syndrome group B) and SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent, regulator of chromatin, subfamily A-like 1) are DNA translocases that belong to the SNF2 helicase family. They both are enriched at stalled replication forks. While SMARCAL1 is recruited by RPA32 to stalled forks, little is known about whether RPA32 also regulates CSB's association with stalled forks. Here, we report that CSB directly interacts with RPA, at least in part via a RPA32C-interacting motif within the N-terminal region of CSB. Modeling of the CSB-RPA32C interaction suggests that CSB binds the RPA32C surface previously shown to be important for binding of UNG2 and SMARCAL1. We show that this interaction is necessary for promoting fork slowing and fork degradation in BRCA2-deficient cells but dispensable for mediating restart of stalled forks. CSB competes with SMARCAL1 for RPA32 at stalled forks and acts non-redundantly with SMARCAL1 to restrain fork progression in response to mild replication stress. In contrast to CSB stimulated restart of stalled forks, SMARCAL1 inhibits restart of stalled forks in BRCA2-deficient cells, likely by suppressing BIR-mediated repair of collapsed forks. Loss of CSB leads to re-sensitization of SMARCAL1-depleted BRCA2-deficient cells to chemodrugs, underscoring a role of CSB in targeted cancer therapy.
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Affiliation(s)
- Nicole L Batenburg
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Dana J Sowa
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - John R Walker
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Sara N Andres
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Xu-Dong Zhu
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
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2
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Fousek-Schuller VJ, Borgstahl GEO. The Intriguing Mystery of RPA Phosphorylation in DNA Double-Strand Break Repair. Genes (Basel) 2024; 15:167. [PMID: 38397158 PMCID: PMC10888239 DOI: 10.3390/genes15020167] [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: 12/20/2023] [Revised: 01/23/2024] [Accepted: 01/25/2024] [Indexed: 02/25/2024] Open
Abstract
Human Replication Protein A (RPA) was historically discovered as one of the six components needed to reconstitute simian virus 40 DNA replication from purified components. RPA is now known to be involved in all DNA metabolism pathways that involve single-stranded DNA (ssDNA). Heterotrimeric RPA comprises several domains connected by flexible linkers and is heavily regulated by post-translational modifications (PTMs). The structure of RPA has been challenging to obtain. Various structural methods have been applied, but a complete understanding of RPA's flexible structure, its function, and how it is regulated by PTMs has yet to be obtained. This review will summarize recent literature concerning how RPA is phosphorylated in the cell cycle, the structural analysis of RPA, DNA and protein interactions involving RPA, and how PTMs regulate RPA activity and complex formation in double-strand break repair. There are many holes in our understanding of this research area. We will conclude with perspectives for future research on how RPA PTMs control double-strand break repair in the cell cycle.
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Affiliation(s)
| | - Gloria E. O. Borgstahl
- Eppley Institute for Research in Cancer & Allied Diseases, UNMC, Omaha, NE 68198-6805, USA
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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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Sharma T, Kundu N, Kaur S, Shankaraswamy J, Saxena S. Why to target G-quadruplexes using peptides: Next-generation G4-interacting ligands. J Pept Sci 2023; 29:e3491. [PMID: 37009771 DOI: 10.1002/psc.3491] [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: 11/18/2022] [Revised: 03/28/2023] [Accepted: 03/29/2023] [Indexed: 04/04/2023]
Abstract
Guanine-rich oligonucleotides existing in both DNA and RNA are able to fold into four-stranded DNA secondary structures via Hoogsteen type hydrogen-bonding, where four guanines self-assemble into a square planar arrangement, which, when stacked upon each other, results in the formation of higher-order structures called G-quadruplexes. Their distribution is not random; they are more frequently present at telomeres, proto-oncogenic promoters, introns, 5'- and 3'-untranslated regions, stem cell markers, ribosome binding sites and so forth and are associated with various biological functions, all of which play a pivotal role in various incurable diseases like cancer and cellular ageing. Several studies have suggested that G-quadruplexes could not regulate biological processes by themselves; instead, various proteins take part in this regulation and can be important therapeutic targets. There are certain limitations in using whole G4-protein for therapeutics purpose because of its high manufacturing cost, laborious structure prediction, dynamic nature, unavailability for oral administration due to its degradation in the gut and inefficient penetration to reach the target site because of the large size. Hence, biologically active peptides can be the potential candidates for therapeutic intervention instead of the whole G4-protein complex. In this review, we aimed to clarify the biological roles of G4s, how we can identify them throughout the genome via bioinformatics, the proteins interacting with G4s and how G4-interacting peptide molecules may be the potential next-generation ligands for targeting the G4 motifs located in biologically important regions.
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Affiliation(s)
- Taniya Sharma
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Noida, India
| | - Nikita Kundu
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Noida, India
| | - Sarvpreet Kaur
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Noida, India
| | - Jadala Shankaraswamy
- Department of Fruit Science, College of Horticulture, Mojerla, Sri Konda Laxman Telangana State Horticultural University, Budwel, Telangana, India
| | - Sarika Saxena
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Noida, India
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5
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Kang Y, Han YG, Khim KW, Choi WG, Ju MK, Park K, Shin KJ, Chae YC, Choi JH, Kim H, Lee JY. Alteration of replication protein A binding mode on single-stranded DNA by NSMF potentiates RPA phosphorylation by ATR kinase. Nucleic Acids Res 2023; 51:7936-7950. [PMID: 37378431 PMCID: PMC10450186 DOI: 10.1093/nar/gkad543] [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: 12/03/2022] [Revised: 06/07/2023] [Accepted: 06/13/2023] [Indexed: 06/29/2023] Open
Abstract
Replication protein A (RPA), a eukaryotic single-stranded DNA (ssDNA) binding protein, dynamically interacts with ssDNA in different binding modes and plays essential roles in DNA metabolism such as replication, repair, and recombination. RPA accumulation on ssDNA due to replication stress triggers the DNA damage response (DDR) by activating the ataxia telangiectasia and RAD3-related (ATR) kinase, which phosphorylates itself and downstream DDR factors, including RPA. We recently reported that the N-methyl-D-aspartate receptor synaptonuclear signaling and neuronal migration factor (NSMF), a neuronal protein associated with Kallmann syndrome, promotes RPA32 phosphorylation via ATR upon replication stress. However, how NSMF enhances ATR-mediated RPA32 phosphorylation remains elusive. Here, we demonstrate that NSMF colocalizes and physically interacts with RPA at DNA damage sites in vivo and in vitro. Using purified RPA and NSMF in biochemical and single-molecule assays, we find that NSMF selectively displaces RPA in the more weakly bound 8- and 20-nucleotide binding modes from ssDNA, allowing the retention of more stable RPA molecules in the 30-nt binding mode. The 30-nt binding mode of RPA enhances RPA32 phosphorylation by ATR, and phosphorylated RPA becomes stabilized on ssDNA. Our findings provide new mechanistic insight into how NSMF facilitates the role of RPA in the ATR pathway.
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Affiliation(s)
- Yujin Kang
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Ye Gi Han
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Keon Woo Khim
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Woo Gyun Choi
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Min Kyung Ju
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Kibeom Park
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Kyeong Jin Shin
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Young Chan Chae
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Jang Hyun Choi
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
- Institute of Basic Science Center for Genomic Integrity, Ulsan 44919, Republic of Korea
| | - Hongtae Kim
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
- Institute of Basic Science Center for Genomic Integrity, Ulsan 44919, Republic of Korea
| | - Ja Yil Lee
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
- Institute of Basic Science Center for Genomic Integrity, Ulsan 44919, Republic of Korea
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6
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Nasheuer HP, Onwubiko NO. Lagging Strand Initiation Processes in DNA Replication of Eukaryotes-Strings of Highly Coordinated Reactions Governed by Multiprotein Complexes. Genes (Basel) 2023; 14:genes14051012. [PMID: 37239371 DOI: 10.3390/genes14051012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 04/27/2023] [Accepted: 04/28/2023] [Indexed: 05/28/2023] Open
Abstract
In their influential reviews, Hanahan and Weinberg coined the term 'Hallmarks of Cancer' and described genome instability as a property of cells enabling cancer development. Accurate DNA replication of genomes is central to diminishing genome instability. Here, the understanding of the initiation of DNA synthesis in origins of DNA replication to start leading strand synthesis and the initiation of Okazaki fragment on the lagging strand are crucial to control genome instability. Recent findings have provided new insights into the mechanism of the remodelling of the prime initiation enzyme, DNA polymerase α-primase (Pol-prim), during primer synthesis, how the enzyme complex achieves lagging strand synthesis, and how it is linked to replication forks to achieve optimal initiation of Okazaki fragments. Moreover, the central roles of RNA primer synthesis by Pol-prim in multiple genome stability pathways such as replication fork restart and protection of DNA against degradation by exonucleases during double-strand break repair are discussed.
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Affiliation(s)
- Heinz Peter Nasheuer
- Centre for Chromosome Biology, Arts & Science Building, Main Concourse, School of Biological and Chemical Sciences, Biochemistry, University of Galway, Distillery Road, H91 TK33 Galway, Ireland
| | - Nichodemus O Onwubiko
- Centre for Chromosome Biology, Arts & Science Building, Main Concourse, School of Biological and Chemical Sciences, Biochemistry, University of Galway, Distillery Road, H91 TK33 Galway, Ireland
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7
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Onwubiko NO, Scheffel F, Tessmer I, Nasheuer HP. SV40 T antigen helicase domain regions responsible for oligomerisation regulate Okazaki fragment synthesis initiation. FEBS Open Bio 2022; 12:649-663. [PMID: 35073603 PMCID: PMC8886539 DOI: 10.1002/2211-5463.13373] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 12/21/2021] [Accepted: 01/21/2022] [Indexed: 11/11/2022] Open
Affiliation(s)
- Nichodemus O Onwubiko
- Biochemistry School of Biological and Chemical Sciences Biomedical Sciences Building NUI Galway, New Castle Road, Galway, H91 W2TY Ireland
| | - Felicia Scheffel
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef Schneider Strasse 2, D‐97080 Würzburg Germany
| | - Ingrid Tessmer
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef Schneider Strasse 2, D‐97080 Würzburg Germany
| | - Heinz Peter Nasheuer
- Biochemistry School of Biological and Chemical Sciences Biomedical Sciences Building NUI Galway, New Castle Road, Galway, H91 W2TY Ireland
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8
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Peters DK, Erickson KD, Garcea RL. Live Cell Microscopy of Murine Polyomavirus Subnuclear Replication Centers. Viruses 2020; 12:v12101123. [PMID: 33023278 PMCID: PMC7650712 DOI: 10.3390/v12101123] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 09/22/2020] [Accepted: 09/30/2020] [Indexed: 01/24/2023] Open
Abstract
During polyomavirus (PyV) infection, host proteins localize to subnuclear domains, termed viral replication centers (VRCs), to mediate viral genome replication. Although the protein composition and spatial organization of VRCs have been described using high-resolution immunofluorescence microscopy, little is known about the temporal dynamics of VRC formation over the course of infection. We used live cell fluorescence microscopy to analyze VRC formation during murine PyV (MuPyV) infection of a mouse fibroblast cell line that constitutively expresses a GFP-tagged replication protein A complex subunit (GFP-RPA32). The RPA complex forms a heterotrimer (RPA70/32/14) that regulates cellular DNA replication and repair and is a known VRC component. We validated previous observations that GFP-RPA32 relocalized to sites of cellular DNA damage in uninfected cells and to VRCs in MuPyV-infected cells. We then used GFP-RPA32 as a marker of VRC formation and expansion during live cell microscopy of infected cells. VRC formation occurred at variable times post-infection, but the rate of VRC expansion was similar between cells. Additionally, we found that the early viral protein, small TAg (ST), was required for VRC expansion but not VRC formation, consistent with the role of ST in promoting efficient vDNA replication. These results demonstrate the dynamic nature of VRCs over the course of infection and establish an approach for analyzing viral replication in live cells.
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Affiliation(s)
- Douglas K. Peters
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA; (D.K.P.); (K.D.E.)
| | - Kimberly D. Erickson
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA; (D.K.P.); (K.D.E.)
| | - Robert L. Garcea
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA; (D.K.P.); (K.D.E.)
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, CO 80309, USA
- Correspondence:
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9
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Caldwell CC, Spies M. Dynamic elements of replication protein A at the crossroads of DNA replication, recombination, and repair. Crit Rev Biochem Mol Biol 2020; 55:482-507. [PMID: 32856505 PMCID: PMC7821911 DOI: 10.1080/10409238.2020.1813070] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 08/18/2020] [Accepted: 08/18/2020] [Indexed: 01/19/2023]
Abstract
The heterotrimeric eukaryotic Replication protein A (RPA) is a master regulator of numerous DNA metabolic processes. For a long time, it has been viewed as an inert protector of ssDNA and a platform for assembly of various genome maintenance and signaling machines. Later, the modular organization of the RPA DNA binding domains suggested a possibility for dynamic interaction with ssDNA. This modular organization has inspired several models for the RPA-ssDNA interaction that aimed to explain how RPA, the high-affinity ssDNA binding protein, is replaced by the downstream players in DNA replication, recombination, and repair that bind ssDNA with much lower affinity. Recent studies, and in particular single-molecule observations of RPA-ssDNA interactions, led to the development of a new model for the ssDNA handoff from RPA to a specific downstream factor where not only stability and structural rearrangements but also RPA conformational dynamics guide the ssDNA handoff. Here we will review the current knowledge of the RPA structure, its dynamic interaction with ssDNA, and how RPA conformational dynamics may be influenced by posttranslational modification and proteins that interact with RPA, as well as how RPA dynamics may be harnessed in cellular decision making.
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Affiliation(s)
- Colleen C. Caldwell
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - Maria Spies
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
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10
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Onwubiko NO, Borst A, Diaz SA, Passkowski K, Scheffel F, Tessmer I, Nasheuer HP. SV40 T antigen interactions with ssDNA and replication protein A: a regulatory role of T antigen monomers in lagging strand DNA replication. Nucleic Acids Res 2020; 48:3657-3677. [PMID: 32128579 PMCID: PMC7144908 DOI: 10.1093/nar/gkaa138] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 02/14/2020] [Accepted: 02/26/2020] [Indexed: 01/08/2023] Open
Abstract
DNA replication is a central process in all living organisms. Polyomavirus DNA replication serves as a model system for eukaryotic DNA replication and has considerably contributed to our understanding of basic replication mechanisms. However, the details of the involved processes are still unclear, in particular regarding lagging strand synthesis. To delineate the complex mechanism of coordination of various cellular proteins binding simultaneously or consecutively to DNA to initiate replication, we investigated single-stranded DNA (ssDNA) interactions by the SV40 large T antigen (Tag). Using single molecule imaging by atomic force microscopy (AFM) combined with biochemical and spectroscopic analyses we reveal independent activity of monomeric and oligomeric Tag in high affinity binding to ssDNA. Depending on ssDNA length, we obtain dissociation constants for Tag-ssDNA interactions (KD values of 10–30 nM) that are in the same order of magnitude as ssDNA binding by human replication protein A (RPA). Furthermore, we observe the formation of RPA-Tag-ssDNA complexes containing hexameric as well as monomeric Tag forms. Importantly, our data clearly show stimulation of primase function in lagging strand Okazaki fragment synthesis by monomeric Tag whereas hexameric Tag inhibits the reaction, redefining DNA replication initiation on the lagging strand.
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Affiliation(s)
- Nichodemus O Onwubiko
- Biochemistry, School of Natural Sciences, Center for Chromosome Biology, Biomedical SciencesBuilding, NUI Galway, New Castle Road, Galway, Ireland
| | - Angela Borst
- Rudolf Virchow Center for Experimental Biomedicine, University ofWürzburg, Josef Schneider Strasse 2, 97080 Würzburg, Germany
| | - Suraya A Diaz
- Biochemistry, School of Natural Sciences, Center for Chromosome Biology, Biomedical SciencesBuilding, NUI Galway, New Castle Road, Galway, Ireland
| | - Katharina Passkowski
- Rudolf Virchow Center for Experimental Biomedicine, University ofWürzburg, Josef Schneider Strasse 2, 97080 Würzburg, Germany
| | - Felicia Scheffel
- Rudolf Virchow Center for Experimental Biomedicine, University ofWürzburg, Josef Schneider Strasse 2, 97080 Würzburg, Germany
| | - Ingrid Tessmer
- Rudolf Virchow Center for Experimental Biomedicine, University ofWürzburg, Josef Schneider Strasse 2, 97080 Würzburg, Germany
| | - Heinz P Nasheuer
- Biochemistry, School of Natural Sciences, Center for Chromosome Biology, Biomedical SciencesBuilding, NUI Galway, New Castle Road, Galway, Ireland
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11
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Lin T, Scott BL, Hoppe AD, Chakravarty S. FRETting about the affinity of bimolecular protein-protein interactions. Protein Sci 2019; 27:1850-1856. [PMID: 30052312 DOI: 10.1002/pro.3482] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 07/05/2018] [Accepted: 07/12/2018] [Indexed: 01/19/2023]
Abstract
Fluorescence resonance energy transfer (FRET) is a powerful tool to study macromolecular interactions such as protein-protein interactions (PPIs). Fluorescent protein (FP) fusions enable FRET-based PPI analysis of signaling pathways and molecular structure in living cells. Despite FRET's importance in PPI studies, FRET has seen limited use in quantifying the affinities of PPIs in living cells. Here, we have explored the relationship between FRET efficiency and PPI affinity over a wide range when expressed from a single plasmid system in Escherichia coli. Using live-cell microscopy and a set of 20 pairs of small interacting proteins, belonging to different structural folds and interaction affinities, we demonstrate that FRET efficiency can reliably measure the dissociation constant (KD ) over a range of mM to nM. A 10-fold increase in the interaction affinity results in 0.05 unit increase in FRET efficiency, providing sufficient resolution to quantify large affinity differences (> 10-fold) using live-cell FRET. This approach provides a rapid and simple strategy for assessment of PPI affinities over a wide range and will have utility for high-throughput analysis of protein interactions.
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Affiliation(s)
- Tao Lin
- Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota, 57007
| | - Brandon L Scott
- Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota, 57007
| | - Adam D Hoppe
- Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota, 57007.,BioSNTR, Brookings, South Dakota, 57007
| | - Suvobrata Chakravarty
- Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota, 57007.,BioSNTR, Brookings, South Dakota, 57007
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12
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Erickson KD, Garcea RL. Viral replication centers and the DNA damage response in JC virus-infected cells. Virology 2019; 528:198-206. [PMID: 30811999 DOI: 10.1016/j.virol.2018.12.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 12/19/2018] [Accepted: 12/19/2018] [Indexed: 01/09/2023]
Abstract
JCV is a human polyomavirus (PyV) that establishes a persistent infection in its host. Current immunomodulatory therapies, such as Natalizumab for multiple sclerosis, can result in JCV reactivation, leading to the debilitating brain disease progressive multifocal leukoencephalopathy (PML). JCV is among the viruses that recruit and modulate the host DNA damage response (DDR) to replicate its genome. We have identified host proteins recruited to the nuclear sites of JC viral DNA (vDNA) replication using three cell types susceptible to infection in vitro. Using confocal microscopy, we found that JCV recruited a similar repertoire of host DDR proteins to these replication sites previously observed for other PyVs. Electron tomography of JCV "virus factories" showed structural features like those described for murine PyV. These results confirm and extend previous observations for PyVs to JCV emphasizing a similar replication strategy among members of this virus family.
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Affiliation(s)
- Kimberly D Erickson
- The BioFrontiers Institute, University of Colorado, Boulder, CO 80309, United States
| | - Robert L Garcea
- The Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, United States; The BioFrontiers Institute, University of Colorado, Boulder, CO 80309, United States.
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13
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Szambowska A, Tessmer I, Prus P, Schlott B, Pospiech H, Grosse F. Cdc45-induced loading of human RPA onto single-stranded DNA. Nucleic Acids Res 2017; 45:3217-3230. [PMID: 28100698 PMCID: PMC5389570 DOI: 10.1093/nar/gkw1364] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 01/02/2017] [Indexed: 11/14/2022] Open
Abstract
Cell division cycle protein 45 (Cdc45) is an essential component of the eukaryotic replicative DNA helicase. We found that human Cdc45 forms a complex with the single-stranded DNA (ssDNA) binding protein RPA. Moreover, it actively loads RPA onto nascent ssDNA. Pull-down assays and surface plasmon resonance studies revealed that Cdc45-bound RPA complexed with ssDNA in the 8–10 nucleotide binding mode, but dissociated when RPA covered a 30-mer. Real-time analysis of RPA-ssDNA binding demonstrated that Cdc45 catalytically loaded RPA onto ssDNA. This placement reaction required physical contacts of Cdc45 with the RPA70A subdomain. Our results imply that Cdc45 controlled stabilization of the 8-nt RPA binding mode, the subsequent RPA transition into 30-mer mode and facilitated an ordered binding to ssDNA. We propose that a Cdc45-mediated loading guarantees a seamless deposition of RPA on newly emerging ssDNA at the nascent replication fork.
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Affiliation(s)
- Anna Szambowska
- Research Group Biochemistry, Leibniz Institute on Aging-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany
| | - Ingrid Tessmer
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef Schneider Strasse 2, D-97080 Würzburg, Germany
| | - Piotr Prus
- Biocenter Oulu, P.O. Box 5000, 90014 University of Oulu, Finland
| | - Bernhard Schlott
- Research Group Biochemistry, Leibniz Institute on Aging-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.,Proteomics Core Facility, Leibniz Institute on Aging-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany
| | - Helmut Pospiech
- Research Group Biochemistry, Leibniz Institute on Aging-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.,Faculty of Biochemistry and Molecular Medicine, P.O. Box 5000, 90014 University of Oulu, Finland
| | - Frank Grosse
- Research Group Biochemistry, Leibniz Institute on Aging-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.,Center for Molecular Biomedicine, Friedrich-Schiller University, Biochemistry Department, Jena, Germany
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14
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Kashima D, Kawade R, Nagamune T, Kawahara M. A Chemically Inducible Helper Module for Detecting Protein–Protein Interactions with Tunable Sensitivity Based on KIPPIS. Anal Chem 2017; 89:4824-4830. [DOI: 10.1021/acs.analchem.6b04063] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Daiki Kashima
- Department of Chemistry and
Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Raiji Kawade
- Department of Chemistry and
Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Teruyuki Nagamune
- Department of Chemistry and
Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Masahiro Kawahara
- Department of Chemistry and
Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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15
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Krasikova YS, Rechkunova NI, Lavrik OI. Replication protein A as a major eukaryotic single-stranded DNA-binding protein and its role in DNA repair. Mol Biol 2016. [DOI: 10.1134/s0026893316030080] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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16
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Lloyd NR, Dickey TH, Hom RA, Wuttke DS. Tying up the Ends: Plasticity in the Recognition of Single-Stranded DNA at Telomeres. Biochemistry 2016; 55:5326-40. [PMID: 27575340 PMCID: PMC5656232 DOI: 10.1021/acs.biochem.6b00496] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Telomeres terminate nearly exclusively in single-stranded DNA (ssDNA) overhangs comprised of the G-rich 3' end. This overhang varies widely in length from species to species, ranging from just a few bases to several hundred nucleotides. These overhangs are not merely a remnant of DNA replication but rather are the result of complex further processing. Proper management of the telomeric overhang is required both to deter the action of the DNA damage machinery and to present the ends properly to the replicative enzyme telomerase. This Current Topic addresses the biochemical and structural features used by the proteins that manage these variable telomeric overhangs. The Pot1 protein tightly binds the single-stranded overhang, preventing DNA damage sensors from binding. Pot1 also orchestrates the access of telomerase to that same substrate. The remarkable plasticity of the binding interface exhibited by the Schizosaccharomyces pombe Pot1 provides mechanistic insight into how these roles may be accomplished, and disease-associated mutations clustered around the DNA-binding interface in the hPOT1 highlight the importance of this function. The budding yeast Cdc13-Stn1-Ten1, a telomeric RPA complex closely associated with telomere function, also interacts with ssDNA in a fashion that allows degenerate sequences to be recognized. A related human complex composed of hCTC1, hSTN1, and hTEN1 has recently emerged with links to both telomere maintenance and general DNA replication and also exhibits mutations associated with telomere pathologies. Overall, these sequence-specific ssDNA binders exhibit a range of recognition properties that allow them to perform their unique biological functions.
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Affiliation(s)
- Neil R. Lloyd
- Department of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309-0596, USADepartment of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309, USA
| | | | - Robert A. Hom
- Department of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309-0596, USADepartment of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Deborah S. Wuttke
- Department of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309-0596, USADepartment of Chemistry and Biochemistry, 596 UCB, University of Colorado Boulder, Boulder, CO 80309, USA
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17
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Archaeal DNA Replication Origins and Recruitment of the MCM Replicative Helicase. DNA REPLICATION ACROSS TAXA 2016; 39:169-90. [DOI: 10.1016/bs.enz.2016.03.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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18
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Zhou C, Pourmal S, Pavletich NP. Dna2 nuclease-helicase structure, mechanism and regulation by Rpa. eLife 2015; 4. [PMID: 26491943 PMCID: PMC4716839 DOI: 10.7554/elife.09832] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/20/2015] [Indexed: 12/04/2022] Open
Abstract
The Dna2 nuclease-helicase maintains genomic integrity by processing DNA double-strand breaks, Okazaki fragments and stalled replication forks. Dna2 requires ssDNA ends, and is dependent on the ssDNA-binding protein Rpa, which controls cleavage polarity. Here we present the 2.3 Å structure of intact mouse Dna2 bound to a 15-nucleotide ssDNA. The nuclease active site is embedded in a long, narrow tunnel through which the DNA has to thread. The helicase domain is required for DNA binding but not threading. We also present the structure of a flexibly-tethered Dna2-Rpa interaction that recruits Dna2 to Rpa-coated DNA. We establish that a second Dna2-Rpa interaction is mutually exclusive with Rpa-DNA interactions and mediates the displacement of Rpa from ssDNA. This interaction occurs at the nuclease tunnel entrance and the 5’ end of the Rpa-DNA complex. Hence, it only displaces Rpa from the 5’ but not 3’ end, explaining how Rpa regulates cleavage polarity. DOI:http://dx.doi.org/10.7554/eLife.09832.001 DNA carries the genetic information that is essential for organisms to survive and reproduce. It is made of two strands that twist together to form a double helix. However, these strands can be damaged when the DNA is copied before a cell divides, or by exposure to radiation or hazardous chemicals. To prevent this damage from causing serious harm to an organism, cells activate processes that rapidly repair the damaged DNA. “Homologous recombination” is one way in which cells can repair damage that has caused both strands of the DNA to break in a particular place. In the first step, several enzymes trim one of the two DNA strands at each broken end to leave single stranded “tails”. Dna2 is one enzyme that is involved in making these tails, but it can only bind to single-stranded DNA so it only acts after another enzyme has made some initial cuts. The exposed single stranded DNA then searches for an intact copy of itself elsewhere in the genome, which promotes its repair. It is important that only one of the two DNA strands is trimmed at each end otherwise the repair will fail. A protein called Rpa is bound to the DNA and is required for Dna2 to correctly trim the DNA. However, it is not clear exactly how Rpa2 regulates Dna2. Zhou et al. used a technique called X-ray crystallography to analyze the three-dimensional structures of Dna2 when it is bound to single stranded DNA and when it is bound to Rpa. The experiments show that Dna2 adopts a cylindrical shape with a tunnel through which the single-stranded DNA passes through. The region of Dna2 that is capable of trimming DNA – which is called the nuclease domain – is embedded within the tunnel. The entrance to the tunnel is too narrow to allow double-stranded DNA to enter, so this explains why Dna2 can only act on double-stranded DNA that already has a small single-stranded section at the end. Inside the tunnel, Dna2 displaces Rpa from one of the strands, which allows Dna2 to trim the DNA. However, other molecules of Rpa remain firmly bound to the other strand to protect it from Dna2. These enzymes also act in a similar way to trim DNA before it is copied in preparation for cell division. Zhou et al.’s findings provide an explanation for how Rpa determines which strand of DNA is trimmed by Dna2. Further work is needed to understand how Dna2 and Rpa work with other enzymes to trim DNA. DOI:http://dx.doi.org/10.7554/eLife.09832.002
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Affiliation(s)
- Chun Zhou
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Sergei Pourmal
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Nikola P Pavletich
- Howard Hughes Medical Institute, Memorial Sloan-Kettering Cancer Center, New York, United States
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19
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Brosey CA, Soss SE, Brooks S, Yan C, Ivanov I, Dorai K, Chazin WJ. Functional dynamics in replication protein A DNA binding and protein recruitment domains. Structure 2015; 23:1028-38. [PMID: 26004442 DOI: 10.1016/j.str.2015.04.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 03/30/2015] [Accepted: 04/03/2015] [Indexed: 11/29/2022]
Abstract
Replication Protein A (RPA) is an essential scaffold for many DNA processing machines; its function relies on its modular architecture. Here, we report (15)N-nuclear magnetic resonance heteronuclear relaxation analysis to characterize the movements of single-stranded (ss) DNA binding and protein interaction modules in the RPA70 subunit. Our results provide direct evidence for coordination of the motion of the tandem RPA70AB ssDNA binding domains. Moreover, binding of ssDNA substrate is found to cause dramatic reorientation and full coupling of inter-domain motion. In contrast, the RPA70N protein interaction domain remains structurally and dynamically independent of RPA70AB regardless of binding of ssDNA. This autonomy of motion between the 70N and 70AB modules supports a model in which the two binding functions of RPA are mediated fully independently, but remain differentially coordinated depending on the length of their flexible tethers. A critical role for linkers between the globular domains in determining the functional dynamics of RPA is proposed.
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Affiliation(s)
- Chris A Brosey
- Departments of Biochemistry and Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, TN 37232-8725, USA
| | - Sarah E Soss
- Departments of Biochemistry and Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, TN 37232-8725, USA
| | - Sonja Brooks
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Chunli Yan
- Department of Chemistry, Georgia State University, Atlanta, GA 30302-4098, USA
| | - Ivaylo Ivanov
- Department of Chemistry, Georgia State University, Atlanta, GA 30302-4098, USA
| | - Kavita Dorai
- Department of Physics, Indian Institute of Science Education and Research (IISER), Mohali, Sector 81 Manauli PO, SAS Nagar, Punjab 140306, India
| | - Walter J Chazin
- Departments of Biochemistry and Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, TN 37232-8725, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37232, USA.
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20
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An P, Brodsky JL, Pipas JM. The conserved core enzymatic activities and the distinct dynamics of polyomavirus large T antigens. Arch Biochem Biophys 2015; 573:23-31. [PMID: 25752954 PMCID: PMC4865250 DOI: 10.1016/j.abb.2015.02.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 02/18/2015] [Accepted: 02/19/2015] [Indexed: 01/02/2023]
Abstract
Several human polyomaviruses including JCV, BKV and TSV are associated with diseases, particularly in immunosuppressed patients. While the large T antigen (LT) encoded by the monkey polyomavirus SV40 is well studied, and possesses intrinsic ATPase and DNA helicase activities, the LTs of the human polyomaviruses are relatively uncharacterized. In order to evaluate whether these enzymatic activities, which are required for viral DNA replication, are conserved between polyomaviruses, we performed a comparative study using the LTs from JCV, TSV and SV40. The ATPase and DNA helicase activities and the interaction with the cellular tumor suppressor p53 were assayed for the purified Zn-ATPase domains of the three LTs. We found that all Zn-ATPases were active ATPases. The Zn-ATPase domains also functioned as DNA helicases, although the measured kinetic constants differed among the three proteins. In addition, when tested against four small molecule ATPase inhibitors, the Zn-ATPase domains of TSV was more resistant than that of SV40 and JCV. Our results show that, while LTs from JCV and TSV share the core ATPase and DNA helicase activities, they possess important functional differences that might translate into their respective abilities to infect and replicate in hosts.
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Affiliation(s)
- Ping An
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - James M Pipas
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
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21
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Ning B, Feldkamp MD, Cortez D, Chazin WJ, Friedman KL, Fanning E. Simian virus Large T antigen interacts with the N-terminal domain of the 70 kD subunit of Replication Protein A in the same mode as multiple DNA damage response factors. PLoS One 2015; 10:e0116093. [PMID: 25706313 PMCID: PMC4337903 DOI: 10.1371/journal.pone.0116093] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/04/2014] [Indexed: 11/18/2022] Open
Abstract
Simian virus 40 (SV40) serves as an important model organism for studying eukaryotic DNA replication. Its helicase, Large T-antigen (Tag), is a multi-functional protein that interacts with multiple host proteins, including the ubiquitous ssDNA binding protein Replication Protein A (RPA). Tag recruits RPA, actively loads it onto the unwound DNA, and together they promote priming of the template. Although interactions of Tag with RPA have been mapped, no interaction between Tag and the N-terminal protein interaction domain of the RPA 70kDa subunit (RPA70N) has been reported. Here we provide evidence of direct physical interaction of Tag with RPA70N and map the binding sites using a series of pull-down and mutational experiments. In addition, a monoclonal anti-Tag antibody, the epitope of which overlaps with the binding site, blocks the binding of Tag to RPA70N. We use NMR chemical shift perturbation analysis to show that Tag uses the same basic cleft in RPA70N as multiple of DNA damage response proteins. Mutations in the binding sites of both RPA70N and Tag demonstrate that specific charge reversal substitutions in either binding partner strongly diminish the interaction. These results expand the known repertoire of contacts between Tag and RPA, which mediate the many critical roles of Tag in viral replication.
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Affiliation(s)
- Boting Ning
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Michael D. Feldkamp
- Departments of Biochemistry, Chemistry, and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - David Cortez
- Department of Biochemistry, Vanderbilt University Medical School, Nashville, Tennessee, United States of America
| | - Walter J. Chazin
- Departments of Biochemistry, Chemistry, and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail: (KLF); (WJC)
| | - Katherine L. Friedman
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail: (KLF); (WJC)
| | - Ellen Fanning
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
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22
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Guilliam TA, Jozwiakowski SK, Ehlinger A, Barnes RP, Rudd SG, Bailey LJ, Skehel JM, Eckert KA, Chazin WJ, Doherty AJ. Human PrimPol is a highly error-prone polymerase regulated by single-stranded DNA binding proteins. Nucleic Acids Res 2014; 43:1056-68. [PMID: 25550423 PMCID: PMC4333378 DOI: 10.1093/nar/gku1321] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
PrimPol is a recently identified polymerase involved in eukaryotic DNA damage tolerance, employed in both re-priming and translesion synthesis mechanisms to bypass nuclear and mitochondrial DNA lesions. In this report, we investigate how the enzymatic activities of human PrimPol are regulated. We show that, unlike other TLS polymerases, PrimPol is not stimulated by PCNA and does not interact with it in vivo. We identify that PrimPol interacts with both of the major single-strand binding proteins, RPA and mtSSB in vivo. Using NMR spectroscopy, we characterize the domains responsible for the PrimPol-RPA interaction, revealing that PrimPol binds directly to the N-terminal domain of RPA70. In contrast to the established role of SSBs in stimulating replicative polymerases, we find that SSBs significantly limit the primase and polymerase activities of PrimPol. To identify the requirement for this regulation, we employed two forward mutation assays to characterize PrimPol's replication fidelity. We find that PrimPol is a mutagenic polymerase, with a unique error specificity that is highly biased towards insertion-deletion errors. Given the error-prone disposition of PrimPol, we propose a mechanism whereby SSBs greatly restrict the contribution of this enzyme to DNA replication at stalled forks, thus reducing the mutagenic potential of PrimPol during genome replication.
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Affiliation(s)
- Thomas A Guilliam
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN1 9RQ, UK
| | - Stanislaw K Jozwiakowski
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN1 9RQ, UK
| | - Aaron Ehlinger
- Departments of Biochemistry and Chemistry and Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Ryan P Barnes
- The Jake Gittlen Laboratories for Cancer Research Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Sean G Rudd
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN1 9RQ, UK
| | - Laura J Bailey
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN1 9RQ, UK
| | - J Mark Skehel
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Kristin A Eckert
- The Jake Gittlen Laboratories for Cancer Research Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Walter J Chazin
- Departments of Biochemistry and Chemistry and Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Aidan J Doherty
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton BN1 9RQ, UK
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23
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Sugitani N, Chazin WJ. Characteristics and concepts of dynamic hub proteins in DNA processing machinery from studies of RPA. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 117:206-211. [PMID: 25542993 DOI: 10.1016/j.pbiomolbio.2014.12.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 12/15/2014] [Accepted: 12/16/2014] [Indexed: 11/26/2022]
Abstract
DNA replication, damage response and repair require the coordinated action of multi-domain proteins operating within dynamic multi-protein machines that act upon the DNA substrate. These modular proteins contain flexible linkers of various lengths, which enable changes in the spatial distribution of the globular domains (architecture) that harbor their essential biochemical functions. This mobile architecture is uniquely suited to follow the evolving substrate landscape present over the course of the specific process performed by the multi-protein machinery. A fundamental advance in understanding of protein machinery is the realization of the pervasive role of dynamics. Not only is the machine undergoing dynamic transformations, but the proteins themselves are flexible and constantly adapting to the progression through the steps of the overall process. Within this dynamic context the activity of the constituent proteins must be coordinated, a role typically played by hub proteins. A number of important characteristics of modular proteins and concepts about the operation of dynamic machinery have been discerned. These provide the underlying basis for the action of the machinery that reads DNA, and responds to and repairs DNA damage. Here, we introduce a number of key characteristics and concepts, including the modularity of the proteins, linkage of weak binding sites, direct competition between sites, and allostery, using the well recognized hub protein replication protein A (RPA).
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Affiliation(s)
- Norie Sugitani
- Center for Structural Biology and Departments of Biochemistry and Chemistry, Vanderbilt University, Nashville, TN, USA
| | - Walter J Chazin
- Center for Structural Biology and Departments of Biochemistry and Chemistry, Vanderbilt University, Nashville, TN, USA.
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24
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Maréchal A, Zou L. RPA-coated single-stranded DNA as a platform for post-translational modifications in the DNA damage response. Cell Res 2014; 25:9-23. [PMID: 25403473 DOI: 10.1038/cr.2014.147] [Citation(s) in RCA: 313] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The Replication Protein A (RPA) complex is an essential regulator of eukaryotic DNA metabolism. RPA avidly binds to single-stranded DNA (ssDNA) through multiple oligonucleotide/oligosaccharide-binding folds and coordinates the recruitment and exchange of genome maintenance factors to regulate DNA replication, recombination and repair. The RPA-ssDNA platform also constitutes a key physiological signal which activates the master ATR kinase to protect and repair stalled or collapsed replication forks during replication stress. In recent years, the RPA complex has emerged as a key target and an important regulator of post-translational modifications in response to DNA damage, which is critical for its genome guardian functions. Phosphorylation and SUMOylation of the RPA complex, and more recently RPA-regulated ubiquitination, have all been shown to control specific aspects of DNA damage signaling and repair by modulating the interactions between RPA and its partners. Here, we review our current understanding of the critical functions of the RPA-ssDNA platform in the maintenance of genome stability and its regulation through an elaborate network of covalent modifications.
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Affiliation(s)
- Alexandre Maréchal
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Lee Zou
- 1] Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA [2] Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
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25
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Hwang H, Kreig A, Calvert J, Lormand J, Kwon Y, Daley JM, Sung P, Opresko PL, Myong S. Telomeric overhang length determines structural dynamics and accessibility to telomerase and ALT-associated proteins. Structure 2014; 22:842-53. [PMID: 24836024 DOI: 10.1016/j.str.2014.03.013] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/07/2014] [Accepted: 03/04/2014] [Indexed: 02/03/2023]
Abstract
The G-rich single-stranded DNA at the 3' end of human telomeres can self-fold into G-quaduplex (GQ). However, telomere lengthening by telomerase or the recombination-based alternative lengthening of telomere (ALT) mechanism requires protein loading on the overhang. Using single-molecule fluorescence spectroscopy, we discovered that lengthening the telomeric overhang also increased the rate of dynamic exchanges between structural conformations. Overhangs with five to seven TTAGGG repeats, compared with four repeats, showed much greater dynamics and accessibility to telomerase binding and activity and loading of the ALT-associated proteins RAD51, WRN, and BLM. Although the eight repeats are highly dynamic, they can fold into two GQs, which limited protein accessibility. In contrast, the telomere-specific protein POT1 is unique in that it binds independently of repeat number. Our results suggest that the telomeric overhang length and dynamics may contribute to the regulation of telomere extension via telomerase action and the ALT mechanism.
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Affiliation(s)
- Helen Hwang
- Bioengineering Department, University of Illinois, 1304 West Springfield Avenue, Urbana, IL 61801, USA; Medical Scholars Program, University of Illinois, 506 South Matthews Avenue, Urbana, IL 61801, USA
| | - Alex Kreig
- Bioengineering Department, University of Illinois, 1304 West Springfield Avenue, Urbana, IL 61801, USA
| | - Jacob Calvert
- Bioengineering Department, University of Illinois, 1304 West Springfield Avenue, Urbana, IL 61801, USA
| | - Justin Lormand
- Department of Environmental and Occupational Health, University of Pittsburgh, 100 Technology Drive, Suite 326, BRIDG, Pittsburgh, PA 15219, USA
| | - Yongho Kwon
- Department of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar Street, P.O. Box 208024, New Haven, CT 06520, USA
| | - James M Daley
- Department of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar Street, P.O. Box 208024, New Haven, CT 06520, USA
| | - Patrick Sung
- Department of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar Street, P.O. Box 208024, New Haven, CT 06520, USA
| | - Patricia L Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh, 100 Technology Drive, Suite 326, BRIDG, Pittsburgh, PA 15219, USA
| | - Sua Myong
- Bioengineering Department, University of Illinois, 1304 West Springfield Avenue, Urbana, IL 61801, USA; Institute for Genomic Biology, University of Illinois, 1206 West Gregory Street, Urbana, IL 61801, USA; Physics Frontier Center (Center of Physics for Living Cells), University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA.
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26
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Modulation of human α-synuclein aggregation by a combined effect of calcium and dopamine. Neurobiol Dis 2013; 63:115-28. [PMID: 24269918 DOI: 10.1016/j.nbd.2013.11.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 10/17/2013] [Accepted: 11/12/2013] [Indexed: 11/21/2022] Open
Abstract
Parkinson's disease is characterized by the deposition of aggregated α-syn and its familial mutants into Lewy bodies leading to death of dopaminergic neurons. α-syn is involved in Ca(II) and dopamine (DA) signaling and their adequate balance inside neuronal cytoplasm is essential for maintaining healthy dopaminergic neurons. We have probed the binding energetics of Ca(II) and DA to human α-syn and its familial mutants A30P, A53T and E46K using isothermal titration calorimetry and have investigated the conformational and aggregation aspects using circular dichroism and fluorescence spectroscopy. While binding of Ca(II) to α-syn and its familial mutants was observed to be endothermic in nature, interaction of DA with α-syn was not detectable. Ca(II) enhanced fibrillation of α-syn and its familial mutants while DA promoted the formation of oligomers. However, Ca(II) and DA together critically favored the formation of protofibrils that are more cytotoxic than the mature fibrils. Using fluorescently labeled cysteine mutant A90C, we have shown that different aggregating species of α-syn formed in the presence of Ca(II) and DA are internalized into the human neuroblastoma cells with different rates and are responsible for the differential cytotoxicity depending on their nature. The findings put together suggest that an interplay between the concentrations of Ca(II), DA and α-syn can critically regulate the formation of various aggregating species responsible for the survival of dopaminergic neurons. Modulating this balance leading to either complete suppression of α-syn aggregation or promoting the formation of mature fibrils could be used as a strategy for the development of drugs to cure Parkinson's disease.
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27
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Abstract
Rfa2 is a ssDNA (single-stranded DNA)-binding protein that plays an important role in DNA replication, recombination and repair. Rfa2 is regulated by phosphorylation, which alters its protein–protein interaction and protein–DNA interaction. In the present study, we found that the Pph3–Psy2 phosphatase complex is responsible for Rfa2 dephosphorylation both during normal G1-phase and under DNA replication stress in Candida albicans. Phosphorylated Rfa2 extracted from pph3Δ or psy2Δ G1 cells exhibited diminished binding affinity to dsDNA (double-stranded DNA) but not to ssDNA. We also discovered that Cdc28 (cell division cycle 28) and Mec1 are responsible for Rfa2 phosphorylation in G1-phase and under DNA replication stress respectively. Moreover, MS revealed that the domain of Rfa2 that was phosphorylated in G1-phase differed from that phosphorylated under the stress conditions. The results of the present study imply that differential phosphorylation plays a crucial role in RPA (replication protein A) regulation.
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28
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An P, Sáenz Robles MT, Pipas JM. Large T antigens of polyomaviruses: amazing molecular machines. Annu Rev Microbiol 2013; 66:213-36. [PMID: 22994493 DOI: 10.1146/annurev-micro-092611-150154] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The large tumor antigen (T antigen) encoded by simian virus 40 is an amazing molecular machine because it orchestrates viral infection by modulating multiple fundamental viral and cellular processes. T antigen is required for viral DNA replication, transcription, and virion assembly. In addition, T antigen targets multiple cellular pathways, including those that regulate cell proliferation, cell death, and the inflammatory response. Ectopic T antigen expression results in the immortalization and transformation of many cell types in culture and T antigen induces neoplasia when expressed in rodents. The analysis of the mechanisms by which T antigen carries out its many functions has proved to be a powerful way of gaining insights into cell biology. The accelerating pace at which new polyomaviruses are being discovered provides a collection of novel T antigens that, like simian virus 40, can be used to discover and study key cellular regulatory systems.
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Affiliation(s)
- Ping An
- Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260, USA
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29
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Brosey CA, Yan C, Tsutakawa SE, Heller WT, Rambo RP, Tainer JA, Ivanov I, Chazin WJ. A new structural framework for integrating replication protein A into DNA processing machinery. Nucleic Acids Res 2013; 41:2313-27. [PMID: 23303776 PMCID: PMC3575853 DOI: 10.1093/nar/gks1332] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
By coupling the protection and organization of single-stranded DNA (ssDNA) with recruitment and alignment of DNA processing factors, replication protein A (RPA) lies at the heart of dynamic multi-protein DNA processing machinery. Nevertheless, how RPA coordinates biochemical functions of its eight domains remains unknown. We examined the structural biochemistry of RPA’s DNA-binding activity, combining small-angle X-ray and neutron scattering with all-atom molecular dynamics simulations to investigate the architecture of RPA’s DNA-binding core. The scattering data reveal compaction promoted by DNA binding; DNA-free RPA exists in an ensemble of states with inter-domain mobility and becomes progressively more condensed and less dynamic on binding ssDNA. Our results contrast with previous models proposing RPA initially binds ssDNA in a condensed state and becomes more extended as it fully engages the substrate. Moreover, the consensus view that RPA engages ssDNA in initial, intermediate and final stages conflicts with our data revealing that RPA undergoes two (not three) transitions as it binds ssDNA with no evidence for a discrete intermediate state. These results form a framework for understanding how RPA integrates the ssDNA substrate into DNA processing machinery, provides substrate access to its binding partners and promotes the progression and selection of DNA processing pathways.
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Affiliation(s)
- Chris A Brosey
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA
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30
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Fan J, Pavletich NP. Structure and conformational change of a replication protein A heterotrimer bound to ssDNA. Genes Dev 2012; 26:2337-47. [PMID: 23070815 DOI: 10.1101/gad.194787.112] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Replication protein A (RPA) is the main eukaryotic ssDNA-binding protein with essential roles in DNA replication, recombination, and repair. RPA maintains the DNA as single-stranded and also interacts with other DNA-processing proteins, coordinating their assembly and disassembly on DNA. RPA binds to ssDNA in two conformational states with opposing affinities for DNA and proteins. The RPA-protein interactions are compatible with a low DNA affinity state that involves DNA-binding domain A (DBD-A) and DBD-B but not with the high DNA affinity state that additionally engages DBD-C and DBD-D. The structure of the high-affinity RPA-ssDNA complex reported here shows a compact quaternary structure held together by a four-way interface between DBD-B, DBD-C, the intervening linker (BC linker), and ssDNA. The BC linker binds into the DNA-binding groove of DBD-B, mimicking DNA. The associated conformational change and partial occlusion of the DBD-A-DBA-B protein-protein interaction site establish a mechanism for the allosteric coupling of RPA-DNA and RPA-protein interactions.
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Affiliation(s)
- Jie Fan
- Sloan-Kettering Division, Joan and Sanford I. Weill Graduate School of Medical Sciences, Cornell University, New York, New York 10065, USA
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31
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Simmons DT. Modeling of the SV40 DNA Replication Machine. Genes (Basel) 2012; 3:742-58. [PMID: 24705083 PMCID: PMC3902795 DOI: 10.3390/genes3040742] [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: 10/07/2012] [Revised: 10/24/2012] [Accepted: 11/04/2012] [Indexed: 12/04/2022] Open
Abstract
The mechanism of SV40 DNA replication is certainly not completely understood. The proteins that are necessary for replication have been known for quite some time, but how they work together to form a nanomachine capable of faithfully replicating the virus DNA is only partially understood. Some of the proteins involved have been crystallized and their 3D structures determined, and several EM reconstructions of SV40 T antigen have been generated. In addition, there is a fair amount of biochemical data that pinpoints the sites of interaction between various proteins. With this information, various models were assembled that show how the SV40 DNA replication nanomachine could be structured in three dimensional space. This process was aided by the use of a 3D docking program as well as fitting of structures. The advantage of the availability of these models is that they are experimentally testable and they provide an insight into how the replication machine could work. Another advantage is that it is possible to quickly compare newly published structures to the models in order to come up with improved models.
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Affiliation(s)
- Daniel T Simmons
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA.
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32
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Zhou B, Arnett DR, Yu X, Brewster A, Sowd GA, Xie CL, Vila S, Gai D, Fanning E, Chen XS. Structural basis for the interaction of a hexameric replicative helicase with the regulatory subunit of human DNA polymerase α-primase. J Biol Chem 2012; 287:26854-66. [PMID: 22700977 DOI: 10.1074/jbc.m112.363655] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA polymerase α-primase (Pol-prim) plays an essential role in eukaryotic DNA replication, initiating synthesis of the leading strand and of each Okazaki fragment on the lagging strand. Pol-prim is composed of a primase heterodimer that synthesizes an RNA primer, a DNA polymerase subunit that extends the primer, and a regulatory B-subunit (p68) without apparent enzymatic activity. Pol-prim is thought to interact with eukaryotic replicative helicases, forming a dynamic multiprotein assembly that displays primosome activity. At least three subunits of Pol-prim interact physically with the hexameric replicative helicase SV40 large T antigen, constituting a simple primosome that is active in vitro. However, structural understanding of these interactions and their role in viral chromatin replication in vivo remains incomplete. Here, we report the detailed large T antigen-p68 interface, as revealed in a co-crystal structure and validated by site-directed mutagenesis, and we demonstrate its functional importance in activating the SV40 primosome in cell-free reactions with purified Pol-prim, as well as in monkey cells in vivo.
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Affiliation(s)
- Bo Zhou
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, California 90089, USA
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33
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Prakash A, Borgstahl GEO. The structure and function of replication protein A in DNA replication. Subcell Biochem 2012; 62:171-96. [PMID: 22918586 DOI: 10.1007/978-94-007-4572-8_10] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In all organisms from bacteria and archaea to eukarya, single-stranded DNA binding proteins play an essential role in most, if not all, nuclear metabolism involving single-stranded DNA (ssDNA). Replication protein A (RPA), the major eukaryotic ssDNA binding protein, has two important roles in DNA metabolism: (1) in binding ssDNA to protect it and to keep it unfolded, and (2) in coordinating the assembly and disassembly of numerous proteins and protein complexes during processes such as DNA replication. Since its discovery as a vital player in the process of replication, RPAs roles in recombination and DNA repair quickly became evident. This chapter summarizes the current understanding of RPA's roles in replication by reviewing the available structural data, DNA-binding properties, interactions with various replication proteins, and interactions with DNA repair proteins when DNA replication is stalled.
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Affiliation(s)
- Aishwarya Prakash
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Given Medical Building, 89 Beaumont Avenue, Burlington, VT, 05405, USA
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34
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Guler GD, Liu H, Vaithiyalingam S, Arnett DR, Kremmer E, Chazin WJ, Fanning E. Human DNA helicase B (HDHB) binds to replication protein A and facilitates cellular recovery from replication stress. J Biol Chem 2011; 287:6469-81. [PMID: 22194613 DOI: 10.1074/jbc.m111.324582] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Maintenance of genomic stability in proliferating cells depends on a network of proteins that coordinate chromosomal replication with DNA damage responses. Human DNA helicase B (HELB or HDHB) has been implicated in chromosomal replication, but its role in this coordinated network remains undefined. Here we report that cellular exposure to UV irradiation, camptothecin, or hydroxyurea induces accumulation of HDHB on chromatin in a dose- and time-dependent manner, preferentially in S phase cells. Replication stress-induced recruitment of HDHB to chromatin is independent of checkpoint signaling but correlates with the level of replication protein A (RPA) recruited to chromatin. We show using purified proteins that HDHB physically interacts with the N-terminal domain of the RPA 70-kDa subunit (RPA70N). NMR spectroscopy and site-directed mutagenesis reveal that HDHB docks on the same RPA70N surface that recruits S phase checkpoint signaling proteins to chromatin. Consistent with this pattern of recruitment, cells depleted of HDHB display reduced recovery from replication stress.
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Affiliation(s)
- Gulfem Dilek Guler
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235-1634, USA
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35
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BID binds to replication protein A and stimulates ATR function following replicative stress. Mol Cell Biol 2011; 31:4298-309. [PMID: 21859891 DOI: 10.1128/mcb.05737-11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Proapoptotic BH3-interacting death domain agonist (BID) regulates apoptosis and the DNA damage response. Following replicative stress, BID associates with proteins of the DNA damage sensor complex, including replication protein A (RPA), ataxia telangiectasia and Rad3 related (ATR), and ATR-interacting protein (ATRIP), and facilitates an efficient DNA damage response. We have found that BID stimulates the association of RPA with components of the DNA damage sensor complex through interaction with the basic cleft of the N-terminal domain of the RPA70 subunit. Disruption of the BID-RPA interaction impairs the association of ATR-ATRIP with chromatin as well as ATR function, as measured by CHK1 activation and recovery of DNA replication following hydroxyurea (HU). We further demonstrate that the association of BID with RPA stimulates the association of ATR-ATRIP to the DNA damage sensor complex. We propose a model in which BID associates with RPA and stimulates the recruitment and/or stabilization of ATR-ATRIP to the DNA damage sensor complex.
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36
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Dragnea V, Arunkumar AI, Lee CW, Giedroc DP, Bauer CE. A Q63E Rhodobacter sphaeroides AppA BLUF domain mutant is locked in a pseudo-light-excited signaling state. Biochemistry 2010; 49:10682-90. [PMID: 21082791 DOI: 10.1021/bi1002162] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The AppA BLUF photoreceptor from Rhodobacter sphaeroides contains a conserved key residue, Gln63, that is thought to undergo a shift in hydrogen-bonding interactions when a bound flavin is light excited. In this study we have characterized two substitution mutants of Gln63 (Q63E, Q63L) in the context of two constructs of the BLUF domain that have differing lengths, AppA1-126 and AppA17-133. Q63L mutations in both constructs exhibit a blue-shifted flavin absorption spectrum as well as a loss of the photocycle. Altered fluorescence emission and fluorescence quenching of the Q63L mutant indicate significant perturbations of hydrogen bonding to the flavin and surrounding amino acids which is confirmed by (1)H-(15)N HSQC NMR spectroscopy. The Q63E substitution mutant is constitutively locked in a lit signaling state as evidenced by a permanent 3 nm red shift of the flavin absorption, quenching of flavin fluorescence emission, analysis of (1)H-(15)N HSQC spectra, and the inability of full-length AppA Q63E to bind to the PpsR repressor. The significance of these findings on the mechanism of light-induced output signaling is discussed.
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Affiliation(s)
- Vladimira Dragnea
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, United States
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37
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Huang H, Zhao K, Arnett DR, Fanning E. A specific docking site for DNA polymerase {alpha}-primase on the SV40 helicase is required for viral primosome activity, but helicase activity is dispensable. J Biol Chem 2010; 285:33475-33484. [PMID: 20685648 PMCID: PMC2963361 DOI: 10.1074/jbc.m110.156240] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 07/31/2010] [Indexed: 11/06/2022] Open
Abstract
Replication of simian virus 40 (SV40) DNA, a model for eukaryotic chromosomal replication, can be reconstituted in vitro using the viral helicase (large tumor antigen, or Tag) and purified human proteins. Tag interacts physically with two cellular proteins, replication protein A and DNA polymerase α-primase (pol-prim), constituting the viral primosome. Like the well characterized primosomes of phages T7 and T4, this trio of proteins coordinates parental DNA unwinding with primer synthesis to initiate the leading strand at the viral origin and each Okazaki fragment on the lagging strand template. We recently determined the structure of a previously unrecognized pol-prim domain (p68N) that docks on Tag, identified the p68N surface that contacts Tag, and demonstrated its vital role in primosome function. Here, we identify the p68N-docking site on Tag by using structure-guided mutagenesis of the Tag helicase surface. A charge reverse substitution in Tag disrupted both p68N-binding and primosome activity but did not affect docking with other pol-prim subunits. Unexpectedly, the substitution also disrupted Tag ATPase and helicase activity, suggesting a potential link between p68N docking and ATPase activity. To assess this possibility, we examined the primosome activity of Tag with a single residue substitution in the Walker B motif. Although this substitution abolished ATPase and helicase activity as expected, it did not reduce pol-prim docking on Tag or primosome activity on single-stranded DNA, indicating that Tag ATPase is dispensable for primosome activity in vitro.
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Affiliation(s)
- Hao Huang
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235-1634
| | - Kun Zhao
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235-1634
| | - Diana R Arnett
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235-1634
| | - Ellen Fanning
- From the Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235-1634.
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38
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Insights into eukaryotic DNA priming from the structure and functional interactions of the 4Fe-4S cluster domain of human DNA primase. Proc Natl Acad Sci U S A 2010; 107:13684-9. [PMID: 20643958 DOI: 10.1073/pnas.1002009107] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
DNA replication requires priming of DNA templates by enzymes known as primases. Although DNA primase structures are available from archaea and bacteria, the mechanism of DNA priming in higher eukaryotes remains poorly understood in large part due to the absence of the structure of the unique, highly conserved C-terminal regulatory domain of the large subunit (p58C). Here, we present the structure of this domain determined to 1.7-A resolution by X-ray crystallography. The p58C structure reveals a novel arrangement of an evolutionarily conserved 4Fe-4S cluster buried deeply within the protein core and is not similar to any known protein structure. Analysis of the binding of DNA to p58C by fluorescence anisotropy measurements revealed a strong preference for ss/dsDNA junction substrates. This approach was combined with site-directed mutagenesis to confirm that the binding of DNA occurs to a distinctively basic surface on p58C. A specific interaction of p58C with the C-terminal domain of the intermediate subunit of replication protein A (RPA32C) was identified and characterized by isothermal titration calorimetry and NMR. Restraints from NMR experiments were used to drive computational docking of the two domains and generate a model of the p58C-RPA32C complex. Together, our results explain functional defects in human DNA primase mutants and provide insights into primosome loading on RPA-coated ssDNA and regulation of primase activity.
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39
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Huang H, Weiner BE, Zhang H, Fuller BE, Gao Y, Wile BM, Zhao K, Arnett DR, Chazin WJ, Fanning E. Structure of a DNA polymerase alpha-primase domain that docks on the SV40 helicase and activates the viral primosome. J Biol Chem 2010; 285:17112-22. [PMID: 20234039 DOI: 10.1074/jbc.m110.116830] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA polymerase alpha-primase (pol-prim) plays a central role in DNA replication in higher eukaryotes, initiating synthesis on both leading and lagging strand single-stranded DNA templates. Pol-prim consists of a primase heterodimer that synthesizes RNA primers, a DNA polymerase that extends them, and a fourth subunit, p68 (also termed B-subunit), that is thought to regulate the complex. Although significant knowledge about single-subunit primases of prokaryotes has accumulated, the functions and regulation of pol-prim remain poorly understood. In the SV40 replication model, the p68 subunit is required for primosome activity and binds directly to the hexameric viral helicase T antigen, suggesting a functional link between T antigen-p68 interaction and primosome activity. To explore this link, we first mapped the interacting regions of the two proteins and discovered a previously unrecognized N-terminal globular domain of p68 (p68N) that physically interacts with the T antigen helicase domain. NMR spectroscopy was used to determine the solution structure of p68N and map its interface with the T antigen helicase domain. Structure-guided mutagenesis of p68 residues in the interface diminished T antigen-p68 interaction, confirming the interaction site. SV40 primosome activity of corresponding pol-prim mutants decreased in proportion to the reduction in p68N-T antigen affinity, confirming that p68-T antigen interaction is vital for primosome function. A model is presented for how this interaction regulates SV40 primosome activity, and the implications of our findings are discussed in regard to the molecular mechanisms of eukaryotic DNA replication initiation.
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Affiliation(s)
- Hao Huang
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37232, USA
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40
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Broderick S, Rehmet K, Concannon C, Nasheuer HP. Eukaryotic single-stranded DNA binding proteins: central factors in genome stability. Subcell Biochem 2010; 50:143-163. [PMID: 20012581 DOI: 10.1007/978-90-481-3471-7_8] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The single-stranded DNA binding proteins (SSBs) are required to maintain the integrity of the genome in all organisms. Replication protein A (RPA) is a nuclear SSB protein found in all eukaryotes and is required for multiple processes in DNA metabolism such as DNA replication, DNA repair, DNA recombination, telomere maintenance and DNA damage signalling. RPA is a heterotrimeric complex, binds ssDNA with high affinity, and interacts specifically with multiple proteins to fulfil its function in eukaryotes. RPA is phosphorylated in a cell cycle and DNA damage-dependent manner with evidence suggesting that phosphorylation has an important function in modulating the cellular DNA damage response. Considering the DNA-binding properties of RPA a mechanism of "molecular counting" to initiate DNA damage-dependent signalling is discussed. Recently a human homologue to the RPA2 subunit, called RPA4, was discovered and RPA4 can substitute for RPA2 in the RPA complex resulting in an "alternative" RPA (aRPA), which can bind to ssDNA with similar affinity as canonical RPA. Additional human SSBs, hSSB1 and hSSB2, were recently identified, with hSSB1 being localized in the nucleus and having implications in DNA repair. Mitochondrial SSBs (mtSSBs) have been found in all eukaryotes studied. mtSSBs are related to prokaryotic SSBs and essential to main the genome stability in eukaryotic mitochondria. Recently human mtSSB was identified as a novel binding partner of p53 and that it is able to stimulate the intrinsic exonuclease activity of p53. These findings and recent results associated with mutations in RPA suggest a link of SSBs to cancer.
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Affiliation(s)
- Sandra Broderick
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, Galway, Ireland
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41
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Kemp MG, Mason AC, Carreira A, Reardon JT, Haring SJ, Borgstahl GEO, Kowalczykowski SC, Sancar A, Wold MS. An alternative form of replication protein a expressed in normal human tissues supports DNA repair. J Biol Chem 2009; 285:4788-97. [PMID: 19996105 DOI: 10.1074/jbc.m109.079418] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Replication protein A (RPA) is a heterotrimeric protein complex required for a large number of DNA metabolic processes, including DNA replication and repair. An alternative form of RPA (aRPA) has been described in which the RPA2 subunit (the 32-kDa subunit of RPA and product of the RPA2 gene) of canonical RPA is replaced by a homologous subunit, RPA4. The normal function of aRPA is not known; however, previous studies have shown that it does not support DNA replication in vitro or S-phase progression in vivo. In this work, we show that the RPA4 gene is expressed in normal human tissues and that its expression is decreased in cancerous tissues. To determine whether aRPA plays a role in cellular physiology, we investigated its role in DNA repair. aRPA interacted with both Rad52 and Rad51 and stimulated Rad51 strand exchange. We also showed that, by using a reconstituted reaction, aRPA can support the dual incision/excision reaction of nucleotide excision repair. aRPA is less efficient in nucleotide excision repair than canonical RPA, showing reduced interactions with the repair factor XPA and no stimulation of XPF-ERCC1 endonuclease activity. In contrast, aRPA exhibits higher affinity for damaged DNA than canonical RPA, which may explain its ability to substitute for RPA in the excision step of nucleotide excision repair. Our findings provide the first direct evidence for the function of aRPA in human DNA metabolism and support a model for aRPA functioning in chromosome maintenance functions in nonproliferating cells.
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Affiliation(s)
- Michael G Kemp
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
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42
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Haring SJ, Humphreys TD, Wold MS. A naturally occurring human RPA subunit homolog does not support DNA replication or cell-cycle progression. Nucleic Acids Res 2009; 38:846-58. [PMID: 19942684 PMCID: PMC2817474 DOI: 10.1093/nar/gkp1062] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Replication Protein A (RPA) is a single-stranded DNA-binding protein essential for DNA replication, repair, recombination and cell-cycle regulation. A human homolog of the RPA2 subunit, called RPA4, was previously identified and shown to be expressed in colon mucosal and placental cells; however, the function of RPA4 was not determined. To examine the function of RPA4 in human cells, we carried out knockdown and replacement studies to determine whether RPA4 can substitute for RPA2 in the cell. Unlike RPA2, exogenous RPA4 expression did not support chromosomal DNA replication and lead to cell-cycle arrest in G2/M. In addition, RPA4 localized to sites of DNA repair and reduced γ-H2AX caused by RPA2 depletion. These studies suggest that RPA4 cannot support cell proliferation but can support processes that maintain the genomic integrity of the cell.
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Affiliation(s)
- Stuart J Haring
- Department of Biochemistry, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA
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43
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Dragnea V, Arunkumar AI, Yuan H, Giedroc DP, Bauer CE. Spectroscopic studies of the AppA BLUF domain from Rhodobacter sphaeroides: addressing movement of tryptophan 104 in the signaling state. Biochemistry 2009; 48:9969-79. [PMID: 19746968 DOI: 10.1021/bi9009067] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previous crystallographic studies of the AppA BLUF domain indicated that Trp104 is capable of undertaking alternate conformations depending on the length of the BLUF domain. A BLUF domain containing a C-terminal deletion (AppA1-126) reveals that Trp104 is partially solvent exposed while a BLUF domain containing a slightly longer carboxyl terminal region (AppA17-133) shows that Trp104 is deeply buried. This observation has led to a model proposing that Trp104 moves from a deeply buried position in the dark state to a solvent-exposed position in the light excited state. In this study we investigated whether there is indeed movement of Trp104 upon light excitation using a combination of NMR and absorption spectroscopy, steady-state fluorescence, and acrylamide quenching of tryptophan fluorescence. Our results indicate that AppA17-133 and AppA1-126 contain Trp104 in distinct alternate conformations in solution and that light absorption by the flavin causes partial movement/uncovering of Trp104. However, we conclude that light exposure does not cause dramatic change of Trp104 from "Trp-in" to "Trp-out" conformations (or vice versa) upon light absorption. These results do not support a model of Trp104 movement as a key output signal.
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Affiliation(s)
- Vladimira Dragnea
- Departments of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA
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44
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Nuss JE, Sweeney DJ, Alter GM. Prediction of and experimental support for the three-dimensional structure of replication protein A. Biochemistry 2009; 48:7892-905. [PMID: 19621872 DOI: 10.1021/bi801896s] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Replication protein A (RPA) is a heterotrimeric, multidomain, single-stranded DNA binding protein that is essential for DNA replication, repair, and recombination. Crystallographic and NMR studies on RPA protein fragments have provided structures for all domains; however, intact heterotrimeric RPA has resisted crystallization, and a complete protein structure has not yet been described. In this study, computational methods and experimental reactivity information (MRAN) were used to model the complete structure of RPA. To accomplish this, models of RPA's globular domains and its domain-linking regions were docked in various orders. We also determined rates of proteolytic cleavage and amino acid side chain chemical modifications in native, solution state RPA. These experimental data were used to select alternate modeling intermediates and final structural models, leading to a single model most consistent with our results. Using molecular dynamics simulations and multiple rounds of simulated annealing, we then relaxed this structural model and examined its flexibility. The family of resultant models is consistent with other, previously published, critical lines of evidence and with experimental reactivity data presented herein.
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Affiliation(s)
- Jonathan Eric Nuss
- Department of Biochemistry and Molecular Biology and Biomedical Sciences Ph.D. Program, Wright State University, Dayton, Ohio 45435, USA
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45
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Janowski R, Panjikar S, Eddine AN, Kaufmann SHE, Weiss MS. Structural analysis reveals DNA binding properties of Rv2827c, a hypothetical protein from Mycobacterium tuberculosis. JOURNAL OF STRUCTURAL AND FUNCTIONAL GENOMICS 2009; 10:137-50. [PMID: 19184528 PMCID: PMC2758359 DOI: 10.1007/s10969-009-9060-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 01/14/2009] [Indexed: 01/07/2023]
Abstract
Tuberculosis (TB) is a major global health threat caused by Mycobacterium tuberculosis (Mtb). It is further fueled by the HIV pandemic and by increasing incidences of multidrug resistant Mtb-strains. Rv2827c, a hypothetical protein from Mtb, has been implicated in the survival of Mtb in the macrophages of the host. The three-dimensional structure of Rv2827c has been determined by the three-wavelength anomalous diffraction technique using bromide-derivatized crystals and refined to a resolution of 1.93 A. The asymmetric unit of the orthorhombic crystals contains two independent protein molecules related by a non-crystallographic translation. The tertiary structure of Rv2827c comprises two domains: an N-terminal domain displaying a winged helix topology and a C-terminal domain, which appears to constitute a new and unique fold. Based on structural homology considerations and additional biochemical evidence, it could be established that Rv2827c is a DNA-binding protein. Once the understanding of the structure-function relationship of Rv2827c extends to the function of Rv2827c in vivo, new clues for the rational design of novel intervention strategies may be obtained.
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Affiliation(s)
- Robert Janowski
- EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, 22603, Hamburg, Germany ,IBMB (CSIC), Parc Científic de Barcelona, Baldiri Riexac 10–12, 08028 Barcelona, Spain
| | - Santosh Panjikar
- EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, 22603, Hamburg, Germany
| | - Ali Nasser Eddine
- Max Planck Institute for Infection Biology, Charitéplatz 1, 10117, Berlin, Germany
| | | | - Manfred S. Weiss
- EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, 22603, Hamburg, Germany
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Wright CM, Seguin SP, Fewell SW, Zhang H, Ishwad C, Vats A, Lingwood CA, Wipf P, Fanning E, Pipas JM, Brodsky JL. Inhibition of Simian Virus 40 replication by targeting the molecular chaperone function and ATPase activity of T antigen. Virus Res 2009; 141:71-80. [PMID: 19200446 DOI: 10.1016/j.virusres.2008.12.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 12/29/2008] [Accepted: 12/29/2008] [Indexed: 01/23/2023]
Abstract
Polyomaviruses such as BK virus and JC virus have been linked to several diseases, but treatments that thwart their propagation are limited in part because of slow growth and cumbersome culturing conditions. In contrast, the replication of one member of this family, Simian Virus 40 (SV40), is robust and has been well-characterized. SV40 replication requires two domains within the viral-encoded large tumor antigen (TAg): The ATPase domain and the N-terminal J domain, which stimulates the ATPase activity of the Hsp70 chaperone. To assess whether inhibitors of polyomavirus replication could be identified, we examined a recently described library of small molecules, some of which inhibit chaperone function. One compound, MAL2-11B, inhibited both TAg's endogenous ATPase activity and the TAg-mediated activation of Hsp70. MAL2-11B also reduced SV40 propagation in plaque assays and compromised DNA replication in cell culture and in vitro. Furthermore, the compound significantly reduced the growth of BK virus in a human kidney cell line. These data indicate that pharmacological inhibition of TAg's chaperone and ATPase activities may provide a route to combat polyomavirus-mediated disease.
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Affiliation(s)
- Christine M Wright
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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Mason AC, Haring SJ, Pryor JM, Staloch CA, Gan TF, Wold MS. An alternative form of replication protein a prevents viral replication in vitro. J Biol Chem 2008; 284:5324-31. [PMID: 19116208 DOI: 10.1074/jbc.m808963200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Replication protein A (RPA), the eukaryotic single-stranded DNA-binding complex, is essential for multiple processes in cellular DNA metabolism. The "canonical" RPA is composed of three subunits (RPA1, RPA2, and RPA3); however, there is a human homolog to the RPA2 subunit, called RPA4, that can substitute for RPA2 in complex formation. We demonstrate that the resulting "alternative" RPA (aRPA) complex has solution and DNA binding properties indistinguishable from the canonical RPA complex; however, aRPA is unable to support DNA replication and inhibits canonical RPA function. Two regions of RPA4, the putative L34 loop and the C terminus, are responsible for inhibiting SV40 DNA replication. Given that aRPA inhibits canonical RPA function in vitro and is found in nonproliferative tissues, these studies indicate that RPA4 expression may prevent cellular proliferation via replication inhibition while playing a role in maintaining the viability of quiescent cells.
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Affiliation(s)
- Aaron C Mason
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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48
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Fanning E, Zhao K. SV40 DNA replication: from the A gene to a nanomachine. Virology 2008; 384:352-9. [PMID: 19101707 DOI: 10.1016/j.virol.2008.11.038] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 11/18/2008] [Indexed: 12/23/2022]
Abstract
Duplication of the simian virus 40 (SV40) genome is the best understood eukaryotic DNA replication process to date. Like most prokaryotic genomes, the SV40 genome is a circular duplex DNA organized in a single replicon. This small viral genome, its association with host histones in nucleosomes, and its dependence on the host cell milieu for replication factors and precursors led to its adoption as a simple and powerful model. The steps in replication, the viral initiator, the host proteins, and their mechanisms of action were initially defined using a cell-free SV40 replication reaction. Although our understanding of the vastly more complex host replication fork is advancing, no eukaryotic replisome has yet been reconstituted and the SV40 paradigm remains a point of reference. This article reviews some of the milestones in the development of this paradigm and speculates on its potential utility to address unsolved questions in eukaryotic genome maintenance.
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Affiliation(s)
- Ellen Fanning
- Department of Biological Sciences, Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN 37235-1634, USA.
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Validation of BKV large T-antigen ATP-binding site as a target for drug discovery. Antiviral Res 2008; 81:184-7. [PMID: 19084558 DOI: 10.1016/j.antiviral.2008.11.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Revised: 11/08/2008] [Accepted: 11/11/2008] [Indexed: 11/21/2022]
Abstract
BK virus large T antigen (LTA) is a hexameric protein with a helicase activity that is powered by ATP hydrolysis. A mutant virus with Lys420Ala, Arg421Ala, and Asp504Ala mutations at the ATP binding sites showed marked reduction in viral fitness. This observation indicates that high throughput screening for ATPase inhibitors will be valid strategy to discover anti-BKV drugs. Pilot screening of 300 compounds from the Tim Tec ActiTarg K library identified a compound, STO18584, with selectivity index of 19.2.
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Salas TR, Petruseva I, Lavrik O, Saintomé C. Evidence for direct contact between the RPA3 subunit of the human replication protein A and single-stranded DNA. Nucleic Acids Res 2008; 37:38-46. [PMID: 19010961 PMCID: PMC2615627 DOI: 10.1093/nar/gkn895] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Replication Protein A is a single-stranded (ss) DNA-binding protein that is highly conserved in eukaryotes and plays essential roles in many aspects of nucleic acid metabolism, including replication, recombination, DNA repair and telomere maintenance. It is a heterotrimeric complex consisting of three subunits: RPA1, RPA2 and RPA3. It possesses four DNA-binding domains (DBD), DBD-A, DBD-B and DBD-C in RPA1 and DBD-D in RPA2, and it binds ssDNA via a multistep pathway. Unlike the RPA1 and RPA2 subunits, no ssDNA-RPA3 interaction has as yet been observed although RPA3 contains a structural motif found in the other DBDs. We show here using 4-thiothymine residues as photoaffinity probe that RPA3 interacts directly with ssDNA on the 3'-side on a 31 nt ssDNA.
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Affiliation(s)
- Tonatiuh Romero Salas
- Laboratoire de Biophysique Moléculaire, Cellulaire et Tissulaire, CNRS-ParisVI-Paris XIII-UMR 7033, Paris, France
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