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Wu RA, Pellman DS, Walter JC. The Ubiquitin Ligase TRAIP: Double-Edged Sword at the Replisome. Trends Cell Biol 2021; 31:75-85. [PMID: 33317933 PMCID: PMC7856240 DOI: 10.1016/j.tcb.2020.11.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 11/09/2020] [Accepted: 11/16/2020] [Indexed: 12/12/2022]
Abstract
In preparation for cell division, the genome must be copied with high fidelity. However, replisomes often encounter obstacles, including bulky DNA lesions caused by reactive metabolites and chemotherapeutics, as well as stable nucleoprotein complexes. Here, we discuss recent advances in our understanding of TRAIP, a replisome-associated E3 ubiquitin ligase that is mutated in microcephalic primordial dwarfism. In interphase, TRAIP helps replisomes overcome DNA interstrand crosslinks and DNA-protein crosslinks, whereas in mitosis it triggers disassembly of all replisomes that remain on chromatin. We describe a model to explain how TRAIP performs these disparate functions and how they help maintain genome integrity.
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Affiliation(s)
- R Alex Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - David S Pellman
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA; Howard Hughes Medical Institute, Cambridge, MA, 02139, USA
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA; Howard Hughes Medical Institute, Cambridge, MA, 02139, USA.
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2
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Vrtis KB, Dewar JM, Chistol G, Wu RA, Graham TGW, Walter JC. Single-strand DNA breaks cause replisome disassembly. Mol Cell 2021; 81:1309-1318.e6. [PMID: 33484638 DOI: 10.1016/j.molcel.2020.12.039] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 12/11/2020] [Accepted: 12/23/2020] [Indexed: 11/16/2022]
Abstract
DNA damage impedes replication fork progression and threatens genome stability. Upon encounter with most DNA adducts, the replicative CMG helicase (CDC45-MCM2-7-GINS) stalls or uncouples from the point of synthesis, yet eventually resumes replication. However, little is known about the effect on replication of single-strand breaks or "nicks," which are abundant in mammalian cells. Using Xenopus egg extracts, we reveal that CMG collision with a nick in the leading strand template generates a blunt-ended double-strand break (DSB). Moreover, CMG, which encircles the leading strand template, "runs off" the end of the DSB. In contrast, CMG collision with a lagging strand nick generates a broken end with a single-stranded overhang. In this setting, CMG translocates along double-stranded DNA beyond the break and is then ubiquitylated and removed from chromatin by the same pathway used during replication termination. Our results show that nicks are uniquely dangerous DNA lesions that invariably cause replisome disassembly, and they suggest that CMG cannot be stored on dsDNA while cells resolve replication stress.
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Affiliation(s)
- Kyle B Vrtis
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - James M Dewar
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - Gheorghe Chistol
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - R Alex Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - Thomas G W Graham
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA.
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3
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Wang AS, Chen LC, Wu RA, Hao Y, McSwiggen DT, Heckert AB, Richardson CD, Gowen BG, Kazane KR, Vu JT, Wyman SK, Shin JJ, Darzacq X, Walter JC, Corn JE. The Histone Chaperone FACT Induces Cas9 Multi-turnover Behavior and Modifies Genome Manipulation in Human Cells. Mol Cell 2020; 79:221-233.e5. [PMID: 32603710 PMCID: PMC7398558 DOI: 10.1016/j.molcel.2020.06.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 02/26/2020] [Accepted: 06/05/2020] [Indexed: 12/23/2022]
Abstract
Cas9 is a prokaryotic RNA-guided DNA endonuclease that binds substrates tightly in vitro but turns over rapidly when used to manipulate genomes in eukaryotic cells. Little is known about the factors responsible for dislodging Cas9 or how they influence genome engineering. Unbiased detection through proximity labeling of transient protein interactions in cell-free Xenopus laevis egg extract identified the dimeric histone chaperone facilitates chromatin transcription (FACT) as an interactor of substrate-bound Cas9. FACT is both necessary and sufficient to displace dCas9, and FACT immunodepletion converts Cas9's activity from multi-turnover to single turnover. In human cells, FACT depletion extends dCas9 residence times, delays genome editing, and alters the balance between indel formation and homology-directed repair. FACT knockdown also increases epigenetic marking by dCas9-based transcriptional effectors with a concomitant enhancement of transcriptional modulation. FACT thus shapes the intrinsic cellular response to Cas9-based genome manipulation most likely by determining Cas9 residence times.
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Affiliation(s)
- Alan S Wang
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Leo C Chen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - R Alex Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Yvonne Hao
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - David T McSwiggen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute of Regenerative Medicine Center of Excellence, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Alec B Heckert
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute of Regenerative Medicine Center of Excellence, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Christopher D Richardson
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Benjamin G Gowen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Katelynn R Kazane
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Jonathan T Vu
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Stacia K Wyman
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Jiyung J Shin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute of Regenerative Medicine Center of Excellence, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Jacob E Corn
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA 94720, USA; Department of Biology, ETH Zürich, 8093 Zürich, Switzerland.
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4
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Amunugama R, Willcox S, Wu RA, Abdullah UB, El-Sagheer AH, Brown T, McHugh PJ, Griffith JD, Walter JC. Replication Fork Reversal during DNA Interstrand Crosslink Repair Requires CMG Unloading. Cell Rep 2019; 23:3419-3428. [PMID: 29924986 PMCID: PMC6086610 DOI: 10.1016/j.celrep.2018.05.061] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 03/29/2018] [Accepted: 05/17/2018] [Indexed: 01/08/2023] Open
Abstract
DNA interstrand crosslinks (ICLs) are extremely cytotoxic, but the mechanism of their repair remains incompletely understood. Using Xenopus egg extracts, we previously showed that repair of a cisplatin ICL is triggered when two replication forks converge on the lesion. After CDC45/MCM2-7/GINS (CMG) ubiquitylation and unloading by the p97 segregase, FANCI-FANCD2 promotes DNA incisions by XPF-ERCC1, leading to ICL unhooking. Here, we report that, during this cell-free ICL repair reaction, one of the two converged forks undergoes reversal. Fork reversal fails when CMG unloading is inhibited, but it does not require FANCI-FANCD2. After one fork has undergone reversal, the opposing fork that still abuts the ICL undergoes incisions. Our data show that replication fork reversal at an ICL requires replisome disassembly. We present a revised model of ICL repair that involves a reversed fork intermediate.
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Affiliation(s)
- Ravindra Amunugama
- Howard Hughes Medical Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Smaranda Willcox
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA
| | - R Alex Wu
- Howard Hughes Medical Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Ummi B Abdullah
- Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | | | - Tom Brown
- Department of Chemistry, University of Oxford, Oxford OX1 3TA, UK; Department of Oncology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK
| | - Peter J McHugh
- Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Johannes C Walter
- Howard Hughes Medical Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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Deng L, Wu RA, Sonneville R, Kochenova OV, Labib K, Pellman D, Walter JC. Mitotic CDK Promotes Replisome Disassembly, Fork Breakage, and Complex DNA Rearrangements. Mol Cell 2019; 73:915-929.e6. [PMID: 30849395 PMCID: PMC6410736 DOI: 10.1016/j.molcel.2018.12.021] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 10/03/2018] [Accepted: 12/21/2018] [Indexed: 12/27/2022]
Abstract
DNA replication errors generate complex chromosomal rearrangements and thereby contribute to tumorigenesis and other human diseases. One mechanism that triggers these errors is mitotic entry before the completion of DNA replication. To address how mitosis might affect DNA replication, we used Xenopus egg extracts. When mitotic CDK (Cyclin B1-CDK1) is used to drive interphase egg extracts into a mitotic state, the replicative CMG (CDC45/MCM2-7/GINS) helicase undergoes ubiquitylation on its MCM7 subunit, dependent on the E3 ubiquitin ligase TRAIP. Whether replisomes have stalled or undergone termination, CMG ubiquitylation is followed by its extraction from chromatin by the CDC48/p97 ATPase. TRAIP-dependent CMG unloading during mitosis is also seen in C. elegans early embryos. At stalled forks, CMG removal results in fork breakage and end joining events involving deletions and templated insertions. Our results identify a mitotic pathway of global replisome disassembly that can trigger replication fork collapse and DNA rearrangements.
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Affiliation(s)
- Lin Deng
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - R Alex Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - Remi Sonneville
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Olga V Kochenova
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA
| | - Karim Labib
- MRC Protein Phosphorylation and Ubiquitylation Unit, Sir James Black Centre, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - David Pellman
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA; Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA.
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Blavatnik Institute, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA.
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6
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Wu RA, Semlow DR, Kamimae-Lanning AN, Kochenova OV, Chistol G, Hodskinson MR, Amunugama R, Sparks JL, Wang M, Deng L, Mimoso CA, Low E, Patel KJ, Walter JC. TRAIP is a master regulator of DNA interstrand crosslink repair. Nature 2019; 567:267-272. [PMID: 30842657 PMCID: PMC6417926 DOI: 10.1038/s41586-019-1002-0] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 02/01/2019] [Indexed: 12/24/2022]
Abstract
Cells often use multiple pathways to repair the same DNA lesion, and the choice of pathway has substantial implications for the fidelity of genome maintenance. DNA interstrand crosslinks covalently link the two strands of DNA, and thereby block replication and transcription; the cytotoxicity of these crosslinks is exploited for chemotherapy. In Xenopus egg extracts, the collision of replication forks with interstrand crosslinks initiates two distinct repair pathways. NEIL3 glycosylase can cleave the crosslink1; however, if this fails, Fanconi anaemia proteins incise the phosphodiester backbone that surrounds the interstrand crosslink, generating a double-strand-break intermediate that is repaired by homologous recombination2. It is not known how the simpler NEIL3 pathway is prioritized over the Fanconi anaemia pathway, which can cause genomic rearrangements. Here we show that the E3 ubiquitin ligase TRAIP is required for both pathways. When two replisomes converge at an interstrand crosslink, TRAIP ubiquitylates the replicative DNA helicase CMG (the complex of CDC45, MCM2-7 and GINS). Short ubiquitin chains recruit NEIL3 through direct binding, whereas longer chains are required for the unloading of CMG by the p97 ATPase, which enables the Fanconi anaemia pathway. Thus, TRAIP controls the choice between the two known pathways of replication-coupled interstrand-crosslink repair. These results, together with our other recent findings3,4 establish TRAIP as a master regulator of CMG unloading and the response of the replisome to obstacles.
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Affiliation(s)
- R Alex Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Daniel R Semlow
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | | | - Olga V Kochenova
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Gheorghe Chistol
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | | | - Ravindra Amunugama
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Justin L Sparks
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Meng Wang
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
- Department of Haematology, University of Cambridge, Cambridge, UK
| | - Lin Deng
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Claudia A Mimoso
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Emily Low
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Ketan J Patel
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA.
- Howard Hughes Medical Institute, Boston, MA, USA.
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7
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Larsen NB, Gao AO, Sparks JL, Gallina I, Wu RA, Mann M, Räschle M, Walter JC, Duxin JP. Replication-Coupled DNA-Protein Crosslink Repair by SPRTN and the Proteasome in Xenopus Egg Extracts. Mol Cell 2018; 73:574-588.e7. [PMID: 30595436 PMCID: PMC6375733 DOI: 10.1016/j.molcel.2018.11.024] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 09/20/2018] [Accepted: 11/15/2018] [Indexed: 01/19/2023]
Abstract
DNA-protein crosslinks (DPCs) are bulky lesions that interfere with DNA metabolism and therefore threaten genomic integrity. Recent studies implicate the metalloprotease SPRTN in S phase removal of DPCs, but how SPRTN is targeted to DPCs during DNA replication is unknown. Using Xenopus egg extracts that recapitulate replication-coupled DPC proteolysis, we show that DPCs can be degraded by SPRTN or the proteasome, which act as independent DPC proteases. Proteasome recruitment requires DPC polyubiquitylation, which is partially dependent on the ubiquitin ligase activity of TRAIP. In contrast, SPRTN-mediated DPC degradation does not require DPC polyubiquitylation but instead depends on nascent strand extension to within a few nucleotides of the lesion, implying that polymerase stalling at the DPC activates SPRTN on both leading and lagging strand templates. Our results demonstrate that SPRTN and proteasome activities are coupled to DNA replication by distinct mechanisms that promote replication across immovable protein barriers.
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Affiliation(s)
- Nicolai B Larsen
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Alan O Gao
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, DK-2200 Copenhagen, Denmark; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Justin L Sparks
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Irene Gallina
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - R Alex Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Matthias Mann
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, DK-2200 Copenhagen, Denmark; Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Markus Räschle
- Department of Molecular Biotechnology and Systems Biology, Technical University of Kaiserslautern, 67653 Kaiserslautern, Germany
| | - Johannes C Walter
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
| | - Julien P Duxin
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, DK-2200 Copenhagen, Denmark.
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Abstract
Telomerase is the essential reverse transcriptase required for linear chromosome maintenance in most eukaryotes. Telomerase supplements the tandem array of simple-sequence repeats at chromosome ends to compensate for the DNA erosion inherent in genome replication. The template for telomerase reverse transcriptase is within the RNA subunit of the ribonucleoprotein complex, which in cells contains additional telomerase holoenzyme proteins that assemble the active ribonucleoprotein and promote its function at telomeres. Telomerase is distinct among polymerases in its reiterative reuse of an internal template. The template is precisely defined, processively copied, and regenerated by release of single-stranded product DNA. New specificities of nucleic acid handling that underlie the catalytic cycle of repeat synthesis derive from both active site specialization and new motif elaborations in protein and RNA subunits. Studies of telomerase provide unique insights into cellular requirements for genome stability, tissue renewal, and tumorigenesis as well as new perspectives on dynamic ribonucleoprotein machines.
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Affiliation(s)
- R Alex Wu
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202; , , ,
| | - Heather E Upton
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202; , , ,
| | - Jacob M Vogan
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202; , , ,
| | - Kathleen Collins
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202; , , ,
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9
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Ye ML, Zou HF, Lei ZD, Wu RA, Ni JY. [Chiral separation by capillary electrochromatography on stationary phase adsorbed with protein]. Se Pu 2001; 19:390-4. [PMID: 12545430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023] Open
Abstract
A method based on the adsorption of bovine serum albumin (BSA) on the strong anion-exchange packing (SAX) was applied to prepare chiral stationary phases for capillary electrochromatography. It was found that the electroosmotic mobility only decreased 26.3% when the BSA was adsorbed. The run-to-run reproducibilities of void time and the migration times of D- and L-tryptophan enantiomers were rather good with the relative standard deviation (RSD) values of 0.90%, 0.87% and 0.96%, respectively, when mobile phase containing 7% (volume fraction) acetonitrile. The merit of this system is that the direction of electroosmotic flow is still from cathode to anode, preferable to separate acidic enantiomers. Four anionic enantiomers, tryptophan, ketoprofen, fenoprofen and warfarin, as well as the neutral enantiomers of benzoin were successfully resolved. In order to reduce the analysis time, n-hexanoic acid was added to the mobile phase as a competitive agent. The effect of acetonitrile volume fraction on the resolution of enantiomers was also investigated.
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Affiliation(s)
- M L Ye
- National Chromatographic R. & A. Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116011, China
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10
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Wu RA, Zou HF, Ye ML, Xiong BH, Ni JY. [Uncharged monolithic capillary column modified with an anionic surfactant in electrochromatography]. Se Pu 2001; 19:193-5. [PMID: 12541793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023] Open
Abstract
A monolithic capillary column was obtained by in-situ co-polymerization of butyl methacrylate with ethylene dimethacrylate. A mode of capillary electrochromatography (CEC) based on the dynamic adsorption of long chain sodium dodecyl sulfate(SDS) on the monolithic stationary phases was developed. Effects of SDS concentration and concentration of acetonitrile in mobile phase on the electroosmotic flow(EOF) of the column and the plate height on the electroosmotic velocity were investigated. Efficiency of monolithic capillary column with higher than 140,000 plates per meter for neutral aromatic compounds were obtained, and the relative standard deviations observed for dead time(t0) and retention times of neutral solutes were about 0.22% and less than 0.56% for ten consecutive runs, respectively.
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Affiliation(s)
- R A Wu
- School of Chemical and Environmental Engineering, Wenzhou University, Wenzhou 325027, China
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11
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Brinton TJ, Kailasam MT, Wu RA, Cervenka JH, Chio SS, Parmer RJ, DeMaria AN, O'Connor DT. Arterial compliance by cuff sphygmomanometer. Application to hypertension and early changes in subjects at genetic risk. Hypertension 1996; 28:599-603. [PMID: 8843884 DOI: 10.1161/01.hyp.28.4.599] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Abnormalities of the arterial pulse waveform reflect changes in cardiovascular structure and function. These abnormalities may occur early in the course of essential hypertension, even before the onset of blood pressure elevation. Previous studies of cardiovascular structure and function have relied on invasive intra-arterial cannulation to obtain the arterial pulse wave. We evaluated arterial structure and function using a noninvasive cuff sphygmomanometer in hypertensive (n = 15) and normotensive (n = 36) subjects stratified by genetic risk (family history) for hypertension. Using a simple physical model in which the aorta was assumed to be a T tube and the brachial artery a straight tube, we determined vascular compliance and peripheral resistance by analyzing the brachial artery pulsation signal from a cuff sphygmomanometer. Essential hypertensive subjects tended to have higher peripheral resistance (P = .06) and significantly lower vascular compliance (P = .001) than normotensive subjects. Vascular compliance correlated with simultaneously determined pulse pressure in both groups (n = 51, r = .74, P < .0001). Higher peripheral resistance (P = .07) and lower vascular compliance (P = .04) were already found in still-normotensive offspring of hypertensive parents (ie, normotensive subjects with a positive family history of hypertension) than in normotensive subjects with a negative family history of hypertension. Multivariate analysis demonstrated that both genetic risk for hypertension (P = .030) and blood pressure status (P = .041), although not age (P = .207), were significant predictors of vascular compliance (multiple R = .47, P = .011). However, by two-way ANOVA, genetic risk for hypertension was an even more significant determinant (F = 7.84, P = .007) of compliance than blood pressure status (F = 2.69, P = .089). Antihypertensive therapy with angiotensin-converting enzyme inhibitors (10 days, n = 10) improved vascular compliance (P = .02) and reduced resistance (P = .003) significantly; treatment with calcium channel antagonists (4 weeks, n = 8) tended to improve vascular compliance (P = .07) and significantly reduced peripheral resistance (P = .006). We conclude that arterial vascular compliance abnormalities detected by a noninvasive cuff sphygmomanometer reflect treatment-reversible changes in vascular structure and function. Early changes in vascular compliance in still-normotensive individuals at genetic risk for hypertension may be a heritable pathogenetic feature of this disorder.
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Affiliation(s)
- T J Brinton
- Department of Medicine, University of California-San Diego 92161, USA
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Kailasam MT, Parmer RJ, Cervenka JH, Wu RA, Ziegler MG, Kennedy BP, Adegbile IA, O'Connor DT. Divergent effects of dihydropyridine and phenylalkylamine calcium channel antagonist classes on autonomic function in human hypertension. Hypertension 1995; 26:143-9. [PMID: 7607717 DOI: 10.1161/01.hyp.26.1.143] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Calcium channel antagonists differ by class in reported frequency of side effects that suggest reflex sympathoadrenal activation. Do such differences result from differential effects on autonomic and baroreflex function? The present study compared acute and chronic effects of two classes of calcium channel antagonists, the dihydropyridine type (felodipine) and the phenylalkylamine type (verapamil), on efferent sympathetic outflow and baroreflex slope in 15 essential hypertensive subjects. Blood pressure, heart rate, hemodynamics, and biochemistries were determined at baseline and after acute (first dose) and chronic (4 weeks) administration of the drugs versus placebo. Acutely, felodipine caused a greater decrease in blood pressure associated with a larger decline in systemic vascular resistance than the corresponding effects produced by verapamil. Chronically, there were similar, significant declines in blood pressure (P = .001) and systemic vascular resistance (P = .001) after each drug. Acutely, increased sympathetic activity after felodipine was suggested by reflex tachycardia (from 69 +/- 3 to 74 +/- 2 beats per minute, P = .014) and elevation of plasma norepinephrine (from 264 +/- 25 to 323 +/- 25 pg/mL, P = .037), whereas after verapamil the corresponding changes were closely similar to those after placebo.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M T Kailasam
- Department of Medicine, University of California, San Diego 92161, USA
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Wu RA, Kailasam MT, Cervenka JH, Parmer RJ, Kennedy BP, Ziegler MG, O'Connor DT. Does lipophilicity of angiotensin converting enzyme inhibitors selectively influence autonomic neural function in human hypertension? J Hypertens 1994; 12:1243-7. [PMID: 7868871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
INTRODUCTION Angiotensin II has both central nervous system and peripheral effects on autonomic function. Ramipril is among the more lipophilic angiotensin converting enzyme (ACE) inhibitors, and hence can penetrate the central nervous system readily. METHODS We investigated whether rampiril has selective effects on autonomic control of the circulation in human hypertension, compared with the more hydrophilic ACE inhibitor enalapril. Blood pressure, hemodynamics and measurements of autonomic function were obtained in 13 essential hypertensive subjects after 10 days on placebo, and after crossover monotherapy with 10 days on enalapril versus 10 days on ramipril. RESULTS Both enalapril and ramipril lowered systolic, diastolic and mean arterial blood pressures significantly, with no reflex increase in heart rate. Plasma renin activity increased substantially on each of the ACE inhibitors. There were no significant effects of either agent on plasma catecholamines (norepinephrine or epinephrine) or chromogranin A, biochemical indices of efferent sympatho-adrenal outflow. There were also no significant changes after either agent in baroreflex sensitivity (to high- and low-pressure stimuli), the response to cold stress or sympathetic (alpha-adrenergic) participation in blood pressure maintenance. There was a marginal effect of ACE inhibition on alpha 1-adrenergic pressor sensitivity, but the two compounds did not differ significantly in this respect. CONCLUSION Autonomic control of circulatory function was maintained well after either lipophilic (ramipril) or hydrophilic (enalapril) ACE inhibitors, and the lipophilic compound ramipril had no additional effects on autonomic function beyond those shown by the hydrophilic agent enalapril.
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Affiliation(s)
- R A Wu
- Department of Medicine, University of California, San Diego 92161
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