1
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Yang KB, Cameranesi M, Gowder M, Martinez C, Shamovsky Y, Epshtein V, Hao Z, Nguyen T, Nirenstein E, Shamovsky I, Rasouly A, Nudler E. High-resolution landscape of an antibiotic binding site. Nature 2023; 622:180-187. [PMID: 37648864 PMCID: PMC10550828 DOI: 10.1038/s41586-023-06495-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 07/28/2023] [Indexed: 09/01/2023]
Abstract
Antibiotic binding sites are located in important domains of essential enzymes and have been extensively studied in the context of resistance mutations; however, their study is limited by positive selection. Using multiplex genome engineering1 to overcome this constraint, we generate and characterize a collection of 760 single-residue mutants encompassing the entire rifampicin binding site of Escherichia coli RNA polymerase (RNAP). By genetically mapping drug-enzyme interactions, we identify an alpha helix where mutations considerably enhance or disrupt rifampicin binding. We find mutations in this region that prolong antibiotic binding, converting rifampicin from a bacteriostatic to bactericidal drug by inducing lethal DNA breaks. The latter are replication dependent, indicating that rifampicin kills by causing detrimental transcription-replication conflicts at promoters. We also identify additional binding site mutations that greatly increase the speed of RNAP.Fast RNAP depletes the cell of nucleotides, alters cell sensitivity to different antibiotics and provides a cold growth advantage. Finally, by mapping natural rpoB sequence diversity, we discover that functional rifampicin binding site mutations that alter RNAP properties or confer drug resistance occur frequently in nature.
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Affiliation(s)
- Kevin B Yang
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Maria Cameranesi
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Manjunath Gowder
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Criseyda Martinez
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Yosef Shamovsky
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Vitaliy Epshtein
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Zhitai Hao
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Thao Nguyen
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Eric Nirenstein
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Ilya Shamovsky
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Aviram Rasouly
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, New York University School of Medicine, New York, NY, USA.
| | - Evgeny Nudler
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, New York University School of Medicine, New York, NY, USA.
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2
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de Siqueira GMV, Guazzaroni ME. Host-Dependent Improvement of GFP Expression in Pseudomonas putida KT2440 Using Terminators of Metagenomic Origin. ACS Synth Biol 2023; 12:1562-1566. [PMID: 37126733 DOI: 10.1021/acssynbio.3c00098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Transcriptional terminators are key players in the flow of genetic information, but are often overlooked in circuit design. In this work, we used the Standard European Vector Architecture (SEVA) as a scaffold to investigate the effects of different terminators in the output of a reporter construct expressed in two bacterial species, and found that replacing the conventional T1 and T0 transcriptional terminators of the SEVA vector format with a set of broad-host metagenomic terminators resulted in a significant improvement in the signal of a fluorescent device in Pseudomonas putida KT2440 but not in Escherichia coli DH10B. Our results suggest that replacing the default set of terminators present in the SEVA specification may be an useful strategy for fine-tuning circuit expression in P. putida, which can be leveraged for the development of new devices with improved performance in this microbial host.
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Affiliation(s)
| | - María-Eugenia Guazzaroni
- Department of Biology, Faculty of Philosophy, Sciences and Letters at Ribeirão Preto, University of São Paulo, Ribeirao Preto 14040-901, Brazil
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3
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Huang D, Johnson AE, Sim BS, Lo TW, Merrikh H, Wiggins PA. The in vivo measurement of replication fork velocity and pausing by lag-time analysis. Nat Commun 2023; 14:1762. [PMID: 36997519 PMCID: PMC10063678 DOI: 10.1038/s41467-023-37456-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 03/17/2023] [Indexed: 03/31/2023] Open
Abstract
AbstractAn important step towards understanding the mechanistic basis of the central dogma is the quantitative characterization of the dynamics of nucleic-acid-bound molecular motors in the context of the living cell. To capture these dynamics, we develop lag-time analysis, a method for measuring in vivo dynamics. Using this approach, we provide quantitative locus-specific measurements of fork velocity, in units of kilobases per second, as well as replisome pause durations, some with the precision of seconds. The measured fork velocity is observed to be both locus and time dependent, even in wild-type cells. In this work, we quantitatively characterize known phenomena, detect brief, locus-specific pauses at ribosomal DNA loci in wild-type cells, and observe temporal fork velocity oscillations in three highly-divergent bacterial species.
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4
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Mitogenome-wise codon usage pattern from comparative analysis of the first mitogenome of Blepharipa sp. (Muga uzifly) with other Oestroid flies. Sci Rep 2022; 12:7028. [PMID: 35487927 PMCID: PMC9054809 DOI: 10.1038/s41598-022-10547-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 03/21/2022] [Indexed: 11/08/2022] Open
Abstract
Uziflies (Family: Tachinidae) are dipteran endoparasites of sericigenous insects which cause major economic loss in the silk industry globally. Here, we are presenting the first full mitogenome of Blepharipa sp. (Acc: KY644698, 15,080 bp, A + T = 78.41%), a dipteran parasitoid of Muga silkworm (Antheraea assamensis) found in the Indian states of Assam and Meghalaya. This study has confirmed that Blepharipa sp. mitogenome gene content and arrangement is similar to other Tachinidae and Sarcophagidae flies of Oestroidea superfamily, typical of ancestral Diptera. Although, Calliphoridae and Oestridae flies have undergone tRNA translocation and insertion, forming unique intergenic spacers (IGS) and overlapping regions (OL) and a few of them (IGS, OL) have been conserved across Oestroidea flies. The Tachinidae mitogenomes exhibit more AT content and AT biased codons in their protein-coding genes (PCGs) than the Oestroidea counterpart. About 92.07% of all (3722) codons in PCGs of this new species have A/T in their 3rd codon position. The high proportion of AT and repeats in the control region (CR) affects sequence coverage, resulting in a short CR (Blepharipa sp.: 168 bp) and a smaller tachinid mitogenome. Our research unveils those genes with a high AT content had a reduced effective number of codons, leading to high codon usage bias. The neutrality test shows that natural selection has a stronger influence on codon usage bias than directed mutational pressure. This study also reveals that longer PCGs (e.g., nad5, cox1) have a higher codon usage bias than shorter PCGs (e.g., atp8, nad4l). The divergence rates increase nonlinearly as AT content at the 3rd codon position increases and higher rate of synonymous divergence than nonsynonymous divergence causes strong purifying selection. The phylogenetic analysis explains that Blepharipa sp. is well suited in the family of insectivorous tachinid maggots. It's possible that biased codon usage in the Tachinidae family reduces the effective number of codons, and purifying selection retains the core functions in their mitogenome, which could help with efficient metabolism in their endo-parasitic life style and survival strategy.
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5
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Tsirkas I, Dovrat D, Thangaraj M, Brouwer I, Cohen A, Paleiov Z, Meijler MM, Lenstra T, Aharoni A. Transcription-replication coordination revealed in single live cells. Nucleic Acids Res 2022; 50:2143-2156. [PMID: 35137218 PMCID: PMC8887460 DOI: 10.1093/nar/gkac069] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 01/04/2022] [Accepted: 01/25/2022] [Indexed: 11/23/2022] Open
Abstract
The coexistence of DNA replication and transcription during S-phase requires their tight coordination to prevent harmful conflicts. While extensive research revealed important mechanisms for minimizing these conflicts and their consequences, little is known regarding how the replication and transcription machinery are coordinated in real-time. Here, we developed a live-cell imaging approach for the real-time monitoring of replisome progression and transcription dynamics during a transcription-replication encounter. We found a wave of partial transcriptional repression ahead of the moving replication fork, which may contribute to efficient fork progression through the transcribed gene. Real-time detection of conflicts revealed their negative impact on both processes, leading to fork stalling or slowdown as well as lower transcription levels during gene replication, with different trade-offs observed in defined subpopulations of cells. Our real-time measurements of transcription-replication encounters demonstrate how these processes can proceed simultaneously while maintaining genomic stability, and how conflicts can arise when coordination is impaired.
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Affiliation(s)
- Ioannis Tsirkas
- Department of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel
| | - Daniel Dovrat
- Department of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel
| | - Manikandan Thangaraj
- The Department of Chemistry and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel
| | - Ineke Brouwer
- Division of Gene Regulation, The Netherlands Cancer Institute, Oncode Institute,1066CX Amsterdam, The Netherlands
| | - Amit Cohen
- Department of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel
| | - Zohar Paleiov
- Department of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel
| | - Michael M Meijler
- The Department of Chemistry and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel
| | - Tineke Lenstra
- Division of Gene Regulation, The Netherlands Cancer Institute, Oncode Institute,1066CX Amsterdam, The Netherlands
| | - Amir Aharoni
- Department of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel
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6
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The Role of Replication Clamp-Loader Protein HolC of Escherichia coli in Overcoming Replication/Transcription Conflicts. mBio 2021; 12:mBio.00184-21. [PMID: 33688004 PMCID: PMC8092217 DOI: 10.1128/mbio.00184-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Escherichia coli, DNA replication is catalyzed by an assembly of proteins, the DNA polymerase III holoenzyme. This complex includes the polymerase and proofreading subunits, the processivity clamp, and clamp loader complex. The holC gene encodes an accessory protein (known as χ) to the core clamp loader complex and is the only protein of the holoenzyme that binds to single-strand DNA binding protein, SSB. HolC is not essential for viability, although mutants show growth impairment, genetic instability, and sensitivity to DNA damaging agents. In this study, we isolate spontaneous suppressor mutants in a ΔholC strain and identify these by whole-genome sequencing. Some suppressors are alleles of RNA polymerase, suggesting that transcription is problematic for holC mutant strains, or alleles of sspA, encoding stringent starvation protein. Using a conditional holC plasmid, we examine factors affecting transcription elongation and termination for synergistic or suppressive effects on holC mutant phenotypes. Alleles of RpoA (α), RpoB (β), and RpoC (β') RNA polymerase holoenzyme can partially suppress loss of HolC. In contrast, mutations in transcription factors DksA and NusA enhanced the inviability of holC mutants. HolC mutants showed enhanced sensitivity to bicyclomycin, a specific inhibitor of Rho-dependent termination. Bicyclomycin also reverses suppression of holC by rpoA, rpoC, and sspA An inversion of the highly expressed rrnA operon exacerbates the growth defects of holC mutants. We propose that transcription complexes block replication in holC mutants and that Rho-dependent transcriptional termination and DksA function are particularly important to sustain viability and chromosome integrity.IMPORTANCE Transcription elongation complexes present an impediment to DNA replication. We provide evidence that one component of the replication clamp loader complex, HolC, of Escherichia coli is required to overcome these blocks. This genetic study of transcription factor effects on holC growth defects implicates Rho-dependent transcriptional termination and DksA function as critical. It also implicates, for the first time, a role of SspA, stringent starvation protein, in avoidance or tolerance of replication/replication conflicts. We speculate that HolC helps avoid or resolve collisions between replication and transcription complexes, which become toxic in HolC's absence.
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7
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Nagy-Staron A, Tomasek K, Caruso Carter C, Sonnleitner E, Kavčič B, Paixão T, Guet CC. Local genetic context shapes the function of a gene regulatory network. eLife 2021; 10:e65993. [PMID: 33683203 PMCID: PMC7968929 DOI: 10.7554/elife.65993] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 02/19/2021] [Indexed: 11/13/2022] Open
Abstract
Gene expression levels are influenced by multiple coexisting molecular mechanisms. Some of these interactions such as those of transcription factors and promoters have been studied extensively. However, predicting phenotypes of gene regulatory networks (GRNs) remains a major challenge. Here, we use a well-defined synthetic GRN to study in Escherichia coli how network phenotypes depend on local genetic context, i.e. the genetic neighborhood of a transcription factor and its relative position. We show that one GRN with fixed topology can display not only quantitatively but also qualitatively different phenotypes, depending solely on the local genetic context of its components. Transcriptional read-through is the main molecular mechanism that places one transcriptional unit (TU) within two separate regulons without the need for complex regulatory sequences. We propose that relative order of individual TUs, with its potential for combinatorial complexity, plays an important role in shaping phenotypes of GRNs.
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Affiliation(s)
- Anna Nagy-Staron
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | - Kathrin Tomasek
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | | | - Elisabeth Sonnleitner
- Department of MicrobiologyImmunobiology and Genetics, Max F. Perutz Laboratories, Center Of Molecular Biology, University of ViennaViennaAustria
| | - Bor Kavčič
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | - Tiago Paixão
- Institute of Science and Technology AustriaKlosterneuburgAustria
| | - Calin C Guet
- Institute of Science and Technology AustriaKlosterneuburgAustria
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8
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Dutertre M, Sfaxi R, Vagner S. Reciprocal Links between Pre-messenger RNA 3'-End Processing and Genome Stability. Trends Biochem Sci 2021; 46:579-594. [PMID: 33653631 DOI: 10.1016/j.tibs.2021.01.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/11/2021] [Accepted: 01/22/2021] [Indexed: 02/07/2023]
Abstract
The 3'-end processing of most pre-messenger RNAs (pre-mRNAs) involves RNA cleavage and polyadenylation and is coupled to transcription termination. In both yeast and human cells, pre-mRNA 3'-end cleavage is globally inhibited by DNA damage. Recently, further links between pre-mRNA 3'-end processing and the control of genome stability have been uncovered, as reviewed here. Upon DNA damage, various genes related to the DNA damage response (DDR) escape 3'-end processing inhibition or are regulated through alternative polyadenylation (APA). Conversely, various pre-mRNA 3'-end processing factors prevent genome instability and are found at sites of DNA damage. Finally, the reciprocal link between pre-mRNA 3'-end processing and genome stability control seems important because it is conserved in evolution and involved in disease development.
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Affiliation(s)
- Martin Dutertre
- Institut Curie, Université PSL, CNRS UMR3348, INSERM U1278, 91400 Orsay, France; Université Paris-Saclay, CNRS UMR3348, INSERM U1278, 91400 Orsay, France; Equipe Labellisée Ligue Nationale Contre le Cancer.
| | - Rym Sfaxi
- Institut Curie, Université PSL, CNRS UMR3348, INSERM U1278, 91400 Orsay, France; Université Paris-Saclay, CNRS UMR3348, INSERM U1278, 91400 Orsay, France; Equipe Labellisée Ligue Nationale Contre le Cancer
| | - Stéphan Vagner
- Institut Curie, Université PSL, CNRS UMR3348, INSERM U1278, 91400 Orsay, France; Université Paris-Saclay, CNRS UMR3348, INSERM U1278, 91400 Orsay, France; Equipe Labellisée Ligue Nationale Contre le Cancer.
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9
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Schroeder JW, Sankar TS, Wang JD, Simmons LA. The roles of replication-transcription conflict in mutagenesis and evolution of genome organization. PLoS Genet 2020; 16:e1008987. [PMID: 32853297 PMCID: PMC7451550 DOI: 10.1371/journal.pgen.1008987] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Replication-transcription conflicts promote mutagenesis and give rise to evolutionary signatures, with fundamental importance to genome stability ranging from bacteria to metastatic cancer cells. This review focuses on the interplay between replication-transcription conflicts and the evolution of gene directionality. In most bacteria, the majority of genes are encoded on the leading strand of replication such that their transcription is co-directional with the direction of DNA replication fork movement. This gene strand bias arises primarily due to negative selection against deleterious consequences of head-on replication-transcription conflict. However, many genes remain head-on. Can head-on orientation provide some benefit? We combine insights from both mechanistic and evolutionary studies, review published work, and analyze gene expression data to evaluate an emerging model that head-on genes are temporal targets for adaptive mutagenesis during stress. We highlight the alternative explanation that genes in the head-on orientation may simply be the result of genomic inversions and relaxed selection acting on nonessential genes. We seek to clarify how the mechanisms of replication-transcription conflict, in concert with other mutagenic mechanisms, balanced by natural selection, have shaped bacterial genome evolution.
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Affiliation(s)
- Jeremy W. Schroeder
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - T. Sabari Sankar
- School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, Kerala, India
| | - Jue D. Wang
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Lyle A. Simmons
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
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10
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Üstüntanır Dede AF, Arslanyolu M. Construction and dynamic characterization of a Tetrahymena thermophila macronuclear artificial chromosome. Gene 2020; 748:144697. [PMID: 32325092 DOI: 10.1016/j.gene.2020.144697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 04/15/2020] [Accepted: 04/17/2020] [Indexed: 11/18/2022]
Abstract
Artificial chromosomes were previously generated for use in bacteria, protists, yeast and human cells. A Tetrahymena thermophila artificial chromosome could serve as a versatile platform to study diverse aspects of Tetrahymena biology and beyond. Here, we placed a C3-type rDNA replication origin and telomere sequences from T. thermophila into a pNeo4 vector, producing the first T. thermophila macronuclear artificial chromosome (TtAC1). Circular or linear forms of TtAC1 can be stably transformed into both vegetative and conjugative T. thermophila cells. Linear TtAC1 was stably double in copy number under antibiotic selection, but its copy number was dropping without antibiotic selection pressure. Southern blot, Real-Time PCR and E. coli retransformation analyses together showed that TtAC1 vector did not integrate into the macronuclear genome, and was maintained as a linear or a circular chromosome in T. thermophila macronucleus under antibiotic selection. The use of TtAC1 for recombinant protein production was demonstrated by western blot analysis of a secreted 27 kDa TtsfGFP-12XHis protein. We present the first macronuclear artificial chromosome with species-specific chromosomal elements for use in T. thermophila studies and to aid broad recombinant biotechnology applications.
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Affiliation(s)
- Ayça Fulya Üstüntanır Dede
- Department of Biology, Institute of Graduate Programs, Eskisehir Technical University, Yunusemre Campus, Eskisehir 26470, Turkey
| | - Muhittin Arslanyolu
- Department of Biology, Faculty of Sciences, Eskisehir Technical University, Yunusemre Campus, Eskisehir 26470, Turkey.
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11
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Subramanian H, Gatenby RA. Evolutionary advantage of anti-parallel strand orientation of duplex DNA. Sci Rep 2020; 10:9883. [PMID: 32555277 PMCID: PMC7303137 DOI: 10.1038/s41598-020-66705-3] [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: 01/01/2020] [Accepted: 05/22/2020] [Indexed: 11/09/2022] Open
Abstract
DNA in all living systems shares common properties that are remarkably well suited to its function, suggesting refinement by evolution. However, DNA also shares some counter-intuitive properties which confer no obvious benefit, such as strand directionality and anti-parallel strand orientation, which together result in the complicated lagging strand replication. The evolutionary dynamics that led to these properties of DNA remain unknown but their universality suggests that they confer as yet unknown selective advantage to DNA. In this article, we identify an evolutionary advantage of anti-parallel strand orientation of duplex DNA, within a given set of plausible premises. The advantage stems from the increased rate of replication, achieved by dividing the DNA into predictable, independently and simultaneously replicating segments, as opposed to sequentially replicating the entire DNA, thereby parallelizing the replication process. We show that anti-parallel strand orientation is essential for such a replicative organization of DNA, given our premises, the most important of which is the assumption of the presence of sequence-dependent asymmetric cooperativity in DNA.
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Affiliation(s)
| | - Robert A Gatenby
- Integrated Mathematical Oncology Department, Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, 12902, USF Magnolia Dr, Tampa, Florida, USA
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12
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Transcription shapes DNA replication initiation and termination in human cells. Nat Struct Mol Biol 2018; 26:67-77. [PMID: 30598550 PMCID: PMC6320713 DOI: 10.1038/s41594-018-0171-0] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 11/19/2018] [Indexed: 12/21/2022]
Abstract
Although DNA replication is a fundamental aspect of biology, it is not known what determines where DNA replication starts and stops in the human genome. Here we directly identify and quantitatively compare sites of replication initiation and termination in untransformed human cells. We report that replication preferentially initiates at the transcription start site of genes occupied by high levels of RNA polymerase II, and terminates at their polyadenylation sites, thus ensuring global co-directionality of transcription and replication, particularly at gene 5’ ends. During replication stress, replication initiation is stimulated downstream of genes and termination is redistributed to gene bodies; this globally re-orients replication relative to transcription around gene 3’ ends. These data suggest that replication initiation and termination are coupled to transcription in human cells, and propose a model for the impact of replication stress on genome integrity.
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13
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Albero R, Enjuanes A, Demajo S, Castellano G, Pinyol M, García N, Capdevila C, Clot G, Suárez-Cisneros H, Shimada M, Karube K, López-Guerra M, Colomer D, Beà S, Martin-Subero JI, Campo E, Jares P. Cyclin D1 overexpression induces global transcriptional downregulation in lymphoid neoplasms. J Clin Invest 2018; 128:4132-4147. [PMID: 29990311 DOI: 10.1172/jci96520] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 06/28/2018] [Indexed: 01/05/2023] Open
Abstract
Cyclin D1 is an oncogene frequently overexpressed in human cancers that has a dual function as cell cycle and transcriptional regulator, although the latter is widely unexplored. Here, we investigated the transcriptional role of cyclin D1 in lymphoid tumor cells with cyclin D1 oncogenic overexpression. Cyclin D1 showed widespread binding to the promoters of most actively transcribed genes, and the promoter occupancy positively correlated with the transcriptional output of targeted genes. Despite this association, the overexpression of cyclin D1 in lymphoid cells led to a global transcriptional downmodulation that was proportional to cyclin D1 levels. This cyclin D1-dependent global transcriptional downregulation was associated with a reduced nascent transcription and an accumulation of promoter-proximal paused RNA polymerase II (Pol II) that colocalized with cyclin D1. Concordantly, cyclin D1 overexpression promoted an increase in the Poll II pausing index. This transcriptional impairment seems to be mediated by the interaction of cyclin D1 with the transcription machinery. In addition, cyclin D1 overexpression sensitized cells to transcription inhibitors, revealing a synthetic lethality interaction that was also observed in primary mantle cell lymphoma cases. This finding of global transcriptional dysregulation expands the known functions of oncogenic cyclin D1 and suggests the therapeutic potential of targeting the transcriptional machinery in cyclin D1-overexpressing tumors.
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Affiliation(s)
| | - Anna Enjuanes
- Genomics Unit, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain
| | | | | | - Magda Pinyol
- Genomics Unit, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain
| | | | | | | | - Helena Suárez-Cisneros
- Genomics Unit, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Barcelona, Spain
| | - Mariko Shimada
- Hematopathology Unit and Cell Biology, Graduate School of Medicine and Faculty of Medicine, University of the Ryukyus, Nishihara, Japan.,Haematopathology Unit, Department of Anatomic Pathology, Hospital Clínic, University of Barcelona, Barcelona, Spain
| | - Kennosuke Karube
- Hematopathology Unit and Cell Biology, Graduate School of Medicine and Faculty of Medicine, University of the Ryukyus, Nishihara, Japan.,Haematopathology Unit, Department of Anatomic Pathology, Hospital Clínic, University of Barcelona, Barcelona, Spain
| | - Mónica López-Guerra
- Lymphoid Neoplasm Program and.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain.,Haematopathology Unit, Department of Anatomic Pathology, Hospital Clínic, University of Barcelona, Barcelona, Spain
| | - Dolors Colomer
- Lymphoid Neoplasm Program and.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain.,Haematopathology Unit, Department of Anatomic Pathology, Hospital Clínic, University of Barcelona, Barcelona, Spain
| | - Sílvia Beà
- Lymphoid Neoplasm Program and.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain
| | - José Ignacio Martin-Subero
- Lymphoid Neoplasm Program and.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain
| | - Elías Campo
- Lymphoid Neoplasm Program and.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain.,Haematopathology Unit, Department of Anatomic Pathology, Hospital Clínic, University of Barcelona, Barcelona, Spain
| | - Pedro Jares
- Lymphoid Neoplasm Program and.,Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Barcelona, Spain.,Molecular Biology Core, Hospital Clinic of Barcelona, Barcelona, Spain.,Haematopathology Unit, Department of Anatomic Pathology, Hospital Clínic, University of Barcelona, Barcelona, Spain
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14
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Lang KS, Merrikh H. The Clash of Macromolecular Titans: Replication-Transcription Conflicts in Bacteria. Annu Rev Microbiol 2018; 72:71-88. [PMID: 29856930 DOI: 10.1146/annurev-micro-090817-062514] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Within the last decade, it has become clear that DNA replication and transcription are routinely in conflict with each other in growing cells. Much of the seminal work on this topic has been carried out in bacteria, specifically, Escherichia coli and Bacillus subtilis; therefore, studies of conflicts in these species deserve special attention. Collectively, the recent findings on conflicts have fundamentally changed the way we think about DNA replication in vivo. Furthermore, new insights on this topic have revealed that the conflicts between replication and transcription significantly influence many key parameters of cellular function, including genome organization, mutagenesis, and evolution of stress response and virulence genes. In this review, we discuss the consequences of replication-transcription conflicts on the life of bacteria and describe some key strategies cells use to resolve them. We put special emphasis on two critical aspects of these encounters: ( a) the consequences of conflicts on replisome stability and dynamics, and ( b) the resulting increase in spontaneous mutagenesis.
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Affiliation(s)
- Kevin S Lang
- Department of Microbiology, University of Washington, Seattle, Washington 98195, USA;
| | - Houra Merrikh
- Department of Microbiology, University of Washington, Seattle, Washington 98195, USA; .,Department of Genome Sciences, University of Washington, Seattle, Washington 98195-5061, USA
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15
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McGinty RJ, Puleo F, Aksenova AY, Hisey JA, Shishkin AA, Pearson EL, Wang ET, Housman DE, Moore C, Mirkin SM. A Defective mRNA Cleavage and Polyadenylation Complex Facilitates Expansions of Transcribed (GAA) n Repeats Associated with Friedreich's Ataxia. Cell Rep 2018; 20:2490-2500. [PMID: 28877480 DOI: 10.1016/j.celrep.2017.08.051] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 07/19/2017] [Accepted: 08/15/2017] [Indexed: 02/03/2023] Open
Abstract
Expansions of microsatellite repeats are responsible for numerous hereditary diseases in humans, including myotonic dystrophy and Friedreich's ataxia. Whereas the length of an expandable repeat is the main factor determining disease inheritance, recent data point to genomic trans modifiers that can impact the likelihood of expansions and disease progression. Detection of these modifiers may lead to understanding and treating repeat expansion diseases. Here, we describe a method for the rapid, genome-wide identification of trans modifiers for repeat expansion in a yeast experimental system. Using this method, we found that missense mutations in the endoribonuclease subunit (Ysh1) of the mRNA cleavage and polyadenylation complex dramatically increase the rate of (GAA)n repeat expansions but only when they are actively transcribed. These expansions correlate with slower transcription elongation caused by the ysh1 mutation. These results reveal an interplay between RNA processing and repeat-mediated genome instability, confirming the validity of our approach.
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Affiliation(s)
- Ryan J McGinty
- Department of Biology, Tufts University, Medford, MA 02421, USA
| | - Franco Puleo
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Anna Y Aksenova
- Department of Biology, Tufts University, Medford, MA 02421, USA; Laboratory of Amyloid Biology, St. Petersburg State University, St. Petersburg 199034, Russia
| | - Julia A Hisey
- Department of Biology, Tufts University, Medford, MA 02421, USA
| | - Alexander A Shishkin
- Department of Biology, Tufts University, Medford, MA 02421, USA; The Broad Institute of MIT and Harvard, Cambridge, MA 02139, USA
| | - Erika L Pearson
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Eric T Wang
- The David H. Koch Institute for Integrative Cancer Research at MIT, Cambridge, MA 02139, USA; Center for Neurogenetics, University of Florida, Gainesville, FL 32610, USA
| | - David E Housman
- The David H. Koch Institute for Integrative Cancer Research at MIT, Cambridge, MA 02139, USA
| | - Claire Moore
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, MA 02421, USA.
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16
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Schroeder JW, Yeesin P, Simmons LA, Wang JD. Sources of spontaneous mutagenesis in bacteria. Crit Rev Biochem Mol Biol 2017; 53:29-48. [PMID: 29108429 DOI: 10.1080/10409238.2017.1394262] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Mutations in an organism's genome can arise spontaneously, that is, in the absence of exogenous stress and prior to selection. Mutations are often neutral or deleterious to individual fitness but can also provide genetic diversity driving evolution. Mutagenesis in bacteria contributes to the already serious and growing problem of antibiotic resistance. However, the negative impacts of spontaneous mutagenesis on human health are not limited to bacterial antibiotic resistance. Spontaneous mutations also underlie tumorigenesis and evolution of drug resistance. To better understand the causes of genetic change and how they may be manipulated in order to curb antibiotic resistance or the development of cancer, we must acquire a mechanistic understanding of the major sources of mutagenesis. Bacterial systems are particularly well-suited to studying mutagenesis because of their fast growth rate and the panoply of available experimental tools, but efforts to understand mutagenic mechanisms can be complicated by the experimental system employed. Here, we review our current understanding of mutagenic mechanisms in bacteria and describe the methods used to study mutagenesis in bacterial systems.
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Affiliation(s)
- Jeremy W Schroeder
- a Department of Bacteriology , University of Wisconsin - Madison , Madison , WI , USA
| | - Ponlkrit Yeesin
- a Department of Bacteriology , University of Wisconsin - Madison , Madison , WI , USA
| | - Lyle A Simmons
- b Department of Molecular, Cellular, and Developmental Biology , University of Michigan , Ann Arbor , MI , USA
| | - Jue D Wang
- a Department of Bacteriology , University of Wisconsin - Madison , Madison , WI , USA
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17
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Conflict Resolution in the Genome: How Transcription and Replication Make It Work. Cell 2017; 167:1455-1467. [PMID: 27912056 DOI: 10.1016/j.cell.2016.09.053] [Citation(s) in RCA: 178] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 09/20/2016] [Accepted: 09/27/2016] [Indexed: 01/12/2023]
Abstract
The complex machineries involved in replication and transcription translocate along the same DNA template, often in opposing directions and at different rates. These processes routinely interfere with each other in prokaryotes, and mounting evidence now suggests that RNA polymerase complexes also encounter replication forks in higher eukaryotes. Indeed, cells rely on numerous mechanisms to avoid, tolerate, and resolve such transcription-replication conflicts, and the absence of these mechanisms can lead to catastrophic effects on genome stability and cell viability. In this article, we review the cellular responses to transcription-replication conflicts and highlight how these inevitable encounters shape the genome and impact diverse cellular processes.
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18
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Pif1-family helicases cooperatively suppress widespread replication-fork arrest at tRNA genes. Nat Struct Mol Biol 2016; 24:162-170. [PMID: 27991904 PMCID: PMC5296403 DOI: 10.1038/nsmb.3342] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 11/14/2016] [Indexed: 12/03/2022]
Abstract
Saccharomyces cerevisiae encodes two distinct Pif1-family helicases – Pif1 and Rrm3 – which have been reported to play distinct roles in numerous nuclear processes. Here, we systematically characterize the roles of Pif1 helicases in replisome progression and lagging-strand synthesis in S. cerevisiae. We demonstrate that either Pif1 or Rrm3 redundantly stimulate strand-displacement by DNA polymerase δ during lagging-strand synthesis. By analyzing replisome mobility in pif1 and rrm3 mutants, we show that Rrm3, with a partially redundant contribution from Pif1, suppresses widespread terminal arrest of the replisome at tRNA genes. Although both head-on and codirectional collisions induce replication fork arrest at tRNA genes, head-on collisions arrest a higher proportion of replisomes. Consistent with this observation, we find that head-on collisions between tRNA transcription and replication are under-represented in the S. cerevisiae genome. We demonstrate that tRNA-mediated arrest is R-loop independent, and propose that replisome arrest and DNA damage are mechanistically separable.
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19
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The nature of mutations induced by replication–transcription collisions. Nature 2016; 535:178-81. [PMID: 27362223 PMCID: PMC4945378 DOI: 10.1038/nature18316] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 05/11/2016] [Indexed: 12/18/2022]
Abstract
The DNA replication and transcription machineries share a common DNA template and thus can collide with each other co-directionally or head-on1,2. Replication-transcription collisions can cause replication fork arrest, premature transcription termination, DNA breaks, and recombination intermediates threatening genome integrity1–10. Collisions may also trigger mutations, which are major contributors of genetic disease and evolution5,7,11. However, the nature and mechanisms of collision-induced mutagenesis remain poorly understood. Here we reveal the genetic consequence of replication-transcription collisions in actively dividing bacteria to be two classes of mutations: duplications/deletions and base substitutions in promoters. Both signatures are highly deleterious but are distinct from the well-characterized base substitutions in coding sequence. Duplications/deletions are likely caused by replication stalling events that are triggered by collisions; their distribution patterns are consistent with where the fork first encounters a transcription complex upon entering a transcription unit. Promoter substitutions result mostly from head-on collisions and frequently occur at a nucleotide conserved in promoters recognized by the major sigma factor in bacteria. This substitution is generated via adenine deamination on the template strand in the promoter open complex, as a consequence of head-on replication perturbing transcription initiation. We conclude that replication-transcription collisions induce distinct mutation signatures by antagonizing replication and transcription, not only in coding sequences but also in gene regulatory elements.
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20
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New Insights into the Functions of Transcription Factors that Bind the RNA Polymerase Secondary Channel. Biomolecules 2015; 5:1195-209. [PMID: 26120903 PMCID: PMC4598747 DOI: 10.3390/biom5031195] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/06/2015] [Accepted: 06/09/2015] [Indexed: 11/25/2022] Open
Abstract
Transcription elongation is regulated at several different levels, including control by various accessory transcription elongation factors. A distinct group of these factors interacts with the RNA polymerase secondary channel, an opening at the enzyme surface that leads to its active center. Despite investigation for several years, the activities and in vivo roles of some of these factors remain obscure. Here, we review the recent progress in understanding the functions of the secondary channel binding factors in bacteria. In particular, we highlight the surprising role of global regulator DksA in fidelity of RNA synthesis and the resolution of RNA polymerase traffic jams by the Gre factor. These findings indicate a potential link between transcription fidelity and collisions of the transcription and replication machineries.
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21
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Hoffman EA, McCulley A, Haarer B, Arnak R, Feng W. Break-seq reveals hydroxyurea-induced chromosome fragility as a result of unscheduled conflict between DNA replication and transcription. Genome Res 2015; 25:402-12. [PMID: 25609572 PMCID: PMC4352882 DOI: 10.1101/gr.180497.114] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We have previously demonstrated that in Saccharomyces cerevisiae replication, checkpoint inactivation via a mec1 mutation leads to chromosome breakage at replication forks initiated from virtually all origins after transient exposure to hydroxyurea (HU), an inhibitor of ribonucleotide reductase. Here we sought to determine whether all replication forks containing single-stranded DNA gaps have equal probability of producing double-strand breaks (DSBs) when cells attempt to recover from HU exposure. We devised a new methodology, Break-seq, that combines our previously described DSB labeling with next generation sequencing to map chromosome breaks with improved sensitivity and resolution. We show that DSBs preferentially occur at genes transcriptionally induced by HU. Notably, different subsets of the HU-induced genes produced DSBs in MEC1 and mec1 cells as replication forks traversed a greater distance in MEC1 cells than in mec1 cells during recovery from HU. Specifically, while MEC1 cells exhibited chromosome breakage at stress-response transcription factors, mec1 cells predominantly suffered chromosome breakage at transporter genes, many of which are the substrates of those transcription factors. We propose that HU-induced chromosome fragility arises at higher frequency near HU-induced genes as a result of destabilized replication forks encountering transcription factor binding and/or the act of transcription. We further propose that replication inhibitors can induce unscheduled encounters between replication and transcription and give rise to distinct patterns of chromosome fragile sites.
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Affiliation(s)
- Elizabeth A Hoffman
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Andrew McCulley
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Brian Haarer
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Remigiusz Arnak
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
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22
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Duch A, de Nadal E, Posas F. Dealing with transcriptional outbursts during S phase to protect genomic integrity. J Mol Biol 2013; 425:4745-55. [PMID: 24021813 DOI: 10.1016/j.jmb.2013.08.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/16/2013] [Accepted: 08/23/2013] [Indexed: 10/26/2022]
Abstract
Transcription during S phase needs to be spatially and temporally regulated to prevent collisions between the transcription and replication machineries. Cells have evolved a number of mechanisms to make both processes compatible under normal growth conditions. When conflict management fails, the head-on encounter between RNA and DNA polymerases results in genomic instability unless conflict resolution mechanisms are activated. Nevertheless, there are specific situations in which cells need to dramatically change their transcriptional landscape to adapt to environmental challenges. Signal transduction pathways, such as stress-activated protein kinases (SAPKs), serve to regulate gene expression in response to environmental insults. Prototypical members of SAPKs are the yeast Hog1 and mammalian p38. In response to stress, p38/Hog1 SAPKs control transcription and also regulate cell cycle progression. When yeast cells are stressed during S phase, Hog1 promotes gene induction and, remarkably, also delays replication by directly affecting early origin firing and fork progression. Therefore, by delaying replication, Hog1 plays a key role in preventing conflicts between RNA and DNA polymerases. In this review, we focus on the genomic determinants and mechanisms that make compatible transcription with replication during S phase to prevent genomic instability, especially in response to environmental changes.
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Affiliation(s)
- Alba Duch
- Cell Signaling Unit, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, E-08003 Barcelona, Spain
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23
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Xu W, Mao N, Zhang J. Graphene: a platform for surface-enhanced Raman spectroscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:1206-24. [PMID: 23529788 DOI: 10.1002/smll.201203097] [Citation(s) in RCA: 250] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 01/22/2013] [Indexed: 05/20/2023]
Abstract
Surface-enhanced Raman spectroscopy (SERS) imparts Raman spectroscopy with the capability of detecting analytes at the single-molecule level, but the costs are also manifold, such as a loss of signal reproducibility. Despite remarkable steps having been taken, presently SERS still seems too young to shoulder analytical missions in various practical situations. By the virtue of its unique molecular structure and physical/chemical properties, the rise of graphene opens up a unique platform for SERS studies. In this review, the multi-role of graphene played in SERS is overviewed, including as a Raman probe, as a substrate, as an additive, and as a building block for a flat surface for SERS. Apart from versatile improvements of SERS performance towards applications, graphene-involved SERS studies are also expected to shed light on the fundamental mechanism of the SERS effect.
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Affiliation(s)
- Weigao Xu
- Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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24
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Gaillard H, Herrera-Moyano E, Aguilera A. Transcription-associated genome instability. Chem Rev 2013; 113:8638-61. [PMID: 23597121 DOI: 10.1021/cr400017y] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Hélène Gaillard
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla , Av. Américo Vespucio s/n, 41092 Seville, Spain
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25
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Shao YJ, Hu XQ, Peng GD, Wang RX, Gao RN, Lin C, Shen WD, Li R, Li B. Structure and evolution of the mitochondrial genome of Exorista sorbillans: the Tachinidae (Diptera: Calyptratae) perspective. Mol Biol Rep 2012; 39:11023-30. [PMID: 23053992 DOI: 10.1007/s11033-012-2005-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 10/01/2012] [Indexed: 11/28/2022]
Abstract
The first complete mitochondrial genome (mitogenome) of Tachinidae Exorista sorbillans (Diptera) is sequenced by PCR-based approach. The circular mitogenome is 14,960 bp long and has the representative mitochondrial gene (mt gene) organization and order of Diptera. All protein-coding sequences are initiated with ATN codon; however, the only exception is Cox I gene, which has a 4-bp ATCG putative start codon. Ten of the thirteen protein-coding genes have a complete termination codon (TAA), but the rest are seated on the H strand with incomplete codons. The mitogenome of E. sorbillans is biased toward A+T content at 78.4 %, and the strand-specific bias is in reflection of the third codon positions of mt genes, and their T/C ratios as strand indictor are higher on the H strand more than those on the L strand pointing at any strain of seven Diptera flies. The length of the A+T-rich region of E. sorbillans is 106 bp, including a tandem triple copies of a13-bp fragment. Compared to Haematobia irritans, E. sorbillans holds distant relationship with Drosophila. Phylogenetic topologies based on the amino acid sequences, supporting that E. sorbillans (Tachinidae) is clustered with strains of Calliphoridae and Oestridae, and superfamily Oestroidea are polyphyletic groups with Muscidae in a clade.
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Affiliation(s)
- Yuan-jun Shao
- School of Basic Medicine and Biological Sciences, Soochow University, Jiangsu, 215123, People's Republic of China.
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26
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Zhang Y, Shishkin AA, Nishida Y, Marcinkowski-Desmond D, Saini N, Volkov KV, Mirkin SM, Lobachev KS. Genome-wide screen identifies pathways that govern GAA/TTC repeat fragility and expansions in dividing and nondividing yeast cells. Mol Cell 2012; 48:254-65. [PMID: 22959270 DOI: 10.1016/j.molcel.2012.08.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 07/06/2012] [Accepted: 08/02/2012] [Indexed: 12/20/2022]
Abstract
Triplex structure-forming GAA/TTC repeats pose a dual threat to the eukaryotic genome integrity. Their potential to expand can lead to gene inactivation, the cause of Friedreich's ataxia disease in humans. In model systems, long GAA/TTC tracts also act as chromosomal fragile sites that can trigger gross chromosomal rearrangements. The mechanisms that regulate the metabolism of GAA/TTC repeats are poorly understood. We have developed an experimental system in the yeast Saccharomyces cerevisiae that allows us to systematically identify genes crucial for maintaining the repeat stability. Two major groups of mutants defective in DNA replication or transcription initiation are found to be prone to fragility and large-scale expansions. We demonstrate that problems imposed by the repeats during DNA replication in actively dividing cells and during transcription initiation in nondividing cells can culminate in genome instability. We propose that similar mechanisms can mediate detrimental metabolism of GAA/TTC tracts in human cells.
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Affiliation(s)
- Yu Zhang
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
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27
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Abstract
DNA replication and transcription use the same template and occur concurrently in bacteria. The lack of temporal and spatial separation of these two processes leads to their conflict, and failure to deal with this conflict can result in genome alterations and reduced fitness. In recent years major advances have been made in understanding how cells avoid conflicts between replication and transcription and how such conflicts are resolved when they do occur. In this Review, we summarize these findings, which shed light on the significance of the problem and on how bacterial cells deal with unwanted encounters between the replication and transcription machineries.
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28
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Abstract
There is mounting evidence that there are frequent conflicts between complexes that replicate DNA and those that transcribe the same template, and that these conflicts lead to blockage of replication and genome instability. Such problems are perhaps best understood in bacteria, but it is becoming apparent that replicative barriers associated with transcription are a universal feature of life. This review summarizes what is currently known about how collisions between replisomes and transcription complexes are minimized and the mechanisms that help to resolve such collisions when they do occur. Although our understanding of these processes is still far from complete, a picture is emerging of a wide variety of different types of transcriptional blocks to replication that have resulted in a complex, overlapping system of mechanisms to avoid or tolerate such collisions.
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Affiliation(s)
- Peter McGlynn
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, UK.
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29
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Castro-Roa D, Zenkin N. In vitro experimental system for analysis of transcription-translation coupling. Nucleic Acids Res 2011; 40:e45. [PMID: 22210860 PMCID: PMC3315309 DOI: 10.1093/nar/gkr1262] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Transcription and translation are coupled in bacteria, meaning that translation takes place co-transcriptionally. During transcription–translation, both machineries mutually affect each others’ functions, which is important for regulation of gene expression. Analysis of interactions between RNA polymerase (RNAP) and the ribosome, however, are limited due to the lack of an in vitro experimental system. Here, we report the development of an in vitro transcription coupled to translation system assembled from purified components. The system allows controlled stepwise transcription and simultaneous stepwise translation of the nascent RNA, and permits investigation of the interactions of RNAP with the ribosome, as well as the effects of translation on transcription and transcription on translation. As an example of usage of this experimental system, we uncover complex effects of transcription–translation coupling on pausing of transcription.
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Affiliation(s)
- Daniel Castro-Roa
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK
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30
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Pomerantz RT, O'Donnell M. What happens when replication and transcription complexes collide? Cell Cycle 2011; 9:2537-43. [PMID: 20581460 DOI: 10.4161/cc.9.13.12122] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The arrest of replication forks due to collisions with transcription complexes leads to genomic instability and cell death. Mechanisms that promote the progression of replication forks past transcription complexes are therefore essential for propagation and preservation of the genome. Recent studies of E. coli directly investigate the consequences of collisions of the replisome with RNAP polymerase (RNAP) in vitro and provide novel mechanisms by which these encounters may be resolved. Additionally, recent in vivo and in vitro studies support the longstanding hypothesis that auxiliary DNA helicases promote replication through roadblocks such as transcription complexes. Here we review past and recent advances that formulate our current understanding of how the bacterial replisome deals with transcription complexes along the path of chromosome duplication.
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Affiliation(s)
- Richard T Pomerantz
- The Rockefeller University, Howard Hughes Medical Institute, New York, NY, USA
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31
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Merrikh H, Machón C, Grainger WH, Grossman AD, Soultanas P. Co-directional replication-transcription conflicts lead to replication restart. Nature 2011; 470:554-7. [PMID: 21350489 PMCID: PMC3059490 DOI: 10.1038/nature09758] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Accepted: 12/09/2010] [Indexed: 11/23/2022]
Abstract
Head-on encounters between the replication and transcription machineries on the lagging DNA strand can lead to replication fork arrest and genomic instability. To avoid head-on encounters, most genes, especially essential and highly transcribed genes, are encoded on the leading strand such that transcription and replication are co-directional. Virtually all bacteria have the highly expressed ribosomal RNA genes co-directional with replication. In bacteria, co-directional encounters seem inevitable because the rate of replication is about 10-20-fold greater than the rate of transcription. However, these encounters are generally thought to be benign. Biochemical analyses indicate that head-on encounters are more deleterious than co-directional encounters and that in both situations, replication resumes without the need for any auxiliary restart proteins, at least in vitro. Here we show that in vivo, co-directional transcription can disrupt replication, leading to the involvement of replication restart proteins. We found that highly transcribed rRNA genes are hotspots for co-directional conflicts between replication and transcription in rapidly growing Bacillus subtilis cells. We observed a transcription-dependent increase in association of the replicative helicase and replication restart proteins where head-on and co-directional conflicts occur. Our results indicate that there are co-directional conflicts between replication and transcription in vivo. Furthermore, in contrast to the findings in vitro, the replication restart machinery is involved in vivo in resolving potentially deleterious encounters due to head-on and co-directional conflicts. These conflicts probably occur in many organisms and at many chromosomal locations and help to explain the presence of important auxiliary proteins involved in replication restart and in helping to clear a path along the DNA for the replisome.
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Affiliation(s)
- Houra Merrikh
- Department of Biology, Building 68-530, M.I.T., Cambridge, MA, 02139, USA
| | - Cristina Machón
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - William H. Grainger
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Alan D. Grossman
- Department of Biology, Building 68-530, M.I.T., Cambridge, MA, 02139, USA
| | - Panos Soultanas
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
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32
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Lubelsky Y, Sasaki T, Kuipers MA, Lucas I, Le Beau MM, Carignon S, Debatisse M, Prinz JA, Dennis JH, Gilbert DM. Pre-replication complex proteins assemble at regions of low nucleosome occupancy within the Chinese hamster dihydrofolate reductase initiation zone. Nucleic Acids Res 2010; 39:3141-55. [PMID: 21148149 PMCID: PMC3082903 DOI: 10.1093/nar/gkq1276] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Genome-scale mapping of pre-replication complex proteins has not been reported in mammalian cells. Poor enrichment of these proteins at specific sites may be due to dispersed binding, poor epitope availability or cell cycle stage-specific binding. Here, we have mapped sites of biotin-tagged ORC and MCM protein binding in G1-synchronized populations of Chinese hamster cells harboring amplified copies of the dihydrofolate reductase (DHFR) locus, using avidin-affinity purification of biotinylated chromatin followed by high-density microarray analysis across the DHFR locus. We have identified several sites of significant enrichment for both complexes distributed throughout the previously identified initiation zone. Analysis of the frequency of initiations across stretched DNA fibers from the DHFR locus confirmed a broad zone of de-localized initiation activity surrounding the sites of ORC and MCM enrichment. Mapping positions of mononucleosomal DNA empirically and computing nucleosome-positioning information in silico revealed that ORC and MCM map to regions of low measured and predicted nucleosome occupancy. Our results demonstrate that specific sites of ORC and MCM enrichment can be detected within a mammalian intitiation zone, and suggest that initiation zones may be regions of generally low nucleosome occupancy where flexible nucleosome positioning permits flexible pre-RC assembly sites.
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Affiliation(s)
- Yoav Lubelsky
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
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33
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Ton-Hoang B, Pasternak C, Siguier P, Guynet C, Hickman AB, Dyda F, Sommer S, Chandler M. Single-stranded DNA transposition is coupled to host replication. Cell 2010; 142:398-408. [PMID: 20691900 DOI: 10.1016/j.cell.2010.06.034] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 04/03/2010] [Accepted: 05/17/2010] [Indexed: 10/19/2022]
Abstract
DNA transposition has contributed significantly to evolution of eukaryotes and prokaryotes. Insertion sequences (ISs) are the simplest prokaryotic transposons and are divided into families on the basis of their organization and transposition mechanism. Here, we describe a link between transposition of IS608 and ISDra2, both members of the IS200/IS605 family, which uses obligatory single-stranded DNA intermediates, and the host replication fork. Replication direction through the IS plays a crucial role in excision: activity is maximal when the "top" IS strand is located on the lagging-strand template. Excision is stimulated upon transient inactivation of replicative helicase function or inhibition of Okazaki fragment synthesis. IS608 insertions also exhibit an orientation preference for the lagging-strand template and insertion can be specifically directed to stalled replication forks. An in silico genomic approach provides evidence that dissemination of other IS200/IS605 family members is also linked to host replication.
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Affiliation(s)
- Bao Ton-Hoang
- Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de Recherche Scientifique, Unité Mixte de Recherche 5100, 118 Route de Narbonne, F31062 Toulouse Cedex, France.
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34
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Pomerantz RT, O'Donnell M. Polymerase trafficking: A role for transcription factors in preventing replication fork arrest. Transcription 2010; 1:136-139. [PMID: 21326887 DOI: 10.4161/trns.1.3.13488] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 07/26/2010] [Accepted: 08/30/2010] [Indexed: 11/19/2022] Open
Abstract
Replication forks and transcription complexes often collide, which can result in mutagenesis and chromosomal rearrangements. Recent studies of E. coli demonstrate a role for transcription factors in reducing conflicts between replication and transcription. These findings suggest that transcription regulators preserve genome integrity by preventing replication fork arrest.
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Affiliation(s)
- Richard T Pomerantz
- The Rockefeller University; Howard Hughes Medical Institute; New York, NY USA
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35
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Stepanova E, Wang M, Severinov K, Borukhov S. Early transcriptional arrest at Escherichia coli rplN and ompX promoters. J Biol Chem 2010; 284:35702-13. [PMID: 19854830 DOI: 10.1074/jbc.m109.053983] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacterial transcription elongation factors GreA and GreB stimulate the intrinsic RNase activity of RNA polymerase (RNAP), thus helping the enzyme to read through pausing and arresting sites on DNA. Gre factors also accelerate RNAP transition from initiation to elongation. Here, we characterized the molecular mechanism by which Gre factors facilitate transcription at two Escherichia coli promoters, PrplN and PompX, that require GreA for optimal in vivo activity. Using in vitro transcription assays, KMnO(4) footprinting, and Fe(2+)-induced hydroxyl radical mapping, we show that during transcription initiation at PrplN and PompX in the absence of Gre factors, RNAP falls into a condition of promoter-proximal transcriptional arrest that prevents production of full-length transcripts both in vitro and in vivo. Arrest occurs when RNAP synthesizes 9-14-nucleotide-long transcripts and backtracks by 5-7 (PrplN) or 2-4 (PompX) nucleotides. Initiation factor sigma(70) contributes to the formation of arrested complexes at both promoters. The signal for promoter-proximal arrest at PrplN is bipartite and requires two elements: the extended -10 promoter element and the initial transcribed region from positions +2 to +6. GreA and GreB prevent arrest at PrplN and PompX by inducing cleavage of the 3'-proximal backtracked portion of RNA at the onset of arrested complex formation and stimulate productive transcription by allowing RNAP to elongate the 5'-proximal transcript cleavage products in the presence of substrates. We propose that promoter-proximal arrest is a common feature of many bacterial promoters and may represent an important physiological target of regulation by transcript cleavage factors.
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Affiliation(s)
- Ekaterina Stepanova
- Department of Cell Biology, School of Osteopathic Medicine at Stratford, University of Medicine and Dentistry of New Jersey, Stratford, New Jersey 08084, USA
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36
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Boubakri H, de Septenville AL, Viguera E, Michel B. The helicases DinG, Rep and UvrD cooperate to promote replication across transcription units in vivo. EMBO J 2009; 29:145-57. [PMID: 19851282 PMCID: PMC2770101 DOI: 10.1038/emboj.2009.308] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 09/23/2009] [Indexed: 11/22/2022] Open
Abstract
How living cells deal with head-on collisions of the replication and transcription complexes has been debated for a long time. Even in the widely studied model bacteria Escherichia coli, the enzymes that take care of such collisions are still unknown. We report here that in vivo, the DinG, Rep and UvrD helicases are essential for efficient replication across highly transcribed regions. We show that when rRNA operons (rrn) are inverted to face replication, the viability of the dinG mutant is affected and over-expression of RNase H rescues the growth defect, showing that DinG acts in vivo to remove R-loops. In addition, DinG, Rep and UvrD exert a common function, which requires the presence of two of these three helicases. After replication blockage by an inverted rrn, Rep in conjunction with DinG or UvrD removes RNA polymerase, a task that is fulfilled in its absence by the SOS-induced DinG and UvrD helicases. Finally, Rep and UvrD also act at inverted sequences other than rrn, and promote replication through highly transcribed regions in wild-type E. coli.
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Affiliation(s)
- Hasna Boubakri
- CNRS, Centre de Génétique Moléculaire, FRE 3144, Gif-sur-Yvette, France
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37
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Azvolinsky A, Giresi PG, Lieb JD, Zakian VA. Highly transcribed RNA polymerase II genes are impediments to replication fork progression in Saccharomyces cerevisiae. Mol Cell 2009; 34:722-34. [PMID: 19560424 DOI: 10.1016/j.molcel.2009.05.022] [Citation(s) in RCA: 231] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 04/21/2009] [Accepted: 05/29/2009] [Indexed: 10/20/2022]
Abstract
Replication forks face multiple obstacles that slow their progression. By two-dimensional gel analysis, yeast forks pause at stable DNA protein complexes, and this pausing is greatly increased in the absence of the Rrm3 helicase. We used a genome-wide approach to identify 96 sites of very high DNA polymerase binding in wild-type cells. Most of these binding sites were not previously identified pause sites. Rather, the most highly represented genomic category among high DNA polymerase binding sites was the open reading frames (ORFs) of highly transcribed RNA polymerase II genes. Twice as many pause sites were identified in rrm3 compared with wild-type cells, as pausing in this strain occurred at both highly transcribed RNA polymerase II genes and the previously identified protein DNA complexes. ORFs of highly transcribed RNA polymerase II genes are a class of natural pause sites that are not exacerbated in rrm3 cells.
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Affiliation(s)
- Anna Azvolinsky
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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38
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Balleza E, López-Bojorquez LN, Martínez-Antonio A, Resendis-Antonio O, Lozada-Chávez I, Balderas-Martínez YI, Encarnación S, Collado-Vides J. Regulation by transcription factors in bacteria: beyond description. FEMS Microbiol Rev 2009; 33:133-51. [PMID: 19076632 PMCID: PMC2704942 DOI: 10.1111/j.1574-6976.2008.00145.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Transcription is an essential step in gene expression and its understanding has been one of the major interests in molecular and cellular biology. By precisely tuning gene expression, transcriptional regulation determines the molecular machinery for developmental plasticity, homeostasis and adaptation. In this review, we transmit the main ideas or concepts behind regulation by transcription factors and give just enough examples to sustain these main ideas, thus avoiding a classical ennumeration of facts. We review recent concepts and developments: cis elements and trans regulatory factors, chromosome organization and structure, transcriptional regulatory networks (TRNs) and transcriptomics. We also summarize new important discoveries that will probably affect the direction of research in gene regulation: epigenetics and stochasticity in transcriptional regulation, synthetic circuits and plasticity and evolution of TRNs. Many of the new discoveries in gene regulation are not extensively tested with wetlab approaches. Consequently, we review this broad area in Inference of TRNs and Dynamical Models of TRNs. Finally, we have stepped backwards to trace the origins of these modern concepts, synthesizing their history in a timeline schema.
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Affiliation(s)
- Enrique Balleza
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
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39
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Abstract
Many bacterial cellular processes interact intimately with the chromosome. Such interplay is the major driving force of genome structure or organization. Interactions take place at different scales-local for gene expression, global for replication-and lead to the differentiation of the chromosome into organizational units such as operons, replichores, or macrodomains. These processes are intermingled in the cell and create complex higher-level organizational features that are adaptive because they favor the interplay between the processes. The surprising result of selection for genome organization is that gene repertoires change much more quickly than chromosomal structure. Comparative genomics and experimental genomic manipulations are untangling the different cellular and evolutionary mechanisms causing such resilience to change. Since organization results from cellular processes, a better understanding of chromosome organization will help unravel the underlying cellular processes and their diversity.
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Affiliation(s)
- Eduardo P C Rocha
- Institut Pasteur, Microbial Evolutionary Genomics, F-75015 Paris, France.
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40
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Tychinsky VP, Kretushev AV, Klemyashov IV, Vyshenskaya TV, Filippova NA, Raikhlin NT, Shtil AA. Quantitative real-time analysis of nucleolar stress by coherent phase microscopy. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:064032. [PMID: 19123678 DOI: 10.1117/1.3042241] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We develop a method of coherent phase microscopy (CPM) for direct visualization of nonfixed, nonstained mammalian cells (both cultured cells and freshly isolated tumor biopsies) followed by computer-assisted data analysis. The major purpose of CPM is to evaluate the refractive properties of optically dense intracellular structures such as the nucleus and the nucleoli. In particular, we focus on quantitative real-time analysis of the nucleolar dynamics using phase thickness as an equivalent of optical path difference for optically nonhomogenous biological objects. Pharmacological inhibition of gene transcription leads to a dramatic decrease of the phase thickness of the nucleoli within the initial minutes of cell exposure. Furthermore, the acute depletion of intracellular ATP pool, depolymerization of microtubules and inhibition of DNA replication resulted in a rapid decrease of the nucleolar phase thickness. These optical effects were paralleled by segregation of nucleolar components as documented by electron microscopy. Thus, CPM detects early changes of nucleolar dynamics, in particular, the nucleolar segregation as part of general cellular response to cytotoxic stress, regardless of whether the nucleolus is or is not the primary target of the toxin. CPM is applicable for monitoring and quantitative analysis of the "nucleolar stress" in living mammalian cells.
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Affiliation(s)
- Vladimir P Tychinsky
- Moscow Institute of Radioengineering, Electronics and Automation, 78 Vernadsky Avenue Moscow 119454, Russia.
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41
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Mayán-Santos MD, Martínez-Robles ML, Hernández P, Schvartzman JB, Krimer DB. A redundancy of processes that cause replication fork stalling enhances recombination at two distinct sites in yeast rDNA. Mol Microbiol 2008; 69:361-75. [PMID: 18485068 DOI: 10.1111/j.1365-2958.2008.06278.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
DNA recombination was investigated by monitoring integration at the rDNA of a circular minichromosome containing a 35S minigene and a replication fork barrier (RFB). The effects of replication fork stalling on integration were studied in wild-type, FOB1Delta, SIR2Delta and the double mutant FOB1DeltaSIR2Delta cells. The results obtained confirmed that Sir2p represses and replication fork stalling enhances integration of the minichromosome. This integration, however, only took place at two distinct sites: the RFB and the 3' end of the 35S gene. For integration to take place at the 35S gene, replication fork stalling must occur at the 3' end of the gene in both the minichromosome and the chromosomal repeats. Integration at the RFB, on the other hand, occurred readily in FOB1Delta cells, indicating that more than a single mechanism triggers homologous recombination at this site. Altogether, these observations strongly suggest that the main role for replication fork stalling at the rDNA locus is to promote homologous recombination rather than just to prevent head-on collision of transcription and replication as originally thought.
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Affiliation(s)
- M D Mayán-Santos
- Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
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42
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Esnault E, Valens M, Espéli O, Boccard F. Chromosome structuring limits genome plasticity in Escherichia coli. PLoS Genet 2008; 3:e226. [PMID: 18085828 PMCID: PMC2134941 DOI: 10.1371/journal.pgen.0030226] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Accepted: 11/06/2007] [Indexed: 11/22/2022] Open
Abstract
Chromosome organizations of related bacterial genera are well conserved despite a very long divergence period. We have assessed the forces limiting bacterial genome plasticity in Escherichia coli by measuring the respective effect of altering different parameters, including DNA replication, compositional skew of replichores, coordination of gene expression with DNA replication, replication-associated gene dosage, and chromosome organization into macrodomains. Chromosomes were rearranged by large inversions. Changes in the compositional skew of replichores, in the coordination of gene expression with DNA replication or in the replication-associated gene dosage have only a moderate effect on cell physiology because large rearrangements inverting the orientation of several hundred genes inside a replichore are only slightly detrimental. By contrast, changing the balance between the two replication arms has a more drastic effect, and the recombinational rescue of replication forks is required for cell viability when one of the chromosome arms is less than half than the other one. Macrodomain organization also appears to be a major factor restricting chromosome plasticity, and two types of inverted configurations severely affect the cell cycle. First, the disruption of the Ter macrodomain with replication forks merging far from the normal replichore junction provoked chromosome segregation defects. The second major problematic configurations resulted from inversions between Ori and Right macrodomains, which perturb nucleoid distribution and early steps of cytokinesis. Consequences for the control of the bacterial cell cycle and for the evolution of bacterial chromosome configuration are discussed. Genomic analyses have revealed that bacterial genomes are dynamic entities that evolve through various processes including intrachromosome genetic rearrangements, gene duplication, and gene loss or acquisition by gene transfer. Nevertheless, comparison of bacterial chromosomes from related genera revealed a conservation of genetic organization. Most bacterial genomes are circular molecules, and DNA replication proceeds bidirectionally from a single origin to an opposite region where replication forks meet. The replication process imprints the bacterial chromosome because initiation and termination at defined loci result in strand biases due to the mutational differences occurring during leading and lagging strands synthesis. We analyze the strength of different parameters that may limit genome plasticity. We show that the preferential positioning of essential genes on the leading strand, the proximity of genes involved in transcription and translation to the origin of replication on the leading strand, and the presence of biased motifs along the replichores operate only as long-term positive selection determinants. By contrast, selection operates to maintain replication arms of similar lengths. Finally, we demonstrate that spatial structuring of the chromosome impedes strongly genome plasticity. Genetic evidence supports the presence of two steps in the cell cycle controlled by the spatial organization of the chromosome.
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Affiliation(s)
- Emilie Esnault
- Centre de Génétique Moléculaire du CNRS, 91198 Gif-sur-Yvette, France
| | - Michèle Valens
- Centre de Génétique Moléculaire du CNRS, 91198 Gif-sur-Yvette, France
| | - Olivier Espéli
- Centre de Génétique Moléculaire du CNRS, 91198 Gif-sur-Yvette, France
| | - Frédéric Boccard
- Centre de Génétique Moléculaire du CNRS, 91198 Gif-sur-Yvette, France
- * To whom correspondence should be addressed. E-mail:
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43
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Abstract
Accurate and complete replication of the genome in every cell division is a prerequisite of genomic stability. Thus, both prokaryotic and eukaryotic replication forks are extremely precise and robust molecular machines that have evolved to be up to the task. However, it has recently become clear that the replication fork is more of a hurdler than a runner: it must overcome various obstacles present on its way. Such obstacles can be called natural impediments to DNA replication, as opposed to external and genetic factors. Natural impediments to DNA replication are particular DNA binding proteins, unusual secondary structures in DNA, and transcription complexes that occasionally (in eukaryotes) or constantly (in prokaryotes) operate on replicating templates. This review describes the mechanisms and consequences of replication stalling at various natural impediments, with an emphasis on the role of replication stalling in genomic instability.
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Affiliation(s)
- Ekaterina V. Mirkin
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60607
| | - Sergei M. Mirkin
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60607
- Corresponding author. Present address: Department of Biology, Tufts University, Medford, MA 02155. Phone: (617) 627-4794. Fax: (617) 627-3805. E-mail:
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44
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Fierro-Fernández M, Hernández P, Krimer DB, Schvartzman JB. Replication fork reversal occurs spontaneously after digestion but is constrained in supercoiled domains. J Biol Chem 2007; 282:18190-18196. [PMID: 17456472 DOI: 10.1074/jbc.m701559200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Replication fork reversal was investigated in undigested and linearized replication intermediates of bacterial DNA plasmids containing a stalled fork. Two-dimensional agarose gel electrophoresis, a branch migration and extrusion assay, electron microscopy, and DNA-psoralen cross-linking were used to show that extensive replication fork reversal and extrusion of the nascent-nascent duplex occurs spontaneously after DNA nicking and restriction enzyme digestion but that fork retreat is severely limited in covalently closed supercoiled domains.
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Affiliation(s)
- Marta Fierro-Fernández
- Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Pablo Hernández
- Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Dora B Krimer
- Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Jorge B Schvartzman
- Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain.
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45
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Wang JD, Berkmen MB, Grossman AD. Genome-wide coorientation of replication and transcription reduces adverse effects on replication in Bacillus subtilis. Proc Natl Acad Sci U S A 2007; 104:5608-13. [PMID: 17372224 PMCID: PMC1838449 DOI: 10.1073/pnas.0608999104] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In many bacteria, there is a strong bias for genes to be encoded on the leading strand of DNA, resulting in coorientation of replication and transcription. In Bacillus subtilis, transcription of the majority of genes (75%) is cooriented with replication. By using genome-wide profiling of replication with DNA microarrays, we found that this coorientation bias reduces adverse effects of transcription on replication. We found that in wild-type cells, transcription did not appear to affect the rate of replication elongation. However, in mutants with reversed transcription bias for an extended region of the chromosome, replication elongation was slower. This reduced replication rate depended on transcription and was limited to the region in which the directions of replication and transcription are opposed. These results support the hypothesis that the strong bias to coorient transcription and replication is due to selective pressure for processive, efficient, and accurate replication.
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Affiliation(s)
- Jue D. Wang
- Department of Biology, Building 68-530, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Melanie B. Berkmen
- Department of Biology, Building 68-530, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Alan D. Grossman
- Department of Biology, Building 68-530, Massachusetts Institute of Technology, Cambridge, MA 02139
- To whom correspondence should be addressed. E-mail:
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46
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Pomerantz RT, Temiakov D, Anikin M, Vassylyev DG, McAllister WT. A mechanism of nucleotide misincorporation during transcription due to template-strand misalignment. Mol Cell 2006; 24:245-55. [PMID: 17052458 PMCID: PMC2810628 DOI: 10.1016/j.molcel.2006.08.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Revised: 07/15/2006] [Accepted: 08/17/2006] [Indexed: 12/22/2022]
Abstract
Transcription errors by T7 RNA polymerase (RNAP) may occur as the result of a mechanism in which the template base two positions downstream of the 3' end of the RNA (the TSn+1 base) is utilized during two consecutive nucleotide-addition cycles. In the first cycle, misalignment of the template strand leads to incorporation of a nucleotide that is complementary to the TSn+1 base. In the second cycle, the template is realigned and the mismatched primer is efficiently extended, resulting in a substitution error. Proper organization of the transcription bubble is required for maintaining the correct register of the DNA template, as the presence of a complementary nontemplate strand opposite the TSn+1 base suppresses template misalignment. Our findings for T7 RNAP are in contrast to related DNA polymerases of the Pol I type, which fail to extend mismatches efficiently and generate predominantly deletion errors as a result of template-strand misalignment.
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Affiliation(s)
- Richard T. Pomerantz
- Department of Microbiology and Immunology, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, New York 11203, USA
- Graduate Program in Molecular and Cellular Biology, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, New York 11203, USA
| | - Dmitry Temiakov
- Department of Cell Biology, University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, 42 East Laurel Road, Stratford, New Jersey 08084, USA
| | - Michael Anikin
- Department of Cell Biology, University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, 42 East Laurel Road, Stratford, New Jersey 08084, USA
| | - Dmitry G. Vassylyev
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 434 Kaul Genetics Building, 720 20 Street South, Birmingham, AL 35294, USA
| | - William T. McAllister
- Department of Cell Biology, University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, 42 East Laurel Road, Stratford, New Jersey 08084, USA
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47
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Katsnelson A. Genome punctuation. J Biophys Biochem Cytol 2006. [PMCID: PMC2063901 DOI: 10.1083/jcb.1735rr3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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