1
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Sutormin D, Galivondzhyan A, Gafurov A, Severinov K. Single-nucleotide resolution detection of Topo IV cleavage activity in the Escherichia coli genome with Topo-Seq. Front Microbiol 2023; 14:1160736. [PMID: 37089538 PMCID: PMC10117906 DOI: 10.3389/fmicb.2023.1160736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 03/16/2023] [Indexed: 04/08/2023] Open
Abstract
Topoisomerase IV (Topo IV) is the main decatenation enzyme in Escherichia coli; it removes catenation links that are formed during DNA replication. Topo IV binding and cleavage sites were previously identified in the E. coli genome with ChIP-Seq and NorfIP. Here, we used a more sensitive, single-nucleotide resolution Topo-Seq procedure to identify Topo IV cleavage sites (TCSs) genome-wide. We detected thousands of TCSs scattered in the bacterial genome. The determined cleavage motif of Topo IV contained previously known cleavage determinants (−4G/+8C, −2A/+6 T, −1 T/+5A) and additional, not observed previously, positions −7C/+11G and −6C/+10G. TCSs were depleted in the Ter macrodomain except for two exceptionally strong non-canonical cleavage sites located in 33 and 38 bp from the XerC-box of the dif-site. Topo IV cleavage activity was increased in Left and Right macrodomains flanking the Ter macrodomain and was especially high in the 50–60 kb region containing the oriC origin of replication. Topo IV enrichment was also increased downstream of highly active transcription units, indicating that the enzyme is involved in relaxation of transcription-induced positive supercoiling.
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Affiliation(s)
- Dmitry Sutormin
- Skolkovo Institute of Science and Technology, Moscow, Russia
- *Correspondence: Dmitry Sutormin,
| | | | - Azamat Gafurov
- Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Konstantin Severinov
- Waksman Institute for Microbiology, Rutgers, The State University of New Jersey, Piscataway, NJ, United States
- Konstantin Severinov,
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2
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Kasho K, Oshima T, Chumsakul O, Nakamura K, Fukamachi K, Katayama T. Whole-Genome Analysis Reveals That the Nucleoid Protein IHF Predominantly Binds to the Replication Origin oriC Specifically at the Time of Initiation. Front Microbiol 2021; 12:697712. [PMID: 34475859 PMCID: PMC8407004 DOI: 10.3389/fmicb.2021.697712] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 07/26/2021] [Indexed: 11/20/2022] Open
Abstract
The structure and function of bacterial chromosomes are dynamically regulated by a wide variety of nucleoid-associated proteins (NAPs) and DNA superstructures, such as DNA supercoiling. In Escherichia coli, integration host factor (IHF), a NAP, binds to specific transcription promoters and regulatory DNA elements of DNA replication such as the replication origin oriC: binding to these elements depends on the cell cycle but underlying mechanisms are unknown. In this study, we combined GeF-seq (genome footprinting with high-throughput sequencing) with synchronization of the E. coli cell cycle to determine the genome-wide, cell cycle-dependent binding of IHF with base-pair resolution. The GeF-seq results in this study were qualified enough to analyze genomic IHF binding sites (e.g., oriC and the transcriptional promoters of ilvG and osmY) except some of the known sites. Unexpectedly, we found that before replication initiation, oriC was a predominant site for stable IHF binding, whereas all other loci exhibited reduced IHF binding. To reveal the specific mechanism of stable oriC–IHF binding, we inserted a truncated oriC sequence in the terC (replication terminus) locus of the genome. Before replication initiation, stable IHF binding was detected even at this additional oriC site, dependent on the specific DnaA-binding sequence DnaA box R1 within the site. DnaA oligomers formed on oriC might protect the oriC–IHF complex from IHF dissociation. After replication initiation, IHF rapidly dissociated from oriC, and IHF binding to other sites was sustained or stimulated. In addition, we identified a novel locus associated with cell cycle-dependent IHF binding. These findings provide mechanistic insight into IHF binding and dissociation in the genome.
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Affiliation(s)
- Kazutoshi Kasho
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Taku Oshima
- Department of Biotechnology, Toyama Prefectural University, Toyama, Japan
| | - Onuma Chumsakul
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Nara, Japan
| | - Kensuke Nakamura
- Department of Life Science and Informatics, Maebashi Institute of Technology, Maebashi, Japan
| | - Kazuki Fukamachi
- Department of Biotechnology, Toyama Prefectural University, Toyama, Japan
| | - Tsutomu Katayama
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
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3
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Jia R, Song Z, Lin J, Li Z, Shan G, Huang C. Gawky modulates MTF-1-mediated transcription activation and metal discrimination. Nucleic Acids Res 2021; 49:6296-6314. [PMID: 34107019 PMCID: PMC8216474 DOI: 10.1093/nar/gkab474] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 05/12/2021] [Accepted: 05/17/2021] [Indexed: 02/07/2023] Open
Abstract
Metal-induced genes are usually transcribed at relatively low levels under normal conditions and are rapidly activated by heavy metal stress. Many of these genes respond preferentially to specific metal-stressed conditions. However, the mechanism by which the general transcription machinery discriminates metal stress from normal conditions and the regulation of MTF-1-meditated metal discrimination are poorly characterized. Using a focused RNAi screening in Drosophila Schneider 2 (S2) cells, we identified a novel activator, the Drosophila gawky, of metal-responsive genes. Depletion of gawky has almost no effect on the basal transcription of the metallothionein (MT) genes, but impairs the metal-induced transcription by inducing the dissociation of MTF-1 from the MT promoters and the deficient nuclear import of MTF-1 under metal-stressed conditions. This suggests that gawky serves as a 'checkpoint' for metal stress and metal-induced transcription. In fact, regular mRNAs are converted into gawky-controlled transcripts if expressed under the control of a metal-responsive promoter, suggesting that whether transcription undergoes gawky-mediated regulation is encrypted therein. Additionally, lack of gawky eliminates the DNA binding bias of MTF-1 and the transcription preference of metal-specific genes. This suggests a combinatorial control of metal discrimination by gawky, MTF-1, and MTF-1 binding sites.
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Affiliation(s)
- Ruirui Jia
- School of Life Sciences, Chongqing University, Chongqing 401331, China
- Center of Plant Functional Genomics, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing 401331, China
| | - Zhenxing Song
- School of Life Sciences, Chongqing University, Chongqing 401331, China
- Center of Plant Functional Genomics, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing 401331, China
| | - Jiamei Lin
- School of Life Sciences, Chongqing University, Chongqing 401331, China
- Center of Plant Functional Genomics, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing 401331, China
| | - Zhengguo Li
- School of Life Sciences, Chongqing University, Chongqing 401331, China
- Center of Plant Functional Genomics, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing 401331, China
| | - Ge Shan
- School of Basic Medical Sciences, Division of Life Science and Medicine, University of Science and Technology of China, Hefei 230027, China
| | - Chuan Huang
- School of Life Sciences, Chongqing University, Chongqing 401331, China
- Center of Plant Functional Genomics, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing 401331, China
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4
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Sebestyén E, Marullo F, Lucini F, Petrini C, Bianchi A, Valsoni S, Olivieri I, Antonelli L, Gregoretti F, Oliva G, Ferrari F, Lanzuolo C. SAMMY-seq reveals early alteration of heterochromatin and deregulation of bivalent genes in Hutchinson-Gilford Progeria Syndrome. Nat Commun 2020; 11:6274. [PMID: 33293552 PMCID: PMC7722762 DOI: 10.1038/s41467-020-20048-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 11/05/2020] [Indexed: 12/14/2022] Open
Abstract
Hutchinson-Gilford progeria syndrome is a genetic disease caused by an aberrant form of Lamin A resulting in chromatin structure disruption, in particular by interfering with lamina associated domains. Early molecular alterations involved in chromatin remodeling have not been identified thus far. Here, we present SAMMY-seq, a high-throughput sequencing-based method for genome-wide characterization of heterochromatin dynamics. Using SAMMY-seq, we detect early stage alterations of heterochromatin structure in progeria primary fibroblasts. These structural changes do not disrupt the distribution of H3K9me3 in early passage cells, thus suggesting that chromatin rearrangements precede H3K9me3 alterations described at later passages. On the other hand, we observe an interplay between changes in chromatin accessibility and Polycomb regulation, with site-specific H3K27me3 variations and transcriptional dysregulation of bivalent genes. We conclude that the correct assembly of lamina associated domains is functionally connected to the Polycomb repression and rapidly lost in early molecular events of progeria pathogenesis.
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Affiliation(s)
- Endre Sebestyén
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy
- 1st Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary
| | - Fabrizia Marullo
- Institute of Cell Biology and Neurobiology, National Research Council, Rome, Italy
| | - Federica Lucini
- Istituto Nazionale Genetica Molecolare "Romeo ed Enrica Invernizzi", Milan, Italy
| | | | - Andrea Bianchi
- Institute of Cell Biology and Neurobiology, National Research Council, Rome, Italy
- IRCCS Santa Lucia Foundation, Rome, Italy
| | - Sara Valsoni
- IRCCS Santa Lucia Foundation, Rome, Italy
- Institute for High Performance Computing and Networking, National Research Council, Naples, Italy
| | - Ilaria Olivieri
- Institute of Cell Biology and Neurobiology, National Research Council, Rome, Italy
| | - Laura Antonelli
- Institute for High Performance Computing and Networking, National Research Council, Naples, Italy
| | - Francesco Gregoretti
- Institute for High Performance Computing and Networking, National Research Council, Naples, Italy
| | - Gennaro Oliva
- Institute for High Performance Computing and Networking, National Research Council, Naples, Italy
| | - Francesco Ferrari
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy.
- Institute of Molecular Genetics, National Research Council, Pavia, Italy.
| | - Chiara Lanzuolo
- Istituto Nazionale Genetica Molecolare "Romeo ed Enrica Invernizzi", Milan, Italy.
- Institute of Biomedical Technologies, National Research Council, Milan, Italy.
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5
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Trotta E. RNA polymerase II (RNAP II)-associated factors are recruited to tRNA loci, revealing that RNAP II- and RNAP III-mediated transcriptions overlap in yeast. J Biol Chem 2019; 294:12349-12358. [PMID: 31235518 PMCID: PMC6699833 DOI: 10.1074/jbc.ra119.008529] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 06/19/2019] [Indexed: 07/24/2023] Open
Abstract
In yeast (Saccharomyces cerevisiae), the synthesis of tRNAs by RNA polymerase III (RNAP III) down-regulates the transcription of the nearby RNAP II-transcribed genes by a mechanism that is poorly understood. To clarify the basis of this tRNA gene-mediated (TGM) silencing, here, conducting a bioinformatics analysis of available ChIP-chip and ChIP-sequencing genomic data from yeast, we investigated whether the RNAP III transcriptional machinery can recruit protein factors required for RNAP II transcription. An analysis of 46 genome-wide protein-density profiles revealed that 12 factors normally implicated in RNAP II-mediated gene transcription are more enriched at tRNA than at mRNA loci. These 12 factors typically have RNA-binding properties, participate in the termination stage of the RNAP II transcription, and preferentially localize to the tRNA loci by a mechanism that apparently is based on the RNAP III transcription level. The factors included two kinases of RNAP II (Bur1 and Ctk1), a histone demethylase (Jhd2), and a mutated form of a nucleosome-remodeling factor (Spt6) that have never been reported to be recruited to tRNA loci. Moreover, we show that the expression levels of RNAP II-transcribed genes downstream of tRNA loci correlate with the distance from the tRNA gene by a mechanism that depends on their orientation. These results are consistent with the notion that pre-tRNAs recruit RNAP II-associated factors, thereby reducing the availability of these factors for RNAP II transcription and contributing, at least in part, to the TGM-silencing mechanism.
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Affiliation(s)
- Edoardo Trotta
- Institute of Translational Pharmacology, Consiglio Nazionale delle Ricerche (CNR), Roma 00133, Italy.
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6
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Caballero CJ, Menendez-Gil P, Catalan-Moreno A, Vergara-Irigaray M, García B, Segura V, Irurzun N, Villanueva M, Ruiz de Los Mozos I, Solano C, Lasa I, Toledo-Arana A. The regulon of the RNA chaperone CspA and its auto-regulation in Staphylococcus aureus. Nucleic Acids Res 2019; 46:1345-1361. [PMID: 29309682 PMCID: PMC5815144 DOI: 10.1093/nar/gkx1284] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 12/18/2017] [Indexed: 12/21/2022] Open
Abstract
RNA-binding proteins (RBPs) are essential to fine-tune gene expression. RBPs containing the cold-shock domain are RNA chaperones that have been extensively studied. However, the RNA targets and specific functions for many of them remain elusive. Here, combining comparative proteomics and RBP-immunoprecipitation-microarray profiling, we have determined the regulon of the RNA chaperone CspA of Staphylococcus aureus. Functional analysis revealed that proteins involved in carbohydrate and ribonucleotide metabolism, stress response and virulence gene expression were affected by cspA deletion. Stress-associated phenotypes such as increased bacterial aggregation and diminished resistance to oxidative-stress stood out. Integration of the proteome and targetome showed that CspA post-transcriptionally modulates both positively and negatively the expression of its targets, denoting additional functions to the previously proposed translation enhancement. One of these repressed targets was its own mRNA, indicating the presence of a negative post-transcriptional feedback loop. CspA bound the 5′UTR of its own mRNA disrupting a hairpin, which was previously described as an RNase III target. Thus, deletion of the cspA 5′UTR abrogated mRNA processing and auto-regulation. We propose that CspA interacts through a U-rich motif, which is located at the RNase III cleavage site, portraying CspA as a putative RNase III-antagonist.
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Affiliation(s)
- Carlos J Caballero
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain
| | - Pilar Menendez-Gil
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain
| | - Arancha Catalan-Moreno
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain
| | - Marta Vergara-Irigaray
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain.,Navarrabiomed-Universidad Pública de Navarra (UPNA)-Complejo Hospitalario de Navarra (CHN), IDISNA. 31008 Pamplona, Navarra, Spain
| | - Begoña García
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain.,Navarrabiomed-Universidad Pública de Navarra (UPNA)-Complejo Hospitalario de Navarra (CHN), IDISNA. 31008 Pamplona, Navarra, Spain
| | - Víctor Segura
- Genomics, Proteomics and Bioinformatics Unit. Center for Applied Medical Research. University of Navarra. 31008 Pamplona, Spain
| | - Naiara Irurzun
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain
| | - Maite Villanueva
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain
| | - Igor Ruiz de Los Mozos
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain
| | - Cristina Solano
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain.,Navarrabiomed-Universidad Pública de Navarra (UPNA)-Complejo Hospitalario de Navarra (CHN), IDISNA. 31008 Pamplona, Navarra, Spain
| | - Iñigo Lasa
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain.,Navarrabiomed-Universidad Pública de Navarra (UPNA)-Complejo Hospitalario de Navarra (CHN), IDISNA. 31008 Pamplona, Navarra, Spain
| | - Alejandro Toledo-Arana
- Instituto de Agrobiotecnología. IDAB, CSIC-UPNA-Gobierno de Navarra. 31192-Mutilva, Navarra, Spain
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7
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McIntosh M, Serrania J, Lacanna E. A novel LuxR-type solo of Sinorhizobium meliloti, NurR, is regulated by the chromosome replication coordinator, DnaA and activates quorum sensing. Mol Microbiol 2019; 112:678-698. [PMID: 31124196 DOI: 10.1111/mmi.14312] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2019] [Indexed: 12/16/2022]
Abstract
The genome of Sinorhizobium meliloti, a model for studying plant-bacteria symbiosis, contains eight genes coding for LuxR-like proteins. Two of these, SinR and ExpR, are essential for quorum sensing (QS). Roles and regulation surrounding the others are mostly unknown. Here, we reveal the DNA recognition sequence and regulon of the LuxR-like protein SMc00877. Unlike ExpR, which uses the long-chain acyl homoserine lactones (AHLs) as inducers, SMc00877 functioned independently of AHLs and was even functional in Escherichia coli. A target of SMc00877 is SinR, the major regulator of AHL production in S. meliloti. Disruption of SMc00877 decreased AHL production. A weaker production of AHLs resulted in smaller microcolonies, starting from single cells, and delayed AHL-dependent regulation. SMc00877 was expressed only in growing cells in the presence of replete nutrients. Therefore, we renamed it NurR (nutrient sensitive LuxR-like regulator). We traced this nutrient-sensitive expression to transcription control by the DNA replication initiation factor, DnaA, which is essential for growth. These results indicate that NurR has a role in modulating the threshold of QS activation according to growth. We propose growth behavior as an additional prerequisite to population density for the activation of QS in S. meliloti.
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Affiliation(s)
- Matthew McIntosh
- LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, Marburg, 35043, Germany.,Faculty of Biology, Philipps-Universität Marburg, Marburg, 35043, Germany.,Institut für Mikrobiologie und Molekularbiologie, Universität Giessen, Heinrich-Buff-Ring 26-32, Giessen, 35392, Germany
| | - Javier Serrania
- LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, Marburg, 35043, Germany.,Faculty of Biology, Philipps-Universität Marburg, Marburg, 35043, Germany
| | - Egidio Lacanna
- LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, Marburg, 35043, Germany.,Faculty of Biology, Philipps-Universität Marburg, Marburg, 35043, Germany
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8
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In Vivo and In Vitro Assay for Monitoring the Topological Loading of Bacterial Condensins on DNA. Methods Mol Biol 2019. [PMID: 31147918 DOI: 10.1007/978-1-4939-9520-2_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Condensins play essential roles in the compaction and segregation of chromosomal DNA in life forms ranging from bacteria to higher organisms. To elucidate the molecular mechanisms underlying these roles, it is crucial to determine how and where condensins are loaded to chromosomal DNA. Here, we describe in vivo and in vitro assays for monitoring the topological loading of two bacterial condensins, Smc-ScpAB and MukBEF. A key step in these assays is washing the samples with a high concentration of salt in order to discriminate between electrostatic and topological binding of the bacterial condensins to DNA. In addition, isolation of bacterial condensin and DNA complexes prevents any undesired interaction between them due to cross-linking reagents. These methodologies provide reproducible and reliable results for the loading of topologically bound proteins such as bacterial condensins.
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9
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Datta V, Hannenhalli S, Siddharthan R. ChIPulate: A comprehensive ChIP-seq simulation pipeline. PLoS Comput Biol 2019; 15:e1006921. [PMID: 30897079 PMCID: PMC6445533 DOI: 10.1371/journal.pcbi.1006921] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 04/02/2019] [Accepted: 03/04/2019] [Indexed: 12/17/2022] Open
Abstract
ChIP-seq (Chromatin Immunoprecipitation followed by sequencing) is a high-throughput technique to identify genomic regions that are bound in vivo by a particular protein, e.g., a transcription factor (TF). Biological factors, such as chromatin state, indirect and cooperative binding, as well as experimental factors, such as antibody quality, cross-linking, and PCR biases, are known to affect the outcome of ChIP-seq experiments. However, the relative impact of these factors on inferences made from ChIP-seq data is not entirely clear. Here, via a detailed ChIP-seq simulation pipeline, ChIPulate, we assess the impact of various biological and experimental sources of variation on several outcomes of a ChIP-seq experiment, viz., the recoverability of the TF binding motif, accuracy of TF-DNA binding detection, the sensitivity of inferred TF-DNA binding strength, and number of replicates needed to confidently infer binding strength. We find that the TF motif can be recovered despite poor and non-uniform extraction and PCR amplification efficiencies. The recovery of the motif is, however, affected to a larger extent by the fraction of sites that are either cooperatively or indirectly bound. Importantly, our simulations reveal that the number of ChIP-seq replicates needed to accurately measure in vivo occupancy at high-affinity sites is larger than the recommended community standards. Our results establish statistical limits on the accuracy of inferences of protein-DNA binding from ChIP-seq and suggest that increasing the mean extraction efficiency, rather than amplification efficiency, would better improve sensitivity. The source code and instructions for running ChIPulate can be found at https://github.com/vishakad/chipulate. DNA-binding proteins perform many key roles in biology, such as transcriptional regulation of gene expression and chromatin modification. ChIP-seq (Chromatin immunoprecipitation followed by high-throughput sequencing) is a widely used experimental technique to identify DNA-binding sites of specific proteins of interest, within cells, genome-wide. DNA fragments from genomic regions that are bound by a protein of interest, often a transcription factor (TF), are selectively extracted using specific antibodies, amplified using PCR, and sequenced. The sequences are mapped to the reference genome. Regions where many sequences map, called “peaks”, are used to infer the location of TF-bound loci (peaks), in vivo occupancy at those loci, and the sequence pattern (motif) to which the TF shows a binding affinity. But measurements of TF occupancy and motif inference are vulnerable to several biological and experimental sources of variation that are poorly understood and difficult to assess directly. Here, we simulate key steps of the ChIP-seq protocol with the aim of estimating the relative effects of various sources of variations on motif inference and binding affinity estimations. Besides providing specific insights and recommendations, we provide a general framework to simulate sequence reads in a ChIP-seq experiment, which should considerably aid in the development of software aimed at analyzing ChIP-seq data.
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Affiliation(s)
- Vishaka Datta
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, TIFR, Bengaluru, Karnataka, India
- * E-mail:
| | - Sridhar Hannenhalli
- Center for Bioinformatics and Computational Biology, University of Maryland, College Park, Maryland, United States of America
| | - Rahul Siddharthan
- The Institute of Mathematical Sciences/HBNI, Taramani, Chennai, India
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10
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Santos-Zavaleta A, Sánchez-Pérez M, Salgado H, Velázquez-Ramírez DA, Gama-Castro S, Tierrafría VH, Busby SJW, Aquino P, Fang X, Palsson BO, Galagan JE, Collado-Vides J. A unified resource for transcriptional regulation in Escherichia coli K-12 incorporating high-throughput-generated binding data into RegulonDB version 10.0. BMC Biol 2018; 16:91. [PMID: 30115066 PMCID: PMC6094552 DOI: 10.1186/s12915-018-0555-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 07/25/2018] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Our understanding of the regulation of gene expression has benefited from the availability of high-throughput technologies that interrogate the whole genome for the binding of specific transcription factors and gene expression profiles. In the case of widely used model organisms, such as Escherichia coli K-12, the new knowledge gained from these approaches needs to be integrated with the legacy of accumulated knowledge from genetic and molecular biology experiments conducted in the pre-genomic era in order to attain the deepest level of understanding possible based on the available data. RESULTS In this paper, we describe an expansion of RegulonDB, the database containing the rich legacy of decades of classic molecular biology experiments supporting what we know about gene regulation and operon organization in E. coli K-12, to include the genome-wide dataset collections from 32 ChIP and 19 gSELEX publications, in addition to around 60 genome-wide expression profiles relevant to the functional significance of these datasets and used in their curation. Three essential features for the integration of this information coming from different methodological approaches are: first, a controlled vocabulary within an ontology for precisely defining growth conditions; second, the criteria to separate elements with enough evidence to consider them involved in gene regulation from isolated transcription factor binding sites without such support; and third, an expanded computational model supporting this knowledge. Altogether, this constitutes the basis for adequately gathering and enabling the comparisons and integration needed to manage and access such wealth of knowledge. CONCLUSIONS This version 10.0 of RegulonDB is a first step toward what should become the unifying access point for current and future knowledge on gene regulation in E. coli K-12. Furthermore, this model platform and associated methodologies and criteria can be emulated for gathering knowledge on other microbial organisms.
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Affiliation(s)
- Alberto Santos-Zavaleta
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos México
| | - Mishael Sánchez-Pérez
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos México
| | - Heladia Salgado
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos México
| | | | - Socorro Gama-Castro
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos México
| | - Víctor H. Tierrafría
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos México
| | | | - Patricia Aquino
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts USA
| | - Xin Fang
- Department of Bioengineering, University of California San Diego, La Jolla, California USA
| | - Bernhard O. Palsson
- Department of Bioengineering, University of California San Diego, La Jolla, California USA
- Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
| | - James E. Galagan
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts USA
| | - Julio Collado-Vides
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos México
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts USA
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11
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Phenotypes of dnaXE145A Mutant Cells Indicate that the Escherichia coli Clamp Loader Has a Role in the Restart of Stalled Replication Forks. J Bacteriol 2017; 199:JB.00412-17. [PMID: 28947673 DOI: 10.1128/jb.00412-17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 09/18/2017] [Indexed: 12/27/2022] Open
Abstract
The Escherichia colidnaXE145A mutation was discovered in connection with a screen for multicopy suppressors of the temperature-sensitive topoisomerase IV mutation parE10 The gene for the clamp loader subunits τ and γ, dnaX, but not the mutant dnaXE145A , was found to suppress parE10(Ts) when overexpressed. Purified mutant protein was found to be functional in vitro, and few phenotypes were found in vivo apart from problems with partitioning of DNA in rich medium. We show here that a large number of the replication forks that initiate at oriC never reach the terminus in dnaXE145A mutant cells. The SOS response was found to be induced, and a combination of the dnaXE145A mutation with recBC and recA mutations led to reduced viability. The mutant cells exhibited extensive chromosome fragmentation and degradation upon inactivation of recBC and recA, respectively. The results indicate that the dnaXE145A mutant cells suffer from broken replication forks and that these need to be repaired by homologous recombination. We suggest that the dnaX-encoded τ and γ subunits of the clamp loader, or the clamp loader complex itself, has a role in the restart of stalled replication forks without extensive homologous recombination.IMPORTANCE The E. coli clamp loader complex has a role in coordinating the activity of the replisome at the replication fork and loading β-clamps for lagging-strand synthesis. Replication forks frequently encounter obstacles, such as template lesions, secondary structures, and tightly bound protein complexes, which will lead to fork stalling. Some pathways of fork restart have been characterized, but much is still unknown about the actors and mechanisms involved. We have in this work characterized the dnaXE145A clamp loader mutant. We find that the naturally occurring obstacles encountered by a replication fork are not tackled in a proper way by the mutant clamp loader and suggest a role for the clamp loader in the restart of stalled replication forks.
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12
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Yoganand KNR, Sivathanu R, Nimkar S, Anand B. Asymmetric positioning of Cas1-2 complex and Integration Host Factor induced DNA bending guide the unidirectional homing of protospacer in CRISPR-Cas type I-E system. Nucleic Acids Res 2016; 45:367-381. [PMID: 27899566 PMCID: PMC5224486 DOI: 10.1093/nar/gkw1151] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 11/01/2016] [Accepted: 11/03/2016] [Indexed: 01/21/2023] Open
Abstract
CRISPR-Cas system epitomizes prokaryote-specific quintessential adaptive defense machinery that limits the genome invasion of mobile genetic elements. It confers adaptive immunity to bacteria by capturing a protospacer fragment from invading foreign DNA, which is later inserted into the leader proximal end of CRIPSR array and serves as immunological memory to recognize recurrent invasions. The universally conserved Cas1 and Cas2 form an integration complex that is known to mediate the protospacer invasion into the CRISPR array. However, the mechanism by which this protospacer fragment gets integrated in a directional fashion into the leader proximal end is elusive. Here, we employ CRISPR/dCas9 mediated immunoprecipitation and genetic analysis to identify Integration Host Factor (IHF) as an indispensable accessory factor for spacer acquisition in Escherichia coli Further, we show that the leader region abutting the first CRISPR repeat localizes IHF and Cas1-2 complex. IHF binding to the leader region induces bending by about 120° that in turn engenders the regeneration of the cognate binding site for protospacer bound Cas1-2 complex and brings it in proximity with the first CRISPR repeat. This appears to guide Cas1-2 complex to orient the protospacer invasion towards the leader-repeat junction thus driving the integration in a polarized fashion.
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Affiliation(s)
- K N R Yoganand
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - R Sivathanu
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Siddharth Nimkar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - B Anand
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
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13
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Waardenberg AJ, Homan B, Mohamed S, Harvey RP, Bouveret R. Prediction and validation of protein-protein interactors from genome-wide DNA-binding data using a knowledge-based machine-learning approach. Open Biol 2016; 6:rsob.160183. [PMID: 27683156 PMCID: PMC5043580 DOI: 10.1098/rsob.160183] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/05/2016] [Indexed: 01/14/2023] Open
Abstract
The ability to accurately predict the DNA targets and interacting cofactors of transcriptional regulators from genome-wide data can significantly advance our understanding of gene regulatory networks. NKX2-5 is a homeodomain transcription factor that sits high in the cardiac gene regulatory network and is essential for normal heart development. We previously identified genomic targets for NKX2-5 in mouse HL-1 atrial cardiomyocytes using DNA-adenine methyltransferase identification (DamID). Here, we apply machine learning algorithms and propose a knowledge-based feature selection method for predicting NKX2-5 protein : protein interactions based on motif grammar in genome-wide DNA-binding data. We assessed model performance using leave-one-out cross-validation and a completely independent DamID experiment performed with replicates. In addition to identifying previously described NKX2-5-interacting proteins, including GATA, HAND and TBX family members, a number of novel interactors were identified, with direct protein : protein interactions between NKX2-5 and retinoid X receptor (RXR), paired-related homeobox (PRRX) and Ikaros zinc fingers (IKZF) validated using the yeast two-hybrid assay. We also found that the interaction of RXRα with NKX2-5 mutations found in congenital heart disease (Q187H, R189G and R190H) was altered. These findings highlight an intuitive approach to accessing protein-protein interaction information of transcription factors in DNA-binding experiments.
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Affiliation(s)
- Ashley J Waardenberg
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia Children's Medical Research Institute, University of Sydney, Westmead, New South Wales 2145, Australia
| | - Bernou Homan
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Stephanie Mohamed
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Richard P Harvey
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia St Vincent's Clinical School, University of Sydney, Westmead, New South Wales 2145, Australia School of Biotechnology and Biomolecular Science, University of New South Wales, Kensington, New South Wales 2052, Australia
| | - Romaric Bouveret
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia St Vincent's Clinical School, University of Sydney, Westmead, New South Wales 2145, Australia
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14
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Adhikari S, Curtis PD. DNA methyltransferases and epigenetic regulation in bacteria. FEMS Microbiol Rev 2016; 40:575-91. [PMID: 27476077 DOI: 10.1093/femsre/fuw023] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/30/2016] [Indexed: 12/21/2022] Open
Abstract
Epigenetics is a change in gene expression that is heritable without a change in DNA sequence itself. This phenomenon is well studied in eukaryotes, particularly in humans for its role in cellular differentiation, X chromosome inactivation and diseases like cancer. However, comparatively little is known about epigenetic regulation in bacteria. Bacterial epigenetics is mainly present in the form of DNA methylation where DNA methyltransferases add methyl groups to nucleotides. This review focuses on two methyltransferases well characterized for their roles in gene regulation: Dam and CcrM. Dam methyltransferase in Escherichia coli is important for expression of certain genes such as the pap operon, as well as other cellular processes like DNA replication initiation and DNA repair. In Caulobacter crescentus and other Alphaproteobacteria, the methyltransferase CcrM is cell cycle regulated and is involved in the cell-cycle-dependent regulation of several genes. The diversity of regulatory targets as well as regulatory mechanisms suggests that gene regulation by methylation could be a widespread and potent method of regulation in bacteria.
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Affiliation(s)
- Satish Adhikari
- Department of Biology, University of Mississippi, University, MS 38677, USA
| | - Patrick D Curtis
- Department of Biology, University of Mississippi, University, MS 38677, USA
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15
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Haycocks JRJ, Grainger DC. Unusually Situated Binding Sites for Bacterial Transcription Factors Can Have Hidden Functionality. PLoS One 2016; 11:e0157016. [PMID: 27258043 PMCID: PMC4892627 DOI: 10.1371/journal.pone.0157016] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 05/23/2016] [Indexed: 01/13/2023] Open
Abstract
A commonly accepted paradigm of molecular biology is that transcription factors control gene expression by binding sites at the 5' end of a gene. However, there is growing evidence that transcription factor targets can occur within genes or between convergent genes. In this work, we have investigated one such target for the cyclic AMP receptor protein (CRP) of enterotoxigenic Escherichia coli. We show that CRP binds between two convergent genes. When bound, CRP regulates transcription of a small open reading frame, which we term aatS, embedded within one of the adjacent genes. Our work demonstrates that non-canonical sites of transcription factor binding can have hidden functionality.
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Affiliation(s)
- James R. J. Haycocks
- Institute of Microbiology and Infection, School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - David C. Grainger
- Institute of Microbiology and Infection, School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- * E-mail:
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16
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Multiplex enhancer-reporter assays uncover unsophisticated TP53 enhancer logic. Genome Res 2016; 26:882-95. [PMID: 27197205 PMCID: PMC4937571 DOI: 10.1101/gr.204149.116] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 05/17/2016] [Indexed: 12/11/2022]
Abstract
Transcription factors regulate their target genes by binding to regulatory regions in the genome. Although the binding preferences of TP53 are known, it remains unclear what distinguishes functional enhancers from nonfunctional binding. In addition, the genome is scattered with recognition sequences that remain unoccupied. Using two complementary techniques of multiplex enhancer-reporter assays, we discovered that functional enhancers could be discriminated from nonfunctional binding events by the occurrence of a single TP53 canonical motif. By combining machine learning with a meta-analysis of TP53 ChIP-seq data sets, we identified a core set of more than 1000 responsive enhancers in the human genome. This TP53 cistrome is invariably used between cell types and experimental conditions, whereas differences among experiments can be attributed to indirect nonfunctional binding events. Our data suggest that TP53 enhancers represent a class of unsophisticated cell-autonomous enhancers containing a single TP53 binding site, distinct from complex developmental enhancers that integrate signals from multiple transcription factors.
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17
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FabR regulates Salmonella biofilm formation via its direct target FabB. BMC Genomics 2016; 17:253. [PMID: 27004424 PMCID: PMC4804515 DOI: 10.1186/s12864-016-2387-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 01/08/2016] [Indexed: 12/02/2022] Open
Abstract
Background Biofilm formation is an important survival strategy of Salmonella in all environments. By mutant screening, we showed a knock-out mutant of fabR, encoding a repressor of unsaturated fatty acid biosynthesis (UFA), to have impaired biofilm formation. In order to unravel how this regulator impinges on Salmonella biofilm formation, we aimed at elucidating the S. Typhimurium FabR regulon. Hereto, we applied a combinatorial high-throughput approach, combining ChIP-chip with transcriptomics. Results All the previously identified E. coli FabR transcriptional target genes (fabA, fabB and yqfA) were shown to be direct S. Typhimurium FabR targets as well. As we found a fabB overexpressing strain to partly mimic the biofilm defect of the fabR mutant, the effect of FabR on biofilms can be attributed at least partly to FabB, which plays a key role in UFA biosynthesis. Additionally, ChIP-chip identified a number of novel direct FabR targets (the intergenic regions between hpaR/hpaG and ddg/ydfZ) and yet putative direct targets (i.a. genes involved in tRNA metabolism, ribosome synthesis and translation). Next to UFA biosynthesis, a number of these direct targets and other indirect targets identified by transcriptomics (e.g. ribosomal genes, ompA, ompC, ompX, osmB, osmC, sseI), could possibly contribute to the effect of FabR on biofilm formation. Conclusion Overall, our results point at the importance of FabR and UFA biosynthesis in Salmonella biofilm formation and their role as potential targets for biofilm inhibitory strategies. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2387-x) contains supplementary material, which is available to authorized users.
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Sobetzko P, Jelonek L, Strickert M, Han W, Goesmann A, Waldminghaus T. DistAMo: A Web-Based Tool to Characterize DNA-Motif Distribution on Bacterial Chromosomes. Front Microbiol 2016; 7:283. [PMID: 27014208 PMCID: PMC4786541 DOI: 10.3389/fmicb.2016.00283] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 02/22/2016] [Indexed: 01/10/2023] Open
Abstract
Short DNA motifs are involved in a multitude of functions such as for example chromosome segregation, DNA replication or mismatch repair. Distribution of such motifs is often not random and the specific chromosomal pattern relates to the respective motif function. Computational approaches which quantitatively assess such chromosomal motif patterns are necessary. Here we present a new computer tool DistAMo (Distribution Analysis of DNA Motifs). The algorithm uses codon redundancy to calculate the relative abundance of short DNA motifs from single genes to entire chromosomes. Comparative genomics analyses of the GATC-motif distribution in γ-proteobacterial genomes using DistAMo revealed that (i) genes beside the replication origin are enriched in GATCs, (ii) genome-wide GATC distribution follows a distinct pattern, and (iii) genes involved in DNA replication and repair are enriched in GATCs. These features are specific for bacterial chromosomes encoding a Dam methyltransferase. The new software is available as a stand-alone or as an easy-to-use web-based server version at http://www.computational.bio.uni-giessen.de/distamo.
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Affiliation(s)
- Patrick Sobetzko
- Chromosome Biology Group, LOEWE Center for Synthetic Microbiology, SYNMIKRO, Philipps-University Marburg Marburg, Germany
| | - Lukas Jelonek
- Bioinformatics and Systems Biology, Faculty of Biology and Chemistry, Justus-Liebig-University Giessen, Germany
| | - Marc Strickert
- Chromosome Biology Group, LOEWE Center for Synthetic Microbiology, SYNMIKRO, Philipps-University Marburg Marburg, Germany
| | - Wenxia Han
- Chromosome Biology Group, LOEWE Center for Synthetic Microbiology, SYNMIKRO, Philipps-University Marburg Marburg, Germany
| | - Alexander Goesmann
- Bioinformatics and Systems Biology, Faculty of Biology and Chemistry, Justus-Liebig-University Giessen, Germany
| | - Torsten Waldminghaus
- Chromosome Biology Group, LOEWE Center for Synthetic Microbiology, SYNMIKRO, Philipps-University Marburg Marburg, Germany
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19
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Lobel L, Herskovits AA. Systems Level Analyses Reveal Multiple Regulatory Activities of CodY Controlling Metabolism, Motility and Virulence in Listeria monocytogenes. PLoS Genet 2016; 12:e1005870. [PMID: 26895237 PMCID: PMC4760761 DOI: 10.1371/journal.pgen.1005870] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 01/22/2016] [Indexed: 02/05/2023] Open
Abstract
Bacteria sense and respond to many environmental cues, rewiring their regulatory network to facilitate adaptation to new conditions/niches. Global transcription factors that co-regulate multiple pathways simultaneously are essential to this regulatory rewiring. CodY is one such global regulator, controlling expression of both metabolic and virulence genes in Gram-positive bacteria. Branch chained amino acids (BCAAs) serve as a ligand for CodY and modulate its activity. Classically, CodY was considered to function primarily as a repressor under rich growth conditions. However, our previous studies of the bacterial pathogen Listeria monocytogenes revealed that CodY is active also when the bacteria are starved for BCAAs. Under these conditions, CodY loses the ability to repress genes (e.g., metabolic genes) and functions as a direct activator of the master virulence regulator gene, prfA. This observation raised the possibility that CodY possesses multiple functions that allow it to coordinate gene expression across a wide spectrum of metabolic growth conditions, and thus better adapt bacteria to the mammalian niche. To gain a deeper understanding of CodY's regulatory repertoire and identify direct target genes, we performed a genome wide analysis of the CodY regulon and DNA binding under both rich and minimal growth conditions, using RNA-Seq and ChIP-Seq techniques. We demonstrate here that CodY is indeed active (i.e., binds DNA) under both conditions, serving as a repressor and activator of different genes. Further, we identified new genes and pathways that are directly regulated by CodY (e.g., sigB, arg, his, actA, glpF, gadG, gdhA, poxB, glnR and fla genes), integrating metabolism, stress responses, motility and virulence in L. monocytogenes. This study establishes CodY as a multifaceted factor regulating L. monocytogenes physiology in a highly versatile manner.
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Affiliation(s)
- Lior Lobel
- The Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Anat A. Herskovits
- The Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
- * E-mail:
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20
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Abstract
The DNA of Escherichia coli contains 19,120 6-methyladenines and 12,045 5-methylcytosines in addition to the four regular bases, and these are formed by the postreplicative action of three DNA methyltransferases. The majority of the methylated bases are formed by the Dam and Dcm methyltransferases encoded by the dam (DNA adenine methyltransferase) and dcm (DNA cytosine methyltransferase) genes. Although not essential, Dam methylation is important for strand discrimination during the repair of replication errors, controlling the frequency of initiation of chromosome replication at oriC, and the regulation of transcription initiation at promoters containing GATC sequences. In contrast, there is no known function for Dcm methylation, although Dcm recognition sites constitute sequence motifs for Very Short Patch repair of T/G base mismatches. In certain bacteria (e.g., Vibrio cholerae, Caulobacter crescentus) adenine methylation is essential, and, in C. crescentus, it is important for temporal gene expression, which, in turn, is required for coordinating chromosome initiation, replication, and division. In practical terms, Dam and Dcm methylation can inhibit restriction enzyme cleavage, decrease transformation frequency in certain bacteria, and decrease the stability of short direct repeats and are necessary for site-directed mutagenesis and to probe eukaryotic structure and function.
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21
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Bonocora RP, Smith C, Lapierre P, Wade JT. Genome-Scale Mapping of Escherichia coli σ54 Reveals Widespread, Conserved Intragenic Binding. PLoS Genet 2015; 11:e1005552. [PMID: 26425847 PMCID: PMC4591121 DOI: 10.1371/journal.pgen.1005552] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 09/03/2015] [Indexed: 11/18/2022] Open
Abstract
Bacterial RNA polymerases must associate with a σ factor to bind promoter DNA and initiate transcription. There are two families of σ factor: the σ70 family and the σ54 family. Members of the σ54 family are distinct in their ability to bind promoter DNA sequences, in the context of RNA polymerase holoenzyme, in a transcriptionally inactive state. Here, we map the genome-wide association of Escherichia coli σ54, the archetypal member of the σ54 family. Thus, we vastly expand the list of known σ54 binding sites to 135. Moreover, we estimate that there are more than 250 σ54 sites in total. Strikingly, the majority of σ54 binding sites are located inside genes. The location and orientation of intragenic σ54 binding sites is non-random, and many intragenic σ54 binding sites are conserved. We conclude that many intragenic σ54 binding sites are likely to be functional. Consistent with this assertion, we identify three conserved, intragenic σ54 promoters that drive transcription of mRNAs with unusually long 5ʹ UTRs. Bacterial RNA polymerases must associate with a σ factor to bind to promoter DNA sequences upstream of genes and initiate transcription. There are two families of σ factor: σ70 and σ54. Members of the σ54 family are distinct from members of the σ70 family in their ability to bind promoter DNA sequences, in association with RNA polymerase, in a transcriptionally inactive state. We have determined positions in the Escherichia coli genome that are bound by σ54, the archetypal member of the σ54 family. Surprisingly, we identified 135 binding sites for σ54, a huge increase over the number of previously described sites. Our data suggest that there are more than 250 σ54 sites in total. Strikingly, most σ54 binding sites are located inside genes, whereas only one intragenic σ54 binding site has previously been described. The location and orientation of intragenic σ54 binding sites is non-random, and many intragenic σ54 binding sites are conserved in other bacterial species. We conclude that many intragenic σ54 binding sites are likely to be functional. Consistent with this notion, we identify three σ54 promoters in E. coli that are located inside genes but drive transcription of unusual mRNAs for the neighboring genes.
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Affiliation(s)
- Richard P. Bonocora
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Carol Smith
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Pascal Lapierre
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Joseph T. Wade
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America
- * E-mail:
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22
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Quantitative genomic analysis of RecA protein binding during DNA double-strand break repair reveals RecBCD action in vivo. Proc Natl Acad Sci U S A 2015; 112:E4735-42. [PMID: 26261330 PMCID: PMC4553759 DOI: 10.1073/pnas.1424269112] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Understanding molecular mechanisms in the context of living cells requires the development of new methods of in vivo biochemical analysis to complement established in vitro biochemistry. A critically important molecular mechanism is genetic recombination, required for the beneficial reassortment of genetic information and for DNA double-strand break repair (DSBR). Central to recombination is the RecA (Rad51) protein that assembles into a spiral filament on DNA and mediates genetic exchange. Here we have developed a method that combines chromatin immunoprecipitation with next-generation sequencing (ChIP-Seq) and mathematical modeling to quantify RecA protein binding during the active repair of a single DSB in the chromosome of Escherichia coli. We have used quantitative genomic analysis to infer the key in vivo molecular parameters governing RecA loading by the helicase/nuclease RecBCD at recombination hot-spots, known as Chi. Our genomic analysis has also revealed that DSBR at the lacZ locus causes a second RecBCD-mediated DSBR event to occur in the terminus region of the chromosome, over 1 Mb away.
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23
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Bouveret R, Waardenberg AJ, Schonrock N, Ramialison M, Doan T, de Jong D, Bondue A, Kaur G, Mohamed S, Fonoudi H, Chen CM, Wouters MA, Bhattacharya S, Plachta N, Dunwoodie SL, Chapman G, Blanpain C, Harvey RP. NKX2-5 mutations causative for congenital heart disease retain functionality and are directed to hundreds of targets. eLife 2015; 4. [PMID: 26146939 PMCID: PMC4548209 DOI: 10.7554/elife.06942] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 07/05/2015] [Indexed: 12/30/2022] Open
Abstract
We take a functional genomics approach to congenital heart disease mechanism. We used DamID to establish a robust set of target genes for NKX2-5 wild type and disease associated NKX2-5 mutations to model loss-of-function in gene regulatory networks. NKX2-5 mutants, including those with a crippled homeodomain, bound hundreds of targets including NKX2-5 wild type targets and a unique set of "off-targets", and retained partial functionality. NKXΔHD, which lacks the homeodomain completely, could heterodimerize with NKX2-5 wild type and its cofactors, including E26 transformation-specific (ETS) family members, through a tyrosine-rich homophilic interaction domain (YRD). Off-targets of NKX2-5 mutants, but not those of an NKX2-5 YRD mutant, showed overrepresentation of ETS binding sites and were occupied by ETS proteins, as determined by DamID. Analysis of kernel transcription factor and ETS targets show that ETS proteins are highly embedded within the cardiac gene regulatory network. Our study reveals binding and activities of NKX2-5 mutations on WT target and off-targets, guided by interactions with their normal cardiac and general cofactors, and suggest a novel type of gain-of-function in congenital heart disease.
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Affiliation(s)
- Romaric Bouveret
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | | | - Nicole Schonrock
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | | | - Tram Doan
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Danielle de Jong
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Antoine Bondue
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Université Libre de Bruxelles, Brussels, Belgium
| | - Gurpreet Kaur
- European Molecular Biology Laboratory, Australian Regenerative Medicine Institute, Monash University, Clayton, Australia
| | | | - Hananeh Fonoudi
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Chiann-Mun Chen
- Department of Cardiovascular Medicine, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Merridee A Wouters
- Bioinformatics, Olivia Newton-John Cancer Research Institute, Melbourne, Australia
| | - Shoumo Bhattacharya
- Department of Cardiovascular Medicine, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Nicolas Plachta
- European Molecular Biology Laboratory, Australian Regenerative Medicine Institute, Monash University, Clayton, Australia
| | | | - Gavin Chapman
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Cédric Blanpain
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Université Libre de Bruxelles, Brussels, Belgium
| | - Richard P Harvey
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
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24
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Jain D, Baldi S, Zabel A, Straub T, Becker PB. Active promoters give rise to false positive 'Phantom Peaks' in ChIP-seq experiments. Nucleic Acids Res 2015; 43:6959-68. [PMID: 26117547 PMCID: PMC4538825 DOI: 10.1093/nar/gkv637] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 06/08/2015] [Indexed: 02/07/2023] Open
Abstract
Chromatin immunoprecipitation (ChIP) is widely used to identify chromosomal binding sites. Chromatin proteins are cross-linked to their target sequences in living cells. The purified chromatin is sheared and the relevant protein is enriched by immunoprecipitation with specific antibodies. The co-purifying genomic DNA is then determined by massive parallel sequencing (ChIP-seq). We applied ChIP-seq to map the chromosomal binding sites for two ISWI-containing nucleosome remodeling factors, ACF and RSF, in Drosophila embryos. Employing several polyclonal and monoclonal antibodies directed against their signature subunits, ACF1 and RSF-1, robust profiles were obtained indicating that both remodelers co-occupied a large set of active promoters. Further validation included controls using chromatin of mutant embryos that do not express ACF1 or RSF-1. Surprisingly, the ChIP-seq profiles were unchanged, suggesting that they were not due to specific immunoprecipitation. Conservative analysis lists about 3000 chromosomal loci, mostly active promoters that are prone to non-specific enrichment in ChIP and appear as ‘Phantom Peaks’. These peaks are not obtained with pre-immune serum and are not prominent in input chromatin. Mining the modENCODE ChIP-seq profiles identifies potential Phantom Peaks in many profiles of epigenetic regulators. These profiles and other ChIP-seq data featuring prominent Phantom Peaks must be validated with chromatin from cells in which the protein of interest has been depleted.
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Affiliation(s)
- Dhawal Jain
- Biomedical Center and Center for Integrated Protein Science Munich, Ludwig-Maximilians-University, Munich, Germany
| | - Sandro Baldi
- Biomedical Center and Center for Integrated Protein Science Munich, Ludwig-Maximilians-University, Munich, Germany
| | - Angelika Zabel
- Biomedical Center and Center for Integrated Protein Science Munich, Ludwig-Maximilians-University, Munich, Germany
| | - Tobias Straub
- Biomedical Center and Center for Integrated Protein Science Munich, Ludwig-Maximilians-University, Munich, Germany
| | - Peter B Becker
- Biomedical Center and Center for Integrated Protein Science Munich, Ludwig-Maximilians-University, Munich, Germany
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Schindler D, Waldminghaus T. Synthetic chromosomes. FEMS Microbiol Rev 2015; 39:871-91. [DOI: 10.1093/femsre/fuv030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2015] [Indexed: 12/22/2022] Open
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Merrikh CN, Brewer BJ, Merrikh H. The B. subtilis Accessory Helicase PcrA Facilitates DNA Replication through Transcription Units. PLoS Genet 2015; 11:e1005289. [PMID: 26070154 PMCID: PMC4466434 DOI: 10.1371/journal.pgen.1005289] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 05/18/2015] [Indexed: 11/18/2022] Open
Abstract
In bacteria the concurrence of DNA replication and transcription leads to potentially deleterious encounters between the two machineries, which can occur in either the head-on (lagging strand genes) or co-directional (leading strand genes) orientations. These conflicts lead to replication fork stalling and can destabilize the genome. Both eukaryotic and prokaryotic cells possess resolution factors that reduce the severity of these encounters. Though Escherichia coli accessory helicases have been implicated in the mitigation of head-on conflicts, direct evidence of these proteins mitigating co-directional conflicts is lacking. Furthermore, the endogenous chromosomal regions where these helicases act, and the mechanism of recruitment, have not been identified. We show that the essential Bacillus subtilis accessory helicase PcrA aids replication progression through protein coding genes of both head-on and co-directional orientations, as well as rRNA and tRNA genes. ChIP-Seq experiments show that co-directional conflicts at highly transcribed rRNA, tRNA, and head-on protein coding genes are major targets of PcrA activity on the chromosome. Partial depletion of PcrA renders cells extremely sensitive to head-on conflicts, linking the essential function of PcrA to conflict resolution. Furthermore, ablating PcrA’s ATPase/helicase activity simultaneously increases its association with conflict regions, while incapacitating its ability to mitigate conflicts, and leads to cell death. In contrast, disruption of PcrA’s C-terminal RNA polymerase interaction domain does not impact its ability to mitigate conflicts between replication and transcription, its association with conflict regions, or cell survival. Altogether, this work establishes PcrA as an essential factor involved in mitigating transcription-replication conflicts and identifies chromosomal regions where it routinely acts. As both conflicts and accessory helicases are found in all domains of life, these results are broadly relevant. In bacteria the concurrence of DNA replication and transcription leads to potentially deleterious encounters between the two machineries. These encounters can destabilize the genome and lead to mutations. Both eukaryotic and prokaryotic cells possess conflict resolution factors that reduce the detrimental effects of these collisions. In this study we show that without the essential Bacillus subtilis accessory DNA helicase, PcrA, the replication machinery slows down at certain regions of the chromosome in a transcription-dependent manner. PcrA is essential to life but incomplete depletion of PcrA only partially inhibits cell survival. We find that, under these conditions, partial survival defects are significantly exacerbated in the presence of a single severe conflict. In summary our work identifies a high degree of conservation for accessory helicase function in conflict resolution, directly establishes PcrA’s role in co-directional conflict resolution, and maps the natural chromosomal regions where such activities are routinely needed. Because both conflicts and accessory helicases are found in all domains of life, the results of this work are broadly relevant.
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Affiliation(s)
- Christopher N. Merrikh
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
| | - Bonita J. Brewer
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Houra Merrikh
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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Flåtten I, Fossum-Raunehaug S, Taipale R, Martinsen S, Skarstad K. The DnaA Protein Is Not the Limiting Factor for Initiation of Replication in Escherichia coli. PLoS Genet 2015; 11:e1005276. [PMID: 26047361 PMCID: PMC4457925 DOI: 10.1371/journal.pgen.1005276] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 05/14/2015] [Indexed: 11/29/2022] Open
Abstract
The bacterial replication cycle is driven by the DnaA protein which cycles between the active ATP-bound form and the inactive ADP-bound form. It has been suggested that DnaA also is the main controller of initiation frequency. Initiation is thought to occur when enough ATP-DnaA has accumulated. In this work we have performed cell cycle analysis of cells that contain a surplus of ATP-DnaA and asked whether initiation then occurs earlier. It does not. Cells with more than a 50% increase in the concentration of ATP-DnaA showed no changes in timing of replication. We suggest that although ATP-DnaA is the main actor in initiation of replication, its accumulation does not control the time of initiation. ATP-DnaA is the motor that drives the initiation process, but other factors will be required for the exact timing of initiation in response to the cell’s environment. We also investigated the in vivo roles of datA dependent DnaA inactivation (DDAH) and the DnaA-binding protein DiaA. Loss of DDAH affected the cell cycle machinery only during slow growth and made it sensitive to the concentration of DiaA protein. The result indicates that compromised cell cycle machines perform in a less robust manner. Cell cycle regulation of the bacterium Escherichia coli has been studied for many years, and its understanding is complicated by the fact that overlapping replication cycles occur during growth in rich media. Under such conditions cells initiate several copies of the chromosome. The active form of the CDC6-like DnaA protein is required for initiation of synchronous and well-timed replication cycles and is in a sense the motor of the cell cycle machine. It has long been debated whether it is the accumulation of enough ATP-DnaA that triggers initiation and determines the replication frequency. In this work we have constructed a strain where the “accumulation of ATP-DnaA triggers initiation” model could be tested. Our results indicate that this model requires some modification. We suggest that cell cycle regulation in E. coli has similarities to that of eukaryotes in that origins are “licensed” to initiate by a cell cycle motor and that the precise timing depends on other signaling.
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Affiliation(s)
- Ingvild Flåtten
- Department of Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Solveig Fossum-Raunehaug
- Department of Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Riikka Taipale
- Department of Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Silje Martinsen
- Department of Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Kirsten Skarstad
- Department of Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
- * E-mail:
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Darnell CL, Schmid AK. Systems biology approaches to defining transcription regulatory networks in halophilic archaea. Methods 2015; 86:102-14. [PMID: 25976837 DOI: 10.1016/j.ymeth.2015.04.034] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 04/27/2015] [Accepted: 04/28/2015] [Indexed: 12/31/2022] Open
Abstract
To survive complex and changing environmental conditions, microorganisms use gene regulatory networks (GRNs) composed of interacting regulatory transcription factors (TFs) to control the timing and magnitude of gene expression. Genome-wide datasets; such as transcriptomics and protein-DNA interactions; and experiments such as high throughput growth curves; facilitate the construction of GRNs and provide insight into TF interactions occurring under stress. Systems biology approaches integrate these datasets into models of GRN architecture as well as statistical and/or dynamical models to understand the function of networks occurring in cells. Previously, these types of studies have focused on traditional model organisms (e.g. Escherichia coli, yeast). However, recent advances in archaeal genetics and other tools have enabled a systems approach to understanding GRNs in these relatively less studied archaeal model organisms. In this report, we outline a systems biology workflow for generating and integrating data focusing on the TF regulator. We discuss experimental design, outline the process of data collection, and provide the tools required to produce high confidence regulons for the TFs of interest. We provide a case study as an example of this workflow, describing the construction of a GRN centered on multi-TF coordinate control of gene expression governing the oxidative stress response in the hypersaline-adapted archaeon Halobacterium salinarum.
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Affiliation(s)
| | - Amy K Schmid
- Biology Department, Duke University, Durham, NC 27708, USA; Center for Systems Biology, Duke University, Durham, NC 27708, USA.
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Messerschmidt SJ, Waldminghaus T. Dynamic Organization: Chromosome Domains in Escherichia coli. J Mol Microbiol Biotechnol 2015; 24:301-15. [DOI: 10.1159/000369098] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Pillai S, Chellappan SP. ChIP on chip and ChIP-Seq assays: genome-wide analysis of transcription factor binding and histone modifications. Methods Mol Biol 2015; 1288:447-72. [PMID: 25827896 DOI: 10.1007/978-1-4939-2474-5_26] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Deregulation of transcriptional activity of many genes has been causatively linked to human diseases including cancer. Altered patterns of gene expression in normal and cancer cells are the result of inappropriate expression of transcription factors and chromatin modifying proteins. Chromatin immunoprecipitation assay is a well-established tool for investigating the interactions between regulatory proteins and DNA at distinct stages of gene activation. ChIP coupled with DNA microarrays, known as ChIP on chip, or sequencing of DNA associated with the factors (ChIP-Seq) allow us to determine the entire spectrum of in vivo DNA binding sites for a given protein. This has been of immense value because ChIP on chip assays and ChIP-Seq experiments can provide a snapshot of the transcriptional regulatory mechanisms on a genome-wide scale. This chapter outlines the general strategies used to carry out ChIP-chip assays to study the differential recruitment of regulatory molecules based on the studies conducted in our lab as well as other published protocols; these can be easily modified to a ChIP-Seq analysis.
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Affiliation(s)
- Smitha Pillai
- Department of Tumor Biology, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL, 33612, USA
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Lobel L, Sigal N, Borovok I, Belitsky BR, Sonenshein AL, Herskovits AA. The metabolic regulator CodY links Listeria monocytogenes metabolism to virulence by directly activating the virulence regulatory gene prfA. Mol Microbiol 2014; 95:624-44. [PMID: 25430920 DOI: 10.1111/mmi.12890] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2014] [Indexed: 11/30/2022]
Abstract
Metabolic adaptations are critical to the ability of bacterial pathogens to grow within host cells and are normally preceded by sensing of host-specific metabolic signals, which in turn can influence the pathogen's virulence state. Previously, we reported that the intracellular bacterial pathogen Listeria monocytogenes responds to low availability of branched-chain amino acids (BCAAs) within mammalian cells by up-regulating both BCAA biosynthesis and virulence genes. The induction of virulence genes required the BCAA-responsive transcription regulator, CodY, but the molecular mechanism governing this mode of regulation was unclear. In this report, we demonstrate that CodY directly binds the coding sequence of the L. monocytogenes master virulence activator gene, prfA, 15 nt downstream of its start codon, and that this binding results in up-regulation of prfA transcription specifically under low concentrations of BCAA. Mutating this site abolished CodY binding and reduced prfA transcription in macrophages, and attenuated bacterial virulence in mice. Notably, the mutated binding site did not alter prfA transcription or PrfA activity under other conditions that are known to activate PrfA, such as during growth in the presence of glucose-1-phosphate. This study highlights the tight crosstalk between L. monocytogenes metabolism and virulence, while revealing novel features of CodY-mediated regulation.
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Affiliation(s)
- Lior Lobel
- The Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
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Thomas P, Durek P, Solt I, Klinger B, Witzel F, Schulthess P, Mayer Y, Tikk D, Blüthgen N, Leser U. Computer-assisted curation of a human regulatory core network from the biological literature. Bioinformatics 2014; 31:1258-66. [DOI: 10.1093/bioinformatics/btu795] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 11/26/2014] [Indexed: 12/20/2022] Open
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Messerschmidt SJ, Kemter FS, Schindler D, Waldminghaus T. Synthetic secondary chromosomes in Escherichia coli based on the replication origin of chromosome II in Vibrio cholerae. Biotechnol J 2014; 10:302-14. [PMID: 25359671 DOI: 10.1002/biot.201400031] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 10/02/2014] [Accepted: 10/30/2014] [Indexed: 01/25/2023]
Abstract
Recent developments in DNA-assembly methods make the synthesis of synthetic chromosomes a reachable goal. However, the redesign of primary chromosomes bears high risks and still requires enormous resources. An alternative approach is the addition of synthetic chromosomes to the cell. The natural secondary chromosome of Vibrio cholerae could potentially serve as template for a synthetic secondary chromosome in Escherichia coli. To test this assumption we constructed a replicon named synVicII based on the replication module of V. cholerae chromosome II (oriII). A new assay for the assessment of replicon stability was developed based on flow-cytometric analysis of unstable GFP variants. Application of this assay to cells carrying synVicII revealed an improved stability compared to a secondary replicon based on E. coli oriC. Cell cycle analysis and determination of cellular copy numbers of synVicII indicate that replication timing of the synthetic replicon in E. coli is comparable to the natural chromosome II (ChrII) in V. cholerae. The presented synthetic biology work provides the basis to use secondary chromosomes in E. coli to answer basic research questions as well as for several biotechnological applications.
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Affiliation(s)
- Sonja J Messerschmidt
- LOEWE Center for Synthetic Microbiology, SYNMIKRO, Philipps-Universität Marburg, Germany
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Expanding the regulatory network governed by the extracytoplasmic function sigma factor σH in Corynebacterium glutamicum. J Bacteriol 2014; 197:483-96. [PMID: 25404703 DOI: 10.1128/jb.02248-14] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The extracytoplasmic function sigma factor σ(H) is responsible for the heat and oxidative stress response in Corynebacterium glutamicum. Due to the hierarchical nature of the regulatory network, previous transcriptome analyses have not been able to discriminate between direct and indirect targets of σ(H). Here, we determined the direct genome-wide targets of σ(H) using chromatin immunoprecipitation with microarray technology (ChIP-chip) for analysis of a deletion mutant of rshA, encoding an anti-σ factor of σ(H). Seventy-five σ(H)-dependent promoters, including 39 new ones, were identified. σ(H)-dependent, heat-inducible transcripts for several of the new targets, including ilvD encoding a labile Fe-S cluster enzyme, dihydroxy-acid dehydratase, were detected, and their 5' ends were mapped to the σ(H)-dependent promoters identified. Interestingly, functional internal σ(H)-dependent promoters were found in operon-like gene clusters involved in the pentose phosphate pathway, riboflavin biosynthesis, and Zn uptake. Accordingly, deletion of rshA resulted in hyperproduction of riboflavin and affected expression of Zn-responsive genes, possibly through intracellular Zn overload, indicating new physiological roles of σ(H). Furthermore, sigA encoding the primary σ factor was identified as a new target of σ(H). Reporter assays demonstrated that the σ(H)-dependent promoter upstream of sigA was highly heat inducible but much weaker than the known σ(A)-dependent one. Our ChIP-chip analysis also detected the σ(H)-dependent promoters upstream of rshA within the sigH-rshA operon and of sigB encoding a group 2 σ factor, supporting the previous findings of their σ(H)-dependent expression. Taken together, these results reveal an additional layer of the sigma factor regulatory network in C. glutamicum.
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Genome-wide analysis of the role of global transcriptional regulator GntR1 in Corynebacterium glutamicum. J Bacteriol 2014; 196:3249-58. [PMID: 24982307 DOI: 10.1128/jb.01860-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The transcriptional regulator GntR1 downregulates the genes for gluconate catabolism and pentose phosphate pathway in Corynebacterium glutamicum. Gluconate lowers the DNA binding affinity of GntR1, which is probably the mechanism of gluconate-dependent induction of these genes. In addition, GntR1 positively regulates ptsG, a gene encoding a major glucose transporter, and pck, a gene encoding phosphoenolpyruvate carboxykinase. Here, we searched for the new target of GntR1 on a genome-wide scale by chromatin immunoprecipitation in conjunction with microarray (ChIP-chip) analysis. This analysis identified 56 in vivo GntR1 binding sites, of which 7 sites were previously reported. The newly identified GntR1 sites include the upstream regions of carbon metabolism genes such as pyk, maeB, gapB, and icd, encoding pyruvate kinase, malic enzyme, glyceraldehyde 3-phosphate dehydrogenase B, and isocitrate dehydrogenase, respectively. Binding of GntR1 to the promoter region of these genes was confirmed by electrophoretic mobility shift assay. The activity of the icd, gapB, and maeB promoters was reduced by the mutation at the GntR1 binding site, in contrast to the pyk promoter activity, which was increased, indicating that GntR1 is a transcriptional activator of icd, gapB, and maeB and is a repressor of pyk. Thus, it is likely that GntR1 stimulates glucose uptake by inducing the phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS) gene while repressing pyk to increase PEP availability in the absence of gluconate. Repression of zwf and gnd may reduce the NADPH supply, which may be compensated by the induction of maeB and icd. Upregulation of icd, gapB, and maeB and downregulation of pyk by GntR1 probably support gluconeogenesis.
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Göpel Y, Görke B. Lies and deception in bacterial gene regulation: the roles of nucleic acid decoys. Mol Microbiol 2014; 92:641-7. [PMID: 24707963 DOI: 10.1111/mmi.12604] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/03/2014] [Indexed: 12/24/2022]
Abstract
Bacteria use intricately interconnected mechanisms acting at the transcriptional and post-transcriptional level to adjust gene expression to their needs. An intriguing example found in the chitosugar utilization systems of Escherichia coli and Salmonella is uncovered in a study by Plumbridge and colleagues. Three transcription factors (TFs), a small regulatory RNA (sRNA) and a sRNA trap cooperate to set thresholds and dynamics in regulation of chitosugar utilization. Specifically, under inducing conditions a decoy site on the polycistronic chitobiose (chbBCARFG) mRNA sequesters sRNA ChiX, which represses synthesis of the separately encoded chitoporin ChiP. Base-pairing of ChiX with its decoy has no role for the chb genes themselves when the mRNA is in excess. In the absence of substrate, however, this base-pairing tightly represses chbC encoding a subunit of the chitosugar transporter. Thus, one and the same sRNA/mRNA interaction serves different regulatory functions under different environmental conditions. The employment of RNA decoys to control the activities of post-transcriptional regulators themselves is an increasingly recognized mechanism in gene regulation. Another observation in the current study highlights the possibility that decoy sites might even exist on the DNA controlling the availability of TFs for their target promoters.
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Affiliation(s)
- Yvonne Göpel
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, Center of Molecular Biology, University of Vienna, 1030, Vienna, Austria
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Abstract
Bacterial adaptation to given environmental conditions is largely achieved by complex gene regulatory processes. To address the question how and to what extend single transcriptional regulators modulate gene expression, chromatin immunoprecipitation (ChIP) coupled to DNA microarrays (ChIP-chip) or to next-generation sequencing (ChIP-seq) is one of the preferred methods. Both ChIP-chip and ChIP-seq can generate genome-wide maps of protein-DNA interactions and thus identify primary regulons of transcription factors. In combination with transcriptome analyses, the obtained data can be used to compile complex regulatory networks which in terms will advance our understanding of bacterial adaptation processes to specific environmental conditions.
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Affiliation(s)
- Sebastian Schulz
- Twincore, Centre of Experimental and Clinical Infection Research, Feodor-Lynen-Str. 7, 30625, Hannover, Germany
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Flåtten I, Skarstad K. The Fis protein has a stimulating role in initiation of replication in Escherichia coli in vivo. PLoS One 2013; 8:e83562. [PMID: 24358293 PMCID: PMC3865182 DOI: 10.1371/journal.pone.0083562] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 11/13/2013] [Indexed: 12/31/2022] Open
Abstract
The Fis protein is a nucleoid associated protein that has previously been reported to act negatively in initiation of replication in Escherichia coli. In this work we have examined the influence of this protein on the initiation of replication under different growth conditions using flow cytometry. The Fis protein was found to be increasingly important with increasing growth rate. During multi-fork replication severe under-initiation occurred in cells lacking the Fis protein; the cells initiated at an elevated mass, had fewer origins per cell and the origins were not initiated in synchrony. These results suggest a positive role for the Fis protein in the initiation of replication.
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Affiliation(s)
- Ingvild Flåtten
- Department of Cell Biology, Institute for Cancer Research, The Norwegian Radiumhospital, Oslo University Hospital, Oslo, Norway
| | - Kirsten Skarstad
- Department of Cell Biology, Institute for Cancer Research, The Norwegian Radiumhospital, Oslo University Hospital, Oslo, Norway
- * E-mail:
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Mahdavi J, Royer PJ, Sjölinder HS, Azimi S, Self T, Stoof J, Wheldon LM, Brännström K, Wilson R, Moreton J, Moir JWB, Sihlbom C, Borén T, Jonsson AB, Soultanas P, Ala'Aldeen DAA. Pro-inflammatory cytokines can act as intracellular modulators of commensal bacterial virulence. Open Biol 2013; 3:130048. [PMID: 24107297 PMCID: PMC3814720 DOI: 10.1098/rsob.130048] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Interactions between commensal pathogens and hosts are critical for disease development but the underlying mechanisms for switching between the commensal and virulent states are unknown. We show that the human pathogen Neisseria meningitidis, the leading cause of pyogenic meningitis, can modulate gene expression via uptake of host pro-inflammatory cytokines leading to increased virulence. This uptake is mediated by type IV pili (Tfp) and reliant on the PilT ATPase activity. Two Tfp subunits, PilE and PilQ, are identified as the ligands for TNF-α and IL-8 in a glycan-dependent manner, and their deletion results in decreased virulence and increased survival in a mouse model. We propose a novel mechanism by which pathogens use the twitching motility mode of the Tfp machinery for sensing and importing host elicitors, aligning with the inflamed environment and switching to the virulent state.
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Affiliation(s)
- Jafar Mahdavi
- School of Life Sciences, Molecular Bacteriology and Immunology Group, University of Nottingham, Nottingham NG7 2RD, UK
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Schindler D, Waldminghaus T. "Non-canonical protein-DNA interactions identified by ChIP are not artifacts": response. BMC Genomics 2013; 14:638. [PMID: 24053571 PMCID: PMC3870955 DOI: 10.1186/1471-2164-14-638] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 09/18/2013] [Indexed: 11/10/2022] Open
Abstract
Background Studies of protein association with DNA on a genome wide scale are possible through methods like ChIP-Chip or ChIP-Seq. Massive problems with false positive signals in our own experiments motivated us to revise the standard ChIP-Chip protocol. Analysis of chromosome wide binding of the alternative sigma factor σ32 in Escherichia coli with this new protocol resulted in detection of only a subset of binding sites found in a previous study by Wade and colleagues. We suggested that the remainder of binding sites detected in the previous study are likely to be false positives. In a recent article the Wade group claimed that our conclusion is wrong and that the disputed sites are genuine σ32 binding sites. They further claimed that the non-detection of these sites in our study was due to low data quality. Results/discussion We respond to the criticism of Wade and colleagues and discuss some general questions of ChIP-based studies. We outline why the quality of our data is sufficient to derive meaningful results. Specific points are: (i) the modifications we introduced into the standard ChIP-Chip protocol do not necessarily result in a low dynamic range, (ii) correlation between ChIP-Chip replicates should not be calculated based on the whole data set as done in transcript analysis, (iii) control experiments are essential for identifying false positives. Suggestions are made how ChIP-based methods could be further optimized and which alternative approaches can be used to strengthen conclusions. Conclusion We appreciate the ongoing discussion about the ChIP-Chip method and hope that it helps other scientist to analyze and interpret their results. The modifications we introduced into the ChIP-Chip protocol are a first step towards reducing false positive signals but there is certainly potential for further optimization. The discussion about the σ32 binding sites in question highlights the need for alternative approaches and further investigation of appropriate methods for verification.
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Affiliation(s)
- Daniel Schindler
- LOEWE-Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Hans-Meerwein-Str, 6, D-35043, Marburg, Germany.
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Regulation of sister chromosome cohesion by the replication fork tracking protein SeqA. PLoS Genet 2013; 9:e1003673. [PMID: 23990792 PMCID: PMC3749930 DOI: 10.1371/journal.pgen.1003673] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 06/12/2013] [Indexed: 01/12/2023] Open
Abstract
Analogously to chromosome cohesion in eukaryotes, newly replicated DNA in E. coli is held together by inter-sister linkages before partitioning into daughter nucleoids. In both cases, initial joining is apparently mediated by DNA catenation, in which replication-induced positive supercoils diffuse behind the fork, causing newly replicated duplexes to twist around each other. Type-II topoisomerase-catalyzed sister separation is delayed by the well-characterized cohesin complex in eukaryotes, but cohesion control in E. coli is not currently understood. We report that the abundant fork tracking protein SeqA is a strong positive regulator of cohesion, and is responsible for markedly prolonged cohesion observed at “snap” loci. Epistasis analysis suggests that SeqA stabilizes cohesion by antagonizing Topo IV-mediated sister resolution, and possibly also by a direct bridging mechanism. We show that variable cohesion observed along the E. coli chromosome is caused by differential SeqA binding, with oriC and snap loci binding disproportionally more SeqA. We propose that SeqA binding results in loose inter-duplex junctions that are resistant to Topo IV cleavage. Lastly, reducing cohesion by genetic manipulation of Topo IV or SeqA resulted in dramatically slowed sister locus separation and poor nucleoid partitioning, indicating that cohesion has a prominent role in chromosome segregation. Sister chromosome cohesion in eukaryotes maintains genome stability by mediating chromosome segregation and homologous recombination-dependent DNA repair. Here we have investigated the mechanism of cohesion regulation in E. coli by measuring cohesion timing in a broad set of candidate mutant strains. Using a sensitive DNA replication and segregation assay, we show that cohesion is controlled by the conserved DNA decatenation enzyme Topo IV and the abundant DNA binding protein SeqA. Results suggest that cohesion occurs in E. coli by twisting of replicated duplexes around each other behind the replication fork, and immediate resolution of cohered regions is blocked by SeqA. SeqA binds to a sliding 300–400 kb window of hemimethylated DNA behind the fork, and regions binding more SeqA experience longer cohesion periods. An analogous decatenation inhibition function is carried out by the cohesin complex in eukaryotes, indicating that cells mediate pairing and separation of replicated DNA by a conserved mechanism. In both cases, mismanaged cohesion results in failed or inefficient chromosome segregation.
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Yang J, Mitra A, Dojer N, Fu S, Rowicka M, Brasier AR. A probabilistic approach to learn chromatin architecture and accurate inference of the NF-κB/RelA regulatory network using ChIP-Seq. Nucleic Acids Res 2013; 41:7240-59. [PMID: 23771139 PMCID: PMC3753626 DOI: 10.1093/nar/gkt493] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Using nuclear factor-κB (NF-κB) ChIP-Seq data, we present a framework for iterative learning of regulatory networks. For every possible transcription factor-binding site (TFBS)-putatively regulated gene pair, the relative distance and orientation are calculated to learn which TFBSs are most likely to regulate a given gene. Weighted TFBS contributions to putative gene regulation are integrated to derive an NF-κB gene network. A de novo motif enrichment analysis uncovers secondary TFBSs (AP1, SP1) at characteristic distances from NF-κB/RelA TFBSs. Comparison with experimental ENCODE ChIP-Seq data indicates that experimental TFBSs highly correlate with predicted sites. We observe that RelA-SP1-enriched promoters have distinct expression profiles from that of RelA-AP1 and are enriched in introns, CpG islands and DNase accessible sites. Sixteen novel NF-κB/RelA-regulated genes and TFBSs were experimentally validated, including TANK, a negative feedback gene whose expression is NF-κB/RelA dependent and requires a functional interaction with the AP1 TFBSs. Our probabilistic method yields more accurate NF-κB/RelA-regulated networks than a traditional, distance-based approach, confirmed by both analysis of gene expression and increased informativity of Genome Ontology annotations. Our analysis provides new insights into how co-occurring TFBSs and local chromatin context orchestrate activation of NF-κB/RelA sub-pathways differing in biological function and temporal expression patterns.
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Affiliation(s)
- Jun Yang
- Department of Internal Medicine, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1060, USA, Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1060, USA, Institute for Translational Sciences, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1060, USA, Institute of Informatics, University of Warsaw, Banacha 2, 02-097, Warsaw, Poland and Sealy Center for Molecular Medicine, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1060, USA
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Bonocora RP, Fitzgerald DM, Stringer AM, Wade JT. Non-canonical protein-DNA interactions identified by ChIP are not artifacts. BMC Genomics 2013; 14:254. [PMID: 23586855 PMCID: PMC3738151 DOI: 10.1186/1471-2164-14-254] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 04/01/2013] [Indexed: 02/01/2023] Open
Abstract
Background ChIP-chip and ChIP-seq are widely used methods to map protein-DNA interactions on a genomic scale in vivo. Waldminghaus and Skarstad recently reported, in this journal, a modified method for ChIP-chip. Based on a comparison of our previously-published ChIP-chip data for Escherichia coli σ32 with their own data, Waldminghaus and Skarstad concluded that many of the σ32 targets identified in our earlier work are false positives. In particular, we identified many non-canonical σ32 targets that are located inside genes or are associated with genes that show no detectable regulation by σ32. Waldminghaus and Skarstad propose that such non-canonical sites are artifacts, identified due to flaws in the standard ChIP methodology. Waldminghaus and Skarstad suggest specific changes to the standard ChIP procedure that reportedly eliminate the claimed artifacts. Results We reanalyzed our published ChIP-chip datasets for σ32 and the datasets generated by Waldminghaus and Skarstad to assess data quality and reproducibility. We also performed targeted ChIP/qPCR for σ32 and an unrelated transcription factor, AraC, using the standard ChIP method and the modified ChIP method proposed by Waldminghaus and Skarstad. Furthermore, we determined the association of core RNA polymerase with disputed σ32 promoters, with and without overexpression of σ32. We show that (i) our published σ32 ChIP-chip datasets have a consistently higher dynamic range than those of Waldminghaus and Skarstad, (ii) our published σ32 ChIP-chip datasets are highly reproducible, whereas those of Waldminghaus and Skarstad are not, (iii) non-canonical σ32 target regions are enriched in a σ32 ChIP in a heat shock-dependent manner, regardless of the ChIP method used, (iv) association of core RNA polymerase with some disputed σ32 target genes is induced by overexpression of σ32, (v) σ32 targets disputed by Waldminghaus and Skarstad are predominantly those that are most weakly bound, and (vi) the modifications to the ChIP method proposed by Waldminghaus and Skarstad reduce enrichment of all protein-bound genomic regions. Conclusions The modifications to the ChIP-chip method suggested by Waldminghaus and Skarstad reduce rather than increase the quality of ChIP data. Hence, the non-canonical σ32 targets identified in our previous study are likely to be genuine. We propose that the failure of Waldminghaus and Skarstad to identify many of these σ32 targets is due predominantly to the lower data quality in their study. We conclude that surprising ChIP-chip results are not artifacts to be ignored, but rather indications that our understanding of DNA-binding proteins is incomplete.
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Weiss V, Medina-Rivera A, Huerta AM, Santos-Zavaleta A, Salgado H, Morett E, Collado-Vides J. Evidence classification of high-throughput protocols and confidence integration in RegulonDB. DATABASE-THE JOURNAL OF BIOLOGICAL DATABASES AND CURATION 2013; 2013:bas059. [PMID: 23327937 PMCID: PMC3548332 DOI: 10.1093/database/bas059] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
RegulonDB provides curated information on the transcriptional regulatory network of Escherichia coli and contains both experimental data and computationally predicted objects. To account for the heterogeneity of these data, we introduced in version 6.0, a two-tier rating system for the strength of evidence, classifying evidence as either ‘weak’ or ‘strong’ (Gama-Castro,S., Jimenez-Jacinto,V., Peralta-Gil,M. et al. RegulonDB (Version 6.0): gene regulation model of Escherichia Coli K-12 beyond transcription, active (experimental) annotated promoters and textpresso navigation. Nucleic Acids Res., 2008;36:D120–D124.). We now add to our classification scheme the classification of high-throughput evidence, including chromatin immunoprecipitation (ChIP) and RNA-seq technologies. To integrate these data into RegulonDB, we present two strategies for the evaluation of confidence, statistical validation and independent cross-validation. Statistical validation involves verification of ChIP data for transcription factor-binding sites, using tools for motif discovery and quality assessment of the discovered matrices. Independent cross-validation combines independent evidence with the intention to mutually exclude false positives. Both statistical validation and cross-validation allow to upgrade subsets of data that are supported by weak evidence to a higher confidence level. Likewise, cross-validation of strong confidence data extends our two-tier rating system to a three-tier system by introducing a third confidence score ‘confirmed’. Database URL:http://regulondb.ccg.unam.mx/
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Affiliation(s)
- Verena Weiss
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, AP 565-A, Cuernavaca, Morelos 62100, Mexico.
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Abstract
Transcriptional and posttranscriptional regulators play a critical role in allowing a bacterium to adapt to the diverse environments and conditions it encounters. In order to characterize the role of these regulators the identification of their specific interaction partners is of utmost importance. Co-immunoprecipitation (IP) is based on antigen/antibody complex formation to purify a protein of interest from the rest of the samples together with its interaction partner. This method allows us to study direct interaction of a regulator with its specific binding partners like protein-RNA, protein-DNA, or protein-protein interactions. IP typically requires careful optimization and troubleshooting depending on the varying physicochemical characteristics of the protein of interest. In this chapter we present a starting point and the basic guidelines to obtain the best possible results from an IP experiment with subsequent use of new-generation sequencing techniques to detect mRNA or ncRNA targets (RIPseq) and protein-DNA interactions (ChIPseq).
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Affiliation(s)
- Tobias Sahr
- Biologie des Bactéries Intracellulaires, Institut Pasteur, Paris, France
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Dillon SC, Espinosa E, Hokamp K, Ussery DW, Casadesús J, Dorman CJ. LeuO is a global regulator of gene expression inSalmonella entericaserovar Typhimurium. Mol Microbiol 2012; 85:1072-89. [DOI: 10.1111/j.1365-2958.2012.08162.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Dual RpoH sigma factors and transcriptional plasticity in a symbiotic bacterium. J Bacteriol 2012; 194:4983-94. [PMID: 22773790 DOI: 10.1128/jb.00449-12] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Sinorhizobium meliloti can live as a soil saprophyte and can engage in a nitrogen-fixing symbiosis with plant roots. To succeed in such diverse environments, the bacteria must continually adjust gene expression. Transcriptional plasticity in eubacteria is often mediated by alternative sigma (σ) factors interacting with core RNA polymerase. The S. meliloti genome encodes 14 of these alternative σ factors, including two putative RpoH ("heat shock") σ factors. We used custom Affymetrix symbiosis chips to characterize the global transcriptional response of S. meliloti rpoH1, rpoH2, and rpoH1 rpoH2 mutants during heat shock and stationary-phase growth. Under these conditions, expression of over 300 genes is dependent on rpoH1 and rpoH2. We mapped transcript start sites of 69 rpoH-dependent genes using 5' RACE (5' rapid amplification of cDNA ends), which allowed us to determine putative RpoH1-dependent, RpoH2-dependent, and dual-promoter (RpoH1- and RpoH2-dependent) consensus sequences that were each used to search the genome for other potential direct targets of RpoH. The inferred S. meliloti RpoH promoter consensus sequences share features of Escherichia coli RpoH promoters but lack extended -10 motifs.
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Abstract
INTRODUCTION The interpretation of high-throughput profiling data depends on the pathway analysis database. Currently, pathway analysis often has to rely on a set of interactions and pathways measured in every possible human tissue, due to insufficient knowledge about interactions and pathways in the context of the profiling experiment. However, a recent global scale analysis of human tissue proteomes and interactomes reveals significant differences among tissues, suggesting that interaction and pathway data that are used out of biological context are the major source of inaccuracies and noise in the analysis of profiling data. AREAS COVERED In this review, the major classes of biological context used for experimental detection of molecular interactions and pathways in molecular biology are described. Furthermore, the author reviews methods for predicting biological interactions in order to evaluate the applicability of various contextual interaction data in pathway analysis. Using the results from recent publications that study large-scale tissue composition, the article provides an estimation of the gain in pathway analysis accuracy if only the interactions predicted for the context of a molecular profiling experiment are used, relative to the analysis performed with a context-independent knowledge base. EXPERT OPINION It is of the author's opinion that the major source of inaccuracy in pathway analysis is the lack of knowledge about tissue-specific transcriptional regulation. It is therefore suggested that the accuracy of the analysis can be substantially improved if only context-specific interactions and pathways are used for interpretation.
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Affiliation(s)
- Anton Yuryev
- Elsevier, Ariadne Genomics, Inc., Rockville, MD 20878, USA.
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Waldminghaus T, Weigel C, Skarstad K. Replication fork movement and methylation govern SeqA binding to the Escherichia coli chromosome. Nucleic Acids Res 2012; 40:5465-76. [PMID: 22373925 PMCID: PMC3384311 DOI: 10.1093/nar/gks187] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In Escherichia coli, the SeqA protein binds specifically to GATC sequences which are methylated on the A of the old strand but not on the new strand. Such hemimethylated DNA is produced by progression of the replication forks and lasts until Dam methyltransferase methylates the new strand. It is therefore believed that a region of hemimethylated DNA covered by SeqA follows the replication fork. We show that this is, indeed, the case by using global ChIP on Chip analysis of SeqA in cells synchronized regarding DNA replication. To assess hemimethylation, we developed the first genome-wide method for methylation analysis in bacteria. Since loss of the SeqA protein affects growth rate only during rapid growth when cells contain multiple replication forks, a comparison of rapid and slow growth was performed. In cells with six replication forks per chromosome, the two old forks were found to bind surprisingly little SeqA protein. Cell cycle analysis showed that loss of SeqA from the old forks did not occur at initiation of the new forks, but instead occurs at a time point coinciding with the end of SeqA-dependent origin sequestration. The finding suggests simultaneous origin de-sequestration and loss of SeqA from old replication forks.
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Affiliation(s)
- Torsten Waldminghaus
- Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital and University of Oslo, 0310 Oslo, Norway
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Tian B, Yang J, Brasier AR. Two-step cross-linking for analysis of protein-chromatin interactions. Methods Mol Biol 2012; 809:105-20. [PMID: 22113271 DOI: 10.1007/978-1-61779-376-9_7] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Eukaryotic gene regulation is controlled, in part, by inducible transcription factor-binding regulatory sequences in a tissue-specific and hormone-responsive manner. The development of methods for the analysis of transcription factor interaction within native chromatin has been a significant advance for the systematic analyses of the timing of gene regulation and studies on the effects of chromatin modifying enzymes on promoter accessibility. Chromatin immunoprecipitation (ChIP) is a specific method involving formaldehyde mediated protein-chromatin fixation to preserve the interaction for subsequent target identification. However, the conventional single-step cross-linking technique does not preserve all protein-DNA interactions, especially for transcription factors in hyper-dynamic equilibrium with chromatin or for coactivator interactions. Here, we describe a versatile, efficient "two-step" XChIP method that involves sequential protein-protein fixation followed by protein-DNA fixation. This method has been used successfully for analysis of chromatin binding for transcription factors (NF-κB, STAT3), polymerases (RNA Pol II), coactivators (CBP/p300, CDK9), and chromatin structural proteins (modified histones). Modifications of DNA extraction and sonication suitable for downstream target identification by quantitative genomic PCR and next generation sequencing are described.
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Affiliation(s)
- Bing Tian
- Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX, USA
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