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Yan Y, Xu W, Kumar S, Zhang A, Leng F, Dunlap D, Finzi L. Negative DNA supercoiling makes protein-mediated looping deterministic and ergodic within the bacterial doubling time. Nucleic Acids Res 2021; 49:11550-11559. [PMID: 34723343 PMCID: PMC8599721 DOI: 10.1093/nar/gkab946] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 09/28/2021] [Accepted: 10/04/2021] [Indexed: 11/14/2022] Open
Abstract
Protein-mediated DNA looping is fundamental to gene regulation and such loops occur stochastically in purified systems. Additional proteins increase the probability of looping, but these probabilities maintain a broad distribution. For example, the probability of lac repressor-mediated looping in individual molecules ranged 0–100%, and individual molecules exhibited representative behavior only in observations lasting an hour or more. Titrating with HU protein progressively compacted the DNA without narrowing the 0–100% distribution. Increased negative supercoiling produced an ensemble of molecules in which all individual molecules more closely resembled the average. Furthermore, in only 12 min of observation, well within the doubling time of the bacterium, most molecules exhibited the looping probability of the ensemble. DNA supercoiling, an inherent feature of all genomes, appears to impose time-constrained, emergent behavior on otherwise random molecular activity.
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Affiliation(s)
- Yan Yan
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Wenxuan Xu
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Sandip Kumar
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Alexander Zhang
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Fenfei Leng
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - David Dunlap
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Laura Finzi
- Physics Department, Emory University, Atlanta, GA 30322, USA
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Oliveira Paiva AM, Friggen AH, Qin L, Douwes R, Dame RT, Smits WK. The Bacterial Chromatin Protein HupA Can Remodel DNA and Associates with the Nucleoid in Clostridium difficile. J Mol Biol 2019; 431:653-672. [PMID: 30633871 DOI: 10.1016/j.jmb.2019.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 12/19/2018] [Accepted: 01/02/2019] [Indexed: 12/15/2022]
Abstract
The maintenance and organization of the chromosome plays an important role in the development and survival of bacteria. Bacterial chromatin proteins are architectural proteins that bind DNA and modulate its conformation, and by doing so affect a variety of cellular processes. No bacterial chromatin proteins of Clostridium difficile have been characterized to date. Here, we investigate aspects of the C. difficile HupA protein, a homologue of the histone-like HU proteins of Escherichia coli. HupA is a 10-kDa protein that is present as a homodimer in vitro and self-interacts in vivo. HupA co-localizes with the nucleoid of C. difficile. It binds to the DNA without a preference for the DNA G + C content. Upon DNA binding, HupA induces a conformational change in the substrate DNA in vitro and leads to compaction of the chromosome in vivo. The present study is the first to characterize a bacterial chromatin protein in C. difficile and opens the way to study the role of chromosomal organization in DNA metabolism and on other cellular processes in this organism.
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Affiliation(s)
- Ana M Oliveira Paiva
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, the Netherlands; Center for Microbial Cell Biology, Leiden, the Netherlands
| | - Annemieke H Friggen
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, the Netherlands; Center for Microbial Cell Biology, Leiden, the Netherlands
| | - Liang Qin
- Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, the Netherlands; Center for Microbial Cell Biology, Leiden, the Netherlands
| | - Roxanne Douwes
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, the Netherlands
| | - Remus T Dame
- Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, the Netherlands; Center for Microbial Cell Biology, Leiden, the Netherlands
| | - Wiep Klaas Smits
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, the Netherlands; Center for Microbial Cell Biology, Leiden, the Netherlands.
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Cyclo-(l-Phe-l-Pro), a Quorum-Sensing Signal of Vibrio vulnificus, Induces Expression of Hydroperoxidase through a ToxR-LeuO-HU-RpoS Signaling Pathway To Confer Resistance against Oxidative Stress. Infect Immun 2018; 86:IAI.00932-17. [PMID: 29914931 PMCID: PMC6105893 DOI: 10.1128/iai.00932-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 06/06/2018] [Indexed: 12/17/2022] Open
Abstract
Vibrio vulnificus, an opportunistic human pathogen, produces cyclo-(l-Phe-l-Pro) (cFP), which serves as a signaling molecule controlling the ToxR-dependent expression of innate bacterial genes, and also as a virulence factor eliciting pathogenic effects on human cells by enhancing intracellular reactive oxygen species levels. We found that cFP facilitated the protection of V. vulnificus against hydrogen peroxide. At a concentration of 1 mM, cFP enhanced the level of the transcriptional regulator RpoS, which in turn induced expression of katG, encoding hydroperoxidase I, an enzyme that detoxifies H2O2 to overcome oxidative stress. We found that cFP upregulated the transcription of the histone-like proteins vHUα and vHUβ through the cFP-dependent regulator LeuO. LeuO binds directly to upstream regions of vhuA and vhuB to enhance transcription. vHUα and vHUβ then enhance the level of RpoS posttranscriptionally by stabilizing the mRNA. This cFP-mediated ToxR-LeuO-vHUαβ-RpoS pathway also upregulates genes known to be members of the RpoS regulon, suggesting that cFP acts as a cue for the signaling pathway responsible for both the RpoS and the LeuO regulons. Taken together, this study shows that cFP plays an important role as a virulence factor, as well as a signal for the protection of the cognate pathogen.
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Álvarez A, Toledo H. The histone-like protein HU has a role in gene expression during the acid adaptation response in Helicobacter pylori. Helicobacter 2017; 22. [PMID: 28244177 DOI: 10.1111/hel.12381] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
BACKGROUND Gastritis, ulcers, and gastric malignancy have been linked to human gastric epithelial colonization by Helicobacter pylori. Characterization of the mechanisms by which H. pylori adapts to the human stomach environment is of crucial importance to understand H. pylori pathogenesis. MATERIAL AND METHODS In an effort to extend our knowledge of these mechanisms, we used proteomic analysis and qRT-PCR to characterize the role of the histone-like protein HU in the response of H. pylori to low pH. RESULTS Proteomic analysis revealed that genes involved in chemotaxis, oxidative stress, or metabolism are under control of the HU protein. Also, expression of the virulence factors Ggt and NapA is affected by the null mutation of hup gene both at neutral and acid pH, as evidenced by qRT-PCR analysis. CONCLUSIONS Those results showed that H. pylori gene expression is altered by shift to low pH, thus confirming that acid exposure leads to profound changes in genomic expression, and suggest that the HU protein is a regulator that may help the bacterium adapt to the acid stress. In accordance with previous reports, we found that the HU protein participates in gene expression regulation when the microorganism is exposed to acid stress. Such transcriptional regulation underlies protein accumulation in the H. pylori cell.
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Affiliation(s)
- Alhejandra Álvarez
- Laboratory of Molecular Microbiology, Department of Molecular and Cellular Biology, Faculty of Medicine, ICBM, University of Chile, Santiago, Chile
| | - Héctor Toledo
- Laboratory of Molecular Microbiology, Department of Molecular and Cellular Biology, Faculty of Medicine, ICBM, University of Chile, Santiago, Chile
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Genes on a Wire: The Nucleoid-Associated Protein HU Insulates Transcription Units in Escherichia coli. Sci Rep 2016; 6:31512. [PMID: 27545593 PMCID: PMC4992867 DOI: 10.1038/srep31512] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 07/21/2016] [Indexed: 01/06/2023] Open
Abstract
The extent to which chromosomal gene position in prokaryotes affects local gene expression remains an open question. Several studies have shown that chromosomal re-positioning of bacterial transcription units does not alter their expression pattern, except for a general decrease in gene expression levels from chromosomal origin to terminus proximal positions, which is believed to result from gene dosage effects. Surprisingly, the question as to whether this chromosomal context independence is a cis encoded property of a bacterial transcription unit, or if position independence is a property conferred by factors acting in trans, has not been addressed so far. For this purpose, we established a genetic test system assessing the chromosomal positioning effects by means of identical promoter-fluorescent reporter gene fusions inserted equidistantly from OriC into both chromosomal replichores of Escherichia coli K-12. Our investigations of the reporter activities in mutant cells lacking the conserved nucleoid associated protein HU uncovered various drastic chromosomal positional effects on gene transcription. In addition we present evidence that these positional effects are caused by transcriptional activity nearby the insertion site of our reporter modules. We therefore suggest that the nucleoid-associated protein HU is functionally insulating transcription units, most likely by constraining transcription induced DNA supercoiling.
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Kim DH, Im H, Jee JG, Jang SB, Yoon HJ, Kwon AR, Kang SM, Lee BJ. β-Arm flexibility of HU fromStaphylococcus aureusdictates the DNA-binding and recognition mechanism. ACTA ACUST UNITED AC 2014; 70:3273-89. [DOI: 10.1107/s1399004714023931] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 10/30/2014] [Indexed: 12/11/2022]
Abstract
HU, one of the major nucleoid-associated proteins, interacts with the minor groove of DNA in a nonspecific manner to induce DNA bending or to stabilize bent DNA. In this study, crystal structures are reported for both free HU fromStaphylococcus aureusMu50 (SHU) and SHU bound to 21-mer dsDNA. The structures, in combination with electrophoretic mobility shift assays (EMSAs), isothermal titration calorimetry (ITC) measurements and molecular-dynamics (MD) simulations, elucidate the overall and residue-specific changes in SHU upon recognizing and binding to DNA. Firstly, structural comparison showed the flexible nature of the β-sheets of the DNA-binding domain and that the β-arms bend inwards upon complex formation, whereas the other portions are nearly unaltered. Secondly, it was found that the disruption and formation of salt bridges accompanies DNA binding. Thirdly, residue-specific free-energy analyses using the MM-PBSA method with MD simulation data suggested that the successive basic residues in the β-arms play a central role in recognizing and binding to DNA, which was confirmed by the EMSA and ITC analyses. Moreover, residue Arg55 resides in the hinge region of the flexible β-arms, exhibiting a remarkable role in their flexible nature. Fourthly, EMSAs with various DNAs revealed that SHU prefers deformable DNA. Taken together, these data suggest residue-specific roles in local shape and base readouts, which are primarily mediated by the flexible β-arms consisting of residues 50–80.
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The regulation of HanA during heterocyst development in cyanobacterium Anabaena sp. PCC 7120. World J Microbiol Biotechnol 2014; 30:2673-80. [PMID: 24980942 DOI: 10.1007/s11274-014-1691-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 06/17/2014] [Indexed: 10/25/2022]
Abstract
In response to deprivation of combined nitrogen, the filamentous cyanobacterium Anabaena sp. strain PCC 7120 develops heterocyst, which is specifically involved in the nitrogen fixation. In this study, we focused on the regulation of HanA, a histone-like protein, in heterocyst development. Electrophoretic mobility shift assay results showed that NtcA, a global nitrogen regulator necessary for heterocyst differentiation, could bind to two NtcA-binding motifs in the hanA promoter region. qPCR results also showed that NtcA may regulate the expression of hanA. By using the hanA promoter-controlled gfp as a reporter gene and performing western blot we found that the amount of HanA in mature heterocysts was decreased gradually.
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Priyadarshini R, Cugini C, Arndt A, Chen T, Tjokro NO, Goodman SD, Davey ME. The nucleoid-associated protein HUβ affects global gene expression in Porphyromonas gingivalis. MICROBIOLOGY-SGM 2012; 159:219-229. [PMID: 23175503 DOI: 10.1099/mic.0.061002-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
HU is a non-sequence-specific DNA-binding protein and one of the most abundant nucleoid-associated proteins in the bacterial cell. Like Escherichia coli, the genome of Porphyromonas gingivalis is predicted to encode both the HUα (PG1258) and the HUβ (PG0121) subunit. We have previously reported that PG0121 encodes a non-specific DNA-binding protein and that PG0121 is co-transcribed with the K-antigen capsule synthesis operon. We also reported that deletion of PG0121 resulted in downregulation of capsule operon expression and produced a P. gingivalis strain that is phenotypically deficient in surface polysaccharide production. Here, we show through complementation experiments in an E. coli MG1655 hupAB double mutant strain that PG0121 encodes a functional HU homologue. Microarray and quantitative RT-PCR analysis were used to further investigate global transcriptional regulation by HUβ using comparative expression profiling of the PG0121 (HUβ) mutant strain to the parent strain, W83. Our analysis determined that expression of genes encoding proteins involved in a variety of biological functions, including iron acquisition, cell division and translation, as well as a number of predicted nucleoid associated proteins were altered in the PG0121 mutant. Phenotypic and quantitative real-time-PCR (qRT-PCR) analyses determined that under iron-limiting growth conditions, cell division and viability were defective in the PG0121 mutant. Collectively, our studies show that PG0121 does indeed encode a functional HU homologue, and HUβ has global regulatory functions in P. gingivalis; it affects not only production of capsular polysaccharides but also expression of genes involved in basic functions, such as cell wall synthesis, cell division and iron uptake.
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Affiliation(s)
- Richa Priyadarshini
- Department of Oral Medicine Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
- Department of Molecular Genetics, The Forsyth Institute, Cambridge, MA, USA
| | - Carla Cugini
- Department of Oral Medicine Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
- Department of Molecular Genetics, The Forsyth Institute, Cambridge, MA, USA
| | - Annette Arndt
- Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany
| | - Tsute Chen
- Department of Oral Medicine Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
- Department of Molecular Genetics, The Forsyth Institute, Cambridge, MA, USA
| | - Natalia O Tjokro
- Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA
| | - Steven D Goodman
- Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA
| | - Mary E Davey
- Department of Oral Medicine Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
- Department of Molecular Genetics, The Forsyth Institute, Cambridge, MA, USA
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Anuchin AM, Goncharenko AV, Demidenok OI, Kaprelyants AS. Histone-like proteins of bacteria (review). APPL BIOCHEM MICRO+ 2011. [DOI: 10.1134/s0003683811060020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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10
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HU protein affects transcription of surface polysaccharide synthesis genes in Porphyromonas gingivalis. J Bacteriol 2010; 192:6217-29. [PMID: 20889748 DOI: 10.1128/jb.00106-10] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
K-antigen capsule synthesis is an important virulence determinant of the oral anaerobe Porphyromonas gingivalis. We previously reported that the locus required for synthesis of this surface polysaccharide in strain W83 (TIGR identification PG0106 to PG0120) is transcribed as a large (∼16.7-kb) polycistronic message. Through sequence analysis, we have now identified a 77-bp inverted repeat located upstream (206 bp) of the start codon of PG0106 that is capable of forming a large hairpin structure. Further sequence analysis just upstream and downstream of the capsule synthesis genes revealed the presence of two genes oriented in the same direction as the operon that are predicted to encode DNA binding proteins: PG0104, which is highly similar (57%) to DNA topoisomerase III, and PG0121, which has high similarity (72%) to DNA binding protein HU (β-subunit). In this report, we show that these two genes, as well as the 77-bp inverted repeat region, are cotranscribed with the capsule synthesis genes, resulting in a large transcript that is ∼19.4 kb (based on annotation). We also show that a PG0121 recombinant protein is a nonspecific DNA binding protein with strong affinity to the hairpin structure, in vitro, and that transcript levels of the capsule synthesis genes are downregulated in a PG0121 deletion mutant. Furthermore, we show that this decrease in transcript levels corresponds to a decrease in the amount of polysaccharide produced. Interestingly, expression analysis of another polysaccharide synthesis locus (PG1136 to PG1143) encoding genes involved in synthesis of a surface-associated phosphorylated branched mannan (APS) indicated that this locus is also downregulated in the PG0121 mutant. Altogether our data indicate that HU protein modulates expression of surface polysaccharides in P. gingivalis strain W83.
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11
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Oberto J, Nabti S, Jooste V, Mignot H, Rouviere-Yaniv J. The HU regulon is composed of genes responding to anaerobiosis, acid stress, high osmolarity and SOS induction. PLoS One 2009; 4:e4367. [PMID: 19194530 PMCID: PMC2634741 DOI: 10.1371/journal.pone.0004367] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 12/17/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The Escherichia coli heterodimeric HU protein is a small DNA-bending protein associated with the bacterial nucleoid. It can introduce negative supercoils into closed circular DNA in the presence of topoisomerase I. Cells lacking HU grow very poorly and display many phenotypes. METHODOLOGY/PRINCIPAL FINDINGS We analyzed the transcription profile of every Escherichia coli gene in the absence of one or both HU subunits. This genome-wide in silico transcriptomic approach, performed in parallel with in vivo genetic experimentation, defined the HU regulon. This large regulon, which comprises 8% of the genome, is composed of four biologically relevant gene classes whose regulation responds to anaerobiosis, acid stress, high osmolarity, and SOS induction. CONCLUSIONS/SIGNIFICANCE The regulation a large number of genes encoding enzymes involved in energy metabolism and catabolism pathways by HU explains the highly pleiotropic phenotype of HU-deficient cells. The uniform chromosomal distribution of the many operons regulated by HU strongly suggests that the transcriptional and nucleoid architectural functions of HU constitute two aspects of a unique protein-DNA interaction mechanism.
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Affiliation(s)
- Jacques Oberto
- Laboratoire de Physiologie Bactérienne, CNRS, UPR 9073, Institut de Biologie Physico-chimique, Paris, France
- * E-mail: (JO); (JR-Y)
| | - Sabrina Nabti
- Laboratoire de Physiologie Bactérienne, CNRS, UPR 9073, Institut de Biologie Physico-chimique, Paris, France
| | - Valérie Jooste
- INSERM, UMR 866, Epidemiology and Biostatistics group, University of Dijon, Dijon, France
| | | | - Josette Rouviere-Yaniv
- Laboratoire de Physiologie Bactérienne, CNRS, UPR 9073, Institut de Biologie Physico-chimique, Paris, France
- * E-mail: (JO); (JR-Y)
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12
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Mukherjee A, Bhattacharyya G, Grove A. The C-Terminal Domain of HU-Related Histone-like Protein Hlp from Mycobacterium smegmatis Mediates DNA End-Joining. Biochemistry 2008; 47:8744-53. [DOI: 10.1021/bi800010s] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Anirban Mukherjee
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
| | - Gargi Bhattacharyya
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
| | - Anne Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
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Kamashev D, Balandina A, Mazur AK, Arimondo PB, Rouviere-Yaniv J. HU binds and folds single-stranded DNA. Nucleic Acids Res 2007; 36:1026-36. [PMID: 18096614 PMCID: PMC2241890 DOI: 10.1093/nar/gkm667] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The nucleoid-associated protein HU plays an important role in bacterial nucleoid organization and is involved in numerous processes including transposition, recombination and DNA repair. We show here that HU binds specifically DNA containing mismatched region longer than 3 bp as well as DNA bulges. HU binds single-stranded DNA (ssDNA) in a binding mode that is reminiscent but different from earlier reported specific HU interactions with double-helical DNA lesions. An HU dimer requires 24 nt of ssDNA for initial binding, and 12 nt of ssDNA for each additional dimer binding. In the presence of equimolar amounts of HU dimer and DNA, the ssDNA molecule forms an U-loop (hairpin-like) around the protein, providing contacts with both sides of the HU body. This mode differs from the binding of the single-strand-binding protein (SSB) to ssDNA: in sharp contrast to SSB, HU binds ssDNA non-cooperatively and does not destabilize double-helical DNA. Furthermore HU has a strong preference for poly(dG), while binding to poly(dA) is the weakest. HU binding to ssDNA is probably important for its capacity to cover and protect bacterial DNA both intact and carrying lesions.
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Affiliation(s)
- Dmitri Kamashev
- Laboratoire de Physiologie Bacterienne, CNRS UPR 9073, Laboratoire de Biochimie Théorique, CNRS UPR 9080, Paris, France
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Kühn K, Bohne AV, Liere K, Weihe A, Börner T. Arabidopsis phage-type RNA polymerases: accurate in vitro transcription of organellar genes. THE PLANT CELL 2007; 19:959-71. [PMID: 17400896 PMCID: PMC1867361 DOI: 10.1105/tpc.106.046839] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The T7 bacteriophage RNA polymerase (RNAP) performs all steps of transcription, including promoter recognition, initiation, and elongation as a single-polypeptide enzyme. Arabidopsis thaliana possesses three nuclear-encoded T7 phage-type RNAPs that localize to mitochondria (RpoTm), plastids (RpoTp), or presumably both organelles (RpoTmp). Their specific functions are as yet unresolved. We have established an in vitro transcription system to examine the abilities of the three Arabidopsis phage-type RNAPs to synthesize RNA and to recognize organellar promoters. All three RpoT genes were shown to encode transcriptionally active RNAPs. RpoTmp displayed no significant promoter specificity, whereas RpoTm and RpoTp were able to accurately initiate transcription from overlapping subsets of mitochondrial and plastidial promoters without the aid of protein cofactors. Our study strongly suggests RpoTm to be the enzyme that transcribes most, if not all, mitochondrial genes in Arabidopsis. Intrinsic promoter specificity, a feature that RpoTm and RpoTp share with the T7 RNAP, appears to have been conserved over the long period of evolution of nuclear-encoded mitochondrial and plastidial RNAPs. Selective promoter recognition by the Arabidopsis phage-type RNAPs in vitro implies that auxiliary factors are required for efficient initiation of transcription in vivo.
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Affiliation(s)
- Kristina Kühn
- Institute of Biology (Genetics), Humboldt University, D-10115, Berlin, Germany
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15
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Li W, Wang XS, Qu MH, Liu Y, He RQ. Human protein tau represses DNA replication in vitro. Biochim Biophys Acta Gen Subj 2005; 1726:280-6. [PMID: 16226838 DOI: 10.1016/j.bbagen.2005.08.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Revised: 08/08/2005] [Accepted: 08/19/2005] [Indexed: 01/13/2023]
Abstract
Here, in the experiments of both PCR and real-time PCR, a repression of DNA amplification was observed in the presence of protein tau. Furthermore, a strong repression appeared when an in vitro DNA replication assay was performed at the physiological temperature (37 degrees C). The incorporation of dNTP was markedly decreased to approximately 12% of control by the presence of tau23 and to approximately 15% by tau40. In the competitive experiments, the PCR product could be restored when the competitor DNA was added, indicating that the association of tau with the template gave rise to the repression. However, tau did not repress the yield of RNA in transcription, suggesting that tau was replaced or ejected from the template by the elongating T7 RNA polymerase.
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Affiliation(s)
- Wen Li
- The State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China
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16
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Preobrajenskaya OV, Starodubova ES, Karpov VL, Rouviere-Yaniv J. Comparison of the Local Concentration of the HU Protein for Particular Regions of Genomic DNA in Escherichia coli Cells in Vivo. Mol Biol 2005. [DOI: 10.1007/s11008-005-0074-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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17
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Travers A, Muskhelishvili G. DNA supercoiling — a global transcriptional regulator for enterobacterial growth? Nat Rev Microbiol 2005; 3:157-69. [PMID: 15685225 DOI: 10.1038/nrmicro1088] [Citation(s) in RCA: 244] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A fundamental principle of exponential bacterial growth is that no more ribosomes are produced than are necessary to support the balance between nutrient availability and protein synthesis. Although this conclusion was first expressed more than 40 years ago, a full understanding of the molecular mechanisms involved remains elusive and the issue is still controversial. There is currently agreement that, although many different systems are undoubtedly involved in fine-tuning this balance, an important control, and in our opinion perhaps the main control, is regulation of the rate of transcription initiation of the stable (ribosomal and transfer) RNA transcriptons. In this review, we argue that regulation of DNA supercoiling provides a coherent explanation for the main modes of transcriptional control - stringent control, growth-rate control and growth-phase control - during the normal growth of Escherichia coli.
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Affiliation(s)
- Andrew Travers
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
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van Noort J, Verbrugge S, Goosen N, Dekker C, Dame RT. Dual architectural roles of HU: formation of flexible hinges and rigid filaments. Proc Natl Acad Sci U S A 2004; 101:6969-74. [PMID: 15118104 PMCID: PMC406450 DOI: 10.1073/pnas.0308230101] [Citation(s) in RCA: 228] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The nucleoid-associated protein HU is one of the most abundant proteins in Escherichia coli and has been suggested to play an important role in bacterial nucleoid organization and regulation. Although the regulatory aspects of HU have been firmly established, much less is understood about the role of HU in shaping the bacterial nucleoid. In both functions (local) modulation of DNA architecture seems an essential feature, but information on the mechanical properties of this type of sequence-independent nucleoprotein complex is scarce. In this study we used magnetic tweezers and atomic force microscopy to quantify HU-induced DNA bending and condensation. Both techniques revealed that HU can have two opposing mechanical effects depending on the protein concentration. At concentrations <100 nM, individual HU dimers induce very flexible bends in DNA that are responsible for DNA compaction up to 50%. At higher HU concentrations, a rigid nucleoprotein filament is formed in which HU appears to arrange helically around the DNA without inducing significant condensation.
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Affiliation(s)
- John van Noort
- Molecular Biophysics, Kavli Institute of Nanoscience, Delft University of Technology, NL-2628 CJ, Delft, The Netherlands.
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Abstract
Histone-like proteins in bacteria contribute to the control of gene expression, as well as participating in other DNA transactions such as recombination and DNA replication. They have also been described, somewhat vaguely, as contributors to the organization of the bacterial nucleoid. Our view of how these proteins act in the cell is becoming clearer, particularly in the cases of Fis, H-NS and HU, three of the most intensively studied members of the group. Especially helpful have been studies of the contributions of these proteins to the regulation of specific genes such as the gal operon, and genes coding for stable RNA species, topoisomerases, and the histone-like proteins themselves. Recent advances have also been assisted by insights into the effects the histone-like proteins exert on DNA structure not only at specific promoters but throughout the genome.
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Affiliation(s)
- Charles J Dorman
- Department of Microbiology, Moyne Institute of Preventive Medicine, University of Dublin, Trinity College, Dublin 2, Ireland.
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Crucitti P, Abril AM, Salas M. Bacteriophage phi 29 early protein p17. Self-association and hetero-association with the viral histone-like protein p6. J Biol Chem 2003; 278:4906-11. [PMID: 12480935 DOI: 10.1074/jbc.m210289200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gene 17 of the Bacillus subtilis phage Phi29 is expressed early after infection, and it has been shown to be required at the very beginning of phage replication under conditions of low but not high multiplicity of infection. It has been proposed that, at the beginning of the infection, protein p17 could be recruiting limiting amounts of initiation factors at the viral origins. Once the infection process is established and the replication proteins reach optimal concentration, protein p17 becomes dispensable. In this paper we focused, on the one hand, on the study of protein p17 dimerization and the role of a putative coiled-coil region. On the other hand, we focused on its interaction with the viral origin-binding protein p6. Based on our results we propose that protein p17 function is to optimize binding of protein p6 at the viral DNA ends, thus favoring the initiation of replication and negatively modulating its own transcription.
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Affiliation(s)
- Paola Crucitti
- Centro de Biologia Molecular Severo Ochoa (CSIC-UAM), Universidad Autonoma, Canto Blanco, 28049 Madrid, Spain
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Abstract
The role of HU in Escherichia coli as both a protein involved in DNA compaction and as a protein with regulatory function seems to be firmly established. However, a critical look at the available data reveals that this is not true for each of the proposed roles of this protein. The role of HU as a regulatory or accessory protein in a number of systems has been thoroughly investigated and in many cases has been largely elucidated. However, almost 30 years after its discovery, convincing evidence for the proposed role of HU in DNA compaction is still lacking. Here we present an extensive literature survey of the available data which, in combination with novel microscopic insights, suggests that the role of HU could be the opposite as well. The protein is likely to play an architectural role, but instead of being responsible for DNA compaction it could be involved in antagonising compaction by other proteins such as H-NS.
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Affiliation(s)
- Remus Thei Dame
- Laboratory of Molecular Genetics, Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
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