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Nguyen HT, Mulero MC, Huang D, Ethayathulla AS, Ramos A, Viadiu H, Ghosh G. Challenges and Insights in Regulation of p53 and NF‐kappaB Transcription Factors: Making the Case for Cancer Prevention from the Environmental‐Physiological Paradigm. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.648.22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - DeBin Huang
- Chemistry and BiochemistryUniversity of California San DiegoLa JollaCA
| | - Abdul S. Ethayathulla
- Cell Physiology and Molecular BiophysicsTexas Tech University Health Sciences CenterLubbockTX
| | - Ana Ramos
- Research Institute of Molecular PathologyViennaAustria
| | - Hector Viadiu
- Institute of ChemistryUniversidad Nacional Autónoma de MéxicoMexico CityMexico
| | - Gourisankar Ghosh
- Chemistry and BiochemistryUniversity of California San DiegoLa JollaCA
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2
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Ramos A, Tse PW, Wang J, Ethayathulla AS, Viadiu H. Sequence Variation in the Response Element Determines Binding by the Transcription Factor p73. Biochemistry 2015; 54:6961-72. [PMID: 26529454 DOI: 10.1021/acs.biochem.5b00152] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
How the sequence of a response element affects the binding of a transcription factor and, ultimately, the differential rate of transcription of genes under its control is not well-understood. In the case of the p73 transcription factor, it binds to >200 response elements to trigger developmental, cell arrest, and apoptotic pathways. The p73 response elements match the 20 bp consensus sequence of the p53 response elements that are formed by two 10 bp half-sites, where each half-site is an inverted repeat of two 5 bp quarter-sites. Using sedimentation velocity and fluorescence anisotropy experiments, we studied how systematic variations in the sequence of a half-site response element modify the DNA binding affinity of the p73 DNA-binding domain. We observed that each nucleotide position in the response element has a different influence in determining the binding of the p73 DNA-binding domain. The cytosine in the fourth position of each quarter-site is the largest determinant of DNA binding, followed by the nucleotide in the fifth position, and last, the first three positions show a slight regulatory preference for purines. Together with previous structural and functional results, our data suggest a hierarchical model of binding in which some nucleotide positions in the response element are more important than others in determining the binding of the transcription factor.
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Affiliation(s)
- Ana Ramos
- Instituto de Química, Universidad Nacional Autónoma de México (UNAM) , Circuito Exterior, Ciudad Universitaria, Mexico City, D.F. 04510, Mexico
| | - Pui-Wah Tse
- Instituto de Química, Universidad Nacional Autónoma de México (UNAM) , Circuito Exterior, Ciudad Universitaria, Mexico City, D.F. 04510, Mexico
| | - Jessie Wang
- Instituto de Química, Universidad Nacional Autónoma de México (UNAM) , Circuito Exterior, Ciudad Universitaria, Mexico City, D.F. 04510, Mexico
| | - Abdul S Ethayathulla
- Instituto de Química, Universidad Nacional Autónoma de México (UNAM) , Circuito Exterior, Ciudad Universitaria, Mexico City, D.F. 04510, Mexico
| | - Hector Viadiu
- Instituto de Química, Universidad Nacional Autónoma de México (UNAM) , Circuito Exterior, Ciudad Universitaria, Mexico City, D.F. 04510, Mexico
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3
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Abstract
The design of a broad-spectrum cancer drug would provide enormous clinical benefits to treat cancer patients. Most of cancerous cells have a mutation in the p53 gene that results in an inactive mutant p53 protein. For this reason, p53 is a prime target for the development of a broad-spectrum cancer drug. To provide the atomic information to rationally design a drug to recover p53 activity is the main goal of the structural studies on mutant p53. We review three mechanisms that influence p53 activity and provide information about how reactivation of mutant p53 can be achieved: stabilization of the active conformation of the DNA-binding domain of the protein, suppression of missense mutations in the DNA-binding domain by a second-site mutation, and increased transactivation.
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Affiliation(s)
- Hector Viadiu
- Instituto de Química, Universidad Nacional Autónoma de México (UNAM), Mexico City, D.F., Mexico,
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Ciribilli Y, Monti P, Bisio A, Nguyen HT, Ethayathulla AS, Ramos A, Foggetti G, Menichini P, Menendez D, Resnick MA, Viadiu H, Fronza G, Inga A. Transactivation specificity is conserved among p53 family proteins and depends on a response element sequence code. Nucleic Acids Res 2013; 41:8637-53. [PMID: 23892287 PMCID: PMC3794606 DOI: 10.1093/nar/gkt657] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Structural and biochemical studies have demonstrated that p73, p63 and p53 recognize DNA with identical amino acids and similar binding affinity. Here, measuring transactivation activity for a large number of response elements (REs) in yeast and human cell lines, we show that p53 family proteins also have overlapping transactivation profiles. We identified mutations at conserved amino acids of loops L1 and L3 in the DNA-binding domain that tune the transactivation potential nearly equally in p73, p63 and p53. For example, the mutant S139F in p73 has higher transactivation potential towards selected REs, enhanced DNA-binding cooperativity in vitro and a flexible loop L1 as seen in the crystal structure of the protein–DNA complex. By studying, how variations in the RE sequence affect transactivation specificity, we discovered a RE-transactivation code that predicts enhanced transactivation; this correlation is stronger for promoters of genes associated with apoptosis.
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Affiliation(s)
- Yari Ciribilli
- Laboratory of Transcriptional Networks, Centre for Integrative Biology (CIBIO), University of Trento, TN, 38060 Italy, Molecular Mutagenesis and DNA Repair Unit, IRCSS Azienda Ospedaliera Universitaria San Martino-IST-Istituto Nazionale per la Ricerca sul Cancro, Genoa 16132, Italy, Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, 92093, USA and Chromosome Stability Group, Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, NIEHS, NIH, RTP, NC, 27709, USA
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5
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Ciribilli Y, Monti P, Bisio A, Nguyen HT, Ethayathulla AS, Resnick MA, Viadiu H, Fronza G, Inga A. Abstract 2316: Mutations in the p53 gene family reveal conservation of structure-function in the L1 and L3 loops and a response element code for transcriptional specificity. Cancer Res 2013. [DOI: 10.1158/1538-7445.am2013-2316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
The p53, p63 and p73 family of sequence-specific transcription factors share similar biochemical properties and structural features resulting in the recognition of DNA with identical amino acids and similar binding affinity. However, loss of individual members results in very different phenotypes in mice as well as humans. We have addressed functional relationships between p53 family proteins using a combination of mutants, target response elements (REs) and sequence-specific transactivation assays based in yeast and human cells. p53 alleles exhibiting enhanced transcriptional activation and altered promoter selectivity were previously identified in the L1 and L3 loop of the DNA binding domain of the protein. Included was S121F that results in defective p21 induction and confers a strong apoptotic phenotype in mammalian cells. Guided by result with p53-S121F, -T123A and -S240N mutants, the corresponding p63 and p73 alleles were investigated for ability to drive transactivation at over fifty p53 REs in isogenic yeast reporter strains. The phenotypes observed with p53 alleles were reproduced with the p63- and p73- alleles. Focusing on p73-S139F (corresponding to p53-S121F) transactivation at many RE sequences, we identify and experimentally confirm an RE target sequence code that predicts enhanced or reduced transactivation potentials. The correlation is particularly strong for induction at p53 targets within promoters of genes associated with apoptosis. Furthermore, p73 S139F showed an enhanced DNA-binding cooperativity in vitro, and loop L1 shows conformational changes in the crystal structure of the protein-DNA complex. The altered function phenotype was confirmed not only in gene reporter assays but also for endogenous gene expression in the p53 null HCT116 human cell line, suggesting that target recognition can predict relative changes in transcription rates at different loci. Based on the correlation between RE code and associated gene functions, we propose the selection during evolution of an RE sequence code within target promoters that can affect intrinsic conformational flexibility / DNA binding affinity of p53 proteins thereby modulating in vivo selectivity, specifically favoring the activation of apoptotic target genes
Citation Format: Yari Ciribilli, Paola Monti, Alessandra Bisio, H. T. Nguyen, A S. Ethayathulla, Micheal A. Resnick, Hector Viadiu, Gilberto Fronza, Alberto Inga. Mutations in the p53 gene family reveal conservation of structure-function in the L1 and L3 loops and a response element code for transcriptional specificity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2316. doi:10.1158/1538-7445.AM2013-2316
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Affiliation(s)
| | - Paola Monti
- 2Azienda Ospedaliera Universitaria San Martino-IST-Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy
| | | | - H. T. Nguyen
- 33Department of Chemistry and Biochemistry, University of California San Diego (UCSD), San Diego, CA
| | - A S. Ethayathulla
- 33Department of Chemistry and Biochemistry, University of California San Diego (UCSD), San Diego, CA
| | - Micheal A. Resnick
- 4National Institute of Environmental Health Sciences, Research Triangle Park, NC
| | - Hector Viadiu
- 33Department of Chemistry and Biochemistry, University of California San Diego (UCSD), San Diego, CA
| | - Gilberto Fronza
- 2Azienda Ospedaliera Universitaria San Martino-IST-Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy
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Monti P, Russo D, Bocciardi R, Foggetti G, Menichini P, Divizia MT, Lerone M, Graziano C, Wischmeijer A, Viadiu H, Ravazzolo R, Inga A, Fronza G. EEC- and ADULT-associated TP63 mutations exhibit functional heterogeneity toward P63 responsive sequences. Hum Mutat 2013; 34:894-904. [PMID: 23463580 DOI: 10.1002/humu.22304] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 02/22/2013] [Indexed: 01/05/2023]
Abstract
TP63 germ-line mutations are responsible for a group of human ectodermal dysplasia syndromes, underlining the key role of P63 in the development of ectoderm-derived tissues. Here, we report the identification of two TP63 alleles, G134V (p.Gly173Val) and insR155 (p.Thr193_Tyr194insArg), associated to ADULT and EEC syndromes, respectively. These alleles, along with previously identified G134D (p.Gly173Asp) and R204W (p.Arg243Trp), were functionally characterized in yeast, studied in a mammalian cell line and modeled based on the crystal structure of the P63 DNA-binding domain. Although the p.Arg243Trp mutant showed both complete loss of transactivation function and ability to interfere over wild-type P63, the impact of p.Gly173Asp, p.Gly173Val, and p.Thr193_Tyr194insArg varied depending on the response element (RE) tested. Interestingly, p.Gly173Asp and p.Gly173Val mutants were characterized by a severe defect in transactivation along with interfering ability on two DN-P63α-specific REs derived from genes closely related to the clinical manifestations of the TP63-associated syndromes, namely PERP and COL18A1. The modeling of the mutations supported the distinct functional effect of each mutant. The present results highlight the importance of integrating different functional endpoints that take in account the features of P63 proteins' target sequences to examine the impact of TP63 mutations and the associated clinical variability.
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Affiliation(s)
- Paola Monti
- Molecular Mutagenesis and DNA Repair Unit, Istituto di Ricerca e Cura a Carattere Scientifico Azienda Ospedaliera Universitaria San Martino-IST-Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy
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Ethayathulla AS, Nguyen HT, Viadiu H. Crystal structures of the DNA-binding domain tetramer of the p53 tumor suppressor family member p73 bound to different full-site response elements. J Biol Chem 2012; 288:4744-54. [PMID: 23243311 DOI: 10.1074/jbc.m112.408039] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
How cells choose between developmental pathways remains a fundamental biological question. In the case of the p53 protein family, its three transcription factors (p73, p63, and p53) each trigger a gene expression pattern that leads to specific cellular pathways. At the same time, these transcription factors recognize the same response element (RE) consensus sequences, and their transactivation of target genes overlaps. We aimed to understand target gene selectivity at the molecular level by determining the crystal structures of the p73 DNA-binding domain (DBD) in complex with full-site REs that vary in sequence. We report two structures of the p73 DBD bound as a tetramer to 20-bp full-site REs based on two distinct quarter-sites: GAACA and GAACC. Our study confirms that the DNA-binding residues are conserved within the p53 family, whereas the dimerization and tetramerization interfaces diverge. Moreover, a conserved lysine residue in loop L1 of the DBD senses the presence of guanines in positions 2 and 3 of the quarter-site RE, whereas a conserved arginine in loop 3 adapts to changes in position 5. Sequence variations in the RE elicit a p73 conformational response that might explain target gene specificity.
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Affiliation(s)
- Abdul S Ethayathulla
- Laboratory of Structural Biochemistry, Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA
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8
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Abstract
p53 is a tetrameric multidomain protein that triggers the anticancer cellular response to stress. We have calculated a three-dimensional reconstruction of full-length human p53 in the absence of DNA using single-particle electron microscopy. The reconstruction of DNA-free full-length p53 shows a square-shaped structure with four distinct domains and a hollow center. In comparison with the known compacted DNA-bound full-length p53 structures, the DNA-free p53 tetramer adopts a relaxed conformation with separated monomers and oligomerization interfaces different from those of the DNA-bound conformation.
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Affiliation(s)
- Nam Pham
- Laboratory of Structural Biochemistry, Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, MC 0378, La Jolla, CA 92093, USA
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9
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Abstract
It is challenging to find membrane mimics that stabilize the native structures, dynamics, and functions of membrane proteins. In a recent advance, nanodiscs have been shown to provide a bilayer environment compatible with solution NMR. We show that increasing the lipid to "belt" peptide ratio expands their diameter, slows their reorientation rate, and allows the protein-containing discs to be aligned in a magnetic field for oriented sample solid-state NMR. The spectroscopic properties of membrane proteins with one to seven transmembrane helices in q = 0.1 isotropic bicelles, ~10 nm diameter isotropic nanodiscs, ~30 nm diameter magnetically aligned macrodiscs, and q = 5 magnetically aligned bicelles are compared.
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Affiliation(s)
- Sang Ho Park
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0307, United States
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10
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Vanamee ES, Viadiu H, Chan SH, Ummat A, Hartline AM, Xu SY, Aggarwal AK. Asymmetric DNA recognition by the OkrAI endonuclease, an isoschizomer of BamHI. Nucleic Acids Res 2010; 39:712-9. [PMID: 20833632 PMCID: PMC3025578 DOI: 10.1093/nar/gkq779] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Restriction enzymes share little or no sequence homology with the exception of isoschizomers, or enzymes that recognize and cleave the same DNA sequence. We present here the structure of a BamHI isoschizomer, OkrAI, bound to the same DNA sequence (TATGGATCCATA) as that cocrystallized with BamHI. We show that OkrAI is a more minimal version of BamHI, lacking not only the N- and C-terminal helices but also an internal 310 helix and containing β-strands that are shorter than those in BamHI. Despite these structural differences, OkrAI recognizes the DNA in a remarkably similar manner to BamHI, including asymmetric contacts via C-terminal ‘arms’ that appear to ‘compete’ for the minor groove. However, the arms are shorter than in BamHI. We observe similar DNA-binding affinities between OkrAI and BamHI but OkrAI has higher star activity (at 37°C) compared to BamHI. Together, the OkrAI and BamHI structures offer a rare opportunity to compare two restriction enzymes that work on exactly the same DNA substrate.
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Affiliation(s)
- Eva Scheuring Vanamee
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, NY 10029, USA
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12
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Abstract
Aquaporin-9, an aquaglyceroporin present in diverse tissues, is unique among aquaporins because it is not only permeable to water, urea and glycerol, but also allows passage of larger uncharged solutes. Single particle analysis of negatively stained recombinant rat aquaporin-9 revealed a particle size characteristic of the tetrameric organization of all members of the aquaporin family. Reconstitution of aquaporin-9 into two-dimensional crystals enabled us to calculate a projection map at 7 A resolution. The projection structure indicates a tetrameric structure, similar to GlpF, with each square-like monomer forming a pore. A comparison of the pore-lining residues between the crystal structure of GlpF and a homology model of aquaporin-9 locates substitutions in these residues predominantly to the hydrophobic edge of the tripathic pore of GlpF, providing first insights into the structural basis for the broader substrate specificity of aquaporin-9.
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Affiliation(s)
- Hector Viadiu
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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13
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Vanamee ÉS, Viadiu H, Kucera R, Dorner L, Picone S, Schildkraut I, Aggarwal AK. A view of consecutive binding events from structures of tetrameric endonuclease SfiI bound to DNA. EMBO J 2005; 24:4198-208. [PMID: 16308566 PMCID: PMC1356319 DOI: 10.1038/sj.emboj.7600880] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2005] [Accepted: 10/28/2005] [Indexed: 11/09/2022] Open
Abstract
Many reactions in cells proceed via the sequestration of two DNA molecules in a synaptic complex. SfiI is a member of a growing family of restriction enzymes that can bind and cleave two DNA sites simultaneously. We present here the structures of tetrameric SfiI in complex with cognate DNA. The structures reveal two different binding states of SfiI: one with both DNA-binding sites fully occupied and the other with fully and partially occupied sites. These two states provide details on how SfiI recognizes and cleaves its target DNA sites, and gives insight into sequential binding events. The SfiI recognition sequence (GGCCNNNN[downward arrow]NGGCC) is a subset of the recognition sequence of BglI (GCCNNNN[downward arrow]NGGC), and both enzymes cleave their target DNAs to leave 3-base 3' overhangs. We show that even though SfiI is a tetramer and BglI is a dimer, and there is little sequence similarity between the two enzymes, their modes of DNA recognition are unusually similar.
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Affiliation(s)
- Éva Scheuring Vanamee
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY, USA
| | - Hector Viadiu
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY, USA
| | | | | | | | | | - Aneel K Aggarwal
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY, USA
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY 10029, USA. Tel.: +1 212 659 8647; Fax: +1 212 849 2456; E-mail:
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14
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Viadiu H, Stemmann O, Kirschner MW, Walz T. Domain structure of separase and its binding to securin as determined by EM. Nat Struct Mol Biol 2005; 12:552-3. [PMID: 15880121 DOI: 10.1038/nsmb935] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Accepted: 04/13/2005] [Indexed: 11/08/2022]
Abstract
After the degradation of its inhibitor securin, separase initiates chromosome segregation during the metaphase-to-anaphase transition by cleaving cohesin. Here we present a density map at a resolution of 25 A of negatively stained separase-securin complex. Based on labeling data and sequence analysis, we propose a model for the structure of separase, consisting of 26 ARM repeats, an unstructured region of 280 residues and two caspase-like domains, with securin binding to the ARM repeats.
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Affiliation(s)
- Hector Viadiu
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA
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15
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Viadiu H, Vanamee ES, Jacobson EM, Schildkraut I, Aggarwal AK. Crystallization of restriction endonuclease SfiI in complex with DNA. Acta Crystallogr D Biol Crystallogr 2003; 59:1493-5. [PMID: 12876363 DOI: 10.1107/s0907444903011910] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2003] [Accepted: 05/30/2003] [Indexed: 11/10/2022]
Abstract
The SfiI endonuclease from Streptomyces fimbriatus (EC 3.1.21.4) is a tetrameric enzyme that binds simultaneously to two recognition sites and cleaves both sites concertedly. It serves as a good model system for studying both specificity and cooperative DNA binding. Crystals of the enzyme were obtained by the hanging-drop vapor-diffusion method in complex with a 21-mer oligonucleotide. The crystals are trigonal, with unit-cell parameters a = b = 85.7, c = 202.6 A, and diffract to 2.6 A resolution on a rotating-anode X-ray generator. Preliminary X-ray analysis reveals the space group to be either P3(1)21 or P3(2)21. Interestingly, the crystals change to space group P6(1)22, with unit-cell parameters a = b = 85.5, c = 419.6 A, when the selenomethionyl (SeMet) derivative of the enzyme is co-crystallized with the same DNA. Phase information is currently being derived from this SeMet SfiI-DNA complex.
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Affiliation(s)
- Hector Viadiu
- Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY 10029, USA
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16
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Sun J, Viadiu H, Aggarwal AK, Weinstein H. Energetic and structural considerations for the mechanism of protein sliding along DNA in the nonspecific BamHI-DNA complex. Biophys J 2003; 84:3317-25. [PMID: 12719261 PMCID: PMC1302892 DOI: 10.1016/s0006-3495(03)70056-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The molecular mechanism by which DNA-binding proteins find their specific binding sites is still unclear. To gain insights into structural and energetic elements of this mechanism, we used the crystal structure of the nonspecific BamHI-DNA complex as a template to study the dominant electrostatic interaction in the nonspecific association of protein with DNA, and the possible sliding pathways that could be sustained by such an interaction. Based on calculations using the nonlinear Poisson-Boltzmann method and Brownian dynamics, a model is proposed for the initial nonspecific binding of BamHI to B-form DNA that differs from that seen in the crystal structure of the nonspecific complex. The model is electrostatically favorable, and the salt dependence as well as other thermodynamic parameters calculated for this model are in good agreement with experimental results. Several residues in BamHI are identified for their important contribution to the energy in the nonspecific binding model, and specific mutagenesis experiments are proposed to test the model on this basis. We show that a favorable sliding pathway of the protein along DNA is helical.
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Affiliation(s)
- Jian Sun
- Department of Physiology and Biophysics, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA
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17
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Scully KM, Jacobson EM, Jepsen K, Lunyak V, Viadiu H, Carrière C, Rose DW, Hooshmand F, Aggarwal AK, Rosenfeld MG. Allosteric effects of Pit-1 DNA sites on long-term repression in cell type specification. Science 2000; 290:1127-31. [PMID: 11073444 DOI: 10.1126/science.290.5494.1127] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Reciprocal gene activation and restriction during cell type differentiation from a common lineage is a hallmark of mammalian organogenesis. A key question, then, is whether a critical transcriptional activator of cell type-specific gene targets can also restrict expression of the same genes in other cell types. Here, we show that whereas the pituitary-specific POU domain factor Pit-1 activates growth hormone gene expression in one cell type, the somatotrope, it restricts its expression from a second cell type, the lactotrope. This distinction depends on a two-base pair spacing in accommodation of the bipartite POU domains on a conserved growth hormone promoter site. The allosteric effect on Pit-1, in combination with other DNA binding factors, results in the recruitment of a corepressor complex, including nuclear receptor corepressor N-CoR, which, unexpectedly, is required for active long-term repression of the growth hormone gene in lactotropes.
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Affiliation(s)
- K M Scully
- Howard Hughes Medical Institute, Department of Endocrinology and Metabolism, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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18
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Abstract
Restriction endonucleases show extraordinary specificity in distinguishing specific from nonspecific DNA sequences. A single basepair change within the recognition sequence results in over a million-fold loss in activity. To understand the basis of this sequence discrimination, it is just as important to study the nonspecific complex as the specific complex. We describe here the crystallization of restriction endonuclease BamHI with several nonspecific oligonucleotides. The 11-mer, 5'-ATGAATCCATA-3', yielded cocrystals with BamHI, in the presence of low salt, that diffracted to 1.9 A with synchrotron radiation. The cocrystals belong to the space group P2(1)2(1)2(1) with unit cell dimensions of a = 114.8 A, b = 91.1 A, c = 66.4 A, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees. This success in the cocrystallization of BamHI with a nonspecific DNA provides insights for future attempts at crystallization of other nonspecific DNA-protein complexes.
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Affiliation(s)
- H Viadiu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
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19
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Abstract
The central problem faced by DNA binding proteins is how to select the correct DNA sequence from the sea of nonspecific sequences in a cell. The problem is particularly acute for bacterial restriction enzymes because cleavage at an incorrect DNA site could be lethal. To understand the basis of this selectivity, we report here the crystal structure of endonuclease BamHI bound to noncognate DNA. We show that, despite only a single base pair change in the recognition sequence, the enzyme adopts an open configuration that is on the pathway between free and specifically bound forms of the enzyme. Surprisingly, the DNA drops out of the binding cleft with a total loss of base-specific and backbone contacts. Taken together, the structure provides a remarkable snapshot of an enzyme poised for linear diffusion (rather than cleavage) along the DNA.
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Affiliation(s)
- H Viadiu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
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Abstract
Type II restriction enzymes are characterized by their remarkable specificity and simplicity. They require only divalent metals (such as Mg2+ or Mn2+) as cofactors to catalyze the hydrolysis of DNA. However, most of the structural work on endonucleases has been performed in the absence of metals, leaving unanswered questions about their mechanisms of DNA cleavage. Here we report structures of the endonuclease BamHI-DNA complex, determined in the presence of Mn2+ and Ca2+, that describe the enzyme at different stages of catalysis. Overall, the results support a two-metal mechanism of DNA cleavage for BamHI which is distinct from that of EcoRV.
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Affiliation(s)
- H Viadiu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
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Viadiu H, Osuna J, Fink AL, Soberón X. A new TEM beta-lactamase double mutant with broadened specificity reveals substrate-dependent functional interactions. J Biol Chem 1995; 270:781-7. [PMID: 7822311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Using a random combinatorial mutagenesis of TEM beta-lactamase, directed against residues potentially involved in substrate discrimination, followed by selection on third generation cephalosporins, we obtained the double mutant E104M/G238S. Additionally, by using cloning strategies and site-directed mutagenesis we constructed the individual single mutants and also the single modification E104K and the double mutant E104K/G238S, which broaden the specificity of clinically isolated TEM beta-lactamase variants. The kinetic characterization of the purified double mutant E104M/G238S and its single counterparts E104M and G238S was carried out. The single mutant E104M exhibited increased kcat values against all substrates tested. Km values remained similar to the values shown by the wild-type enzyme. The mutation at E104M was responsible for the increased hydrolysis rate against cefuroxime shown by the double mutant E104/G238S. The effect of mutation G238S varied more pronouncedly, depending on the substrate. In general, a lower Km was observed, but also a decreased kcat. The double mutant E104M/G238S exhibited a higher hydrolytic rate against cefotaxime compared with the corresponding single mutations. We observed nearly a 1000-fold greater kcat/Km for the double mutant than for the wild type. This improvement in catalysis was the consequence of increased kcat and decreased Km values. Computed contact interactions from modeling substrate complexes show reliable results only for benzylpenicillin. The modeling results with this substrate confirmed the observed enzyme activities for the different single and double mutants. Analysis of the apparent coupling energies, as calculated from the kinetic parameters of the single and double mutants, showed that the quantitative effect of a second mutation on a single mutant was either absent, additive, partially additive, or synergistic with respect to the first mutation, depending on the substrate analyzed.
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Affiliation(s)
- H Viadiu
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca
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Osuna J, Viadiu H, Fink AL, Soberón X. Substitution of Asp for Asn at position 132 in the active site of TEM beta-lactamase. Activity toward different substrates and effects of neighboring residues. J Biol Chem 1995; 270:775-80. [PMID: 7822310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Using a random, combinatorial scheme of mutagenesis directed against the conserved SDN region of TEM beta-lactamase, and selective screening in ampicillin-plates, we obtained the N132D mutant enzyme. The kinetic characterization of this mutant indicated relatively small effects compared to the wild-type. Both pK1 and pK2 for catalysis were decreased about 1 unit relative to the pK's for the wild type. This effect was predominantly due to changes in Km. In contrast to the wild-type, the pH-rate profiles of the mutant showed that Km for several side chain-containing penicillin substrates increases when the pH is above 5.5. 6-Aminopenicillanic acid, which lacks a side chain, did not show this effect. With benzylpenicillin, ampicillin, and carbenicillin, kcat for the mutant showed a similar pH dependence as the wild type. With 6-aminopenicillanic acid, kcat for the mutant was greater than that for the wild type. The nature of the 104 side chain may affect the environment of Asp132; double mutants N132D/E104X (where X can be Q or N) are unable to confer antibiotic resistance to bacterial cells. The computed contact interactions from modeling substrate complexes between benzylpenicillin or 6-aminopenicillanic acid with the N132D mutant confirmed the importance of the protonation state of residue Asp132 for the complex stability with side chain-containing substrates. The data indicate that the contact between the side chain of residue 132 and the substrate is relevant for the ground state recognition, but because of close contact with several important groups in its neighborhood, residue 132 is also indirectly involved in the catalytic step of the wild-type enzyme.
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Affiliation(s)
- J Osuna
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca
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Viadiu H, Osuna J, Fink AL, Soberón X. A New TEM β
-Lactamase Double Mutant with Broadened Specificity Reveals Substrate-dependent Functional Interactions. J Biol Chem 1995. [DOI: 10.1074/jbc.270.2.781] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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