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Cashen BA, Morse M, Rouzina I, Karpel R, Williams M. Dynamic structure of T4 gene 32 protein filaments facilitates rapid noncooperative protein dissociation. Nucleic Acids Res 2023; 51:8587-8605. [PMID: 37449435 PMCID: PMC10484735 DOI: 10.1093/nar/gkad595] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 06/26/2023] [Accepted: 07/04/2023] [Indexed: 07/18/2023] Open
Abstract
Bacteriophage T4 gene 32 protein (gp32) is a model single-stranded DNA (ssDNA) binding protein, essential for DNA replication. gp32 forms cooperative filaments on ssDNA through interprotein interactions between its core and N-terminus. However, detailed understanding of gp32 filament structure and organization remains incomplete, particularly for longer, biologically-relevant DNA lengths. Moreover, it is unclear how these tightly-bound filaments dissociate from ssDNA during complementary strand synthesis. We use optical tweezers and atomic force microscopy to probe the structure and binding dynamics of gp32 on long (∼8 knt) ssDNA substrates. We find that cooperative binding of gp32 rigidifies ssDNA while also reducing its contour length, consistent with the ssDNA helically winding around the gp32 filament. While measured rates of gp32 binding and dissociation indicate nM binding affinity, at ∼1000-fold higher protein concentrations gp32 continues to bind into and restructure the gp32-ssDNA filament, leading to an increase in its helical pitch and elongation of the substrate. Furthermore, the oversaturated gp32-ssDNA filament becomes progressively unwound and unstable as observed by the appearance of a rapid, noncooperative protein dissociation phase not seen at lower complex saturation, suggesting a possible mechanism for prompt removal of gp32 from the overcrowded ssDNA in front of the polymerase during replication.
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Affiliation(s)
- Ben A Cashen
- Department of Physics, Northeastern University, Boston, MA 02115, USA
| | - Michael Morse
- Department of Physics, Northeastern University, Boston, MA 02115, USA
| | - Ioulia Rouzina
- Department of Chemistry and Biochemistry, Center for Retroviral Research and Center for RNA Biology, Ohio State University, Columbus, OH 43210, USA
| | - Richard L Karpel
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, MD 21250, USA
| | - Mark C Williams
- Department of Physics, Northeastern University, Boston, MA 02115, USA
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2
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Sheykhhasan M, Manoochehri H, Dama P. Use of CAR T-cell for acute lymphoblastic leukemia (ALL) treatment: a review study. Cancer Gene Ther 2022; 29:1080-1096. [PMID: 34987176 PMCID: PMC9395272 DOI: 10.1038/s41417-021-00418-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 11/18/2021] [Accepted: 12/13/2021] [Indexed: 02/08/2023]
Abstract
Acute lymphoblastic leukemia (ALL) is a cancer-specific lymphoid cell. Induction and consolidation chemotherapy alone or in combination with different therapeutic approaches remain the main treatment. Although complete or partial remission of the disease can be achieved, the risk of relapse or refractory leukemia is still high. More effective and safe therapy options are yet unmet needs. In recent years' new therapeutic approaches have been widely used. Hematopoietic Stem Cell Transplantation (HSCT) presents significant limitations and the outcome of the consolidation treatment is patient dependent. Side effects such as Graft versus Host Disease (GvHD) in allogeneic hematopoietic stem cell transplantation are extremely common, therefore, using alternative methods to address these challenges for treatment seems crucial. In the last decade, T cells genetically engineered with Chimeric Antigen Receptor (CAR) treatment for the ALL are largely studied and represent the new era of strategy. According to the Phase I/II clinical trials, this technology results seem very promising and can be used in the next future as an effective and safe treatment for ALL treatment. In this review different generations, challenges, and clinical studies related to chimeric antigen receptor (CAR) T-cells for ALL treatment are discussed.
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Affiliation(s)
- Mohsen Sheykhhasan
- grid.411950.80000 0004 0611 9280Research Center for Molecular Medicine, Hamadan University of Medical Sciences, Hamadan, Iran ,Department of Mesenchymal Stem Cells, Academic Center for Education, Culture and Research, Qom, Iran
| | - Hamed Manoochehri
- grid.411950.80000 0004 0611 9280Research Center for Molecular Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Paola Dama
- Research Fellow School of Life Sciences, University of Sussex, Brighton, UK.
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3
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Israels B, Albrecht CS, Dang A, Barney M, von Hippel PH, Marcus AH. Submillisecond Conformational Transitions of Short Single-Stranded DNA Lattices by Photon Correlation Single-Molecule Förster Resonance Energy Transfer. J Phys Chem B 2021; 125:9426-9440. [PMID: 34379430 DOI: 10.1021/acs.jpcb.1c04119] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Thermally driven conformational fluctuations (or "breathing") of DNA play important roles in the function and regulation of the "macromolecular machinery of genome expression." Fluctuations in double-stranded (ds) DNA are involved in the transient exposure of pathways to protein binding sites within the DNA framework, leading to the binding of regulatory proteins to single-stranded (ss) DNA templates. These interactions often require that the ssDNA sequences, as well as the proteins involved, assume transient conformations critical for successful binding. Here, we use microsecond-resolved single-molecule Förster resonance energy transfer (smFRET) experiments to investigate the backbone fluctuations of short [oligo(dT)n] templates within DNA constructs that also serve as models for ss-dsDNA junctions. Such junctions, together with the attached ssDNA sequences, are involved in interactions with the ssDNA binding (ssb) proteins that control and integrate the functions of DNA replication complexes. We analyze these data using a chemical network model based on multiorder time-correlation functions and probability distribution functions that characterize the kinetic and thermodynamic behavior of the system. We find that the oligo(dT)n tails of ss-dsDNA constructs interconvert, on submillisecond time scales, between three macrostates with distinctly different end-to-end distances. These are (i) a "compact" macrostate that represents the dominant species at equilibrium; (ii) a "partially extended" macrostate that exists as minority species; and (iii) a "highly extended" macrostate that is present in trace amounts. We propose a model for ssDNA secondary structure that advances our understanding of how spontaneously formed nucleic acid conformations may facilitate the activities of ssDNA-associating proteins.
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Affiliation(s)
- Brett Israels
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States.,Department of Chemistry and Biochemistry, Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403, United States
| | - Claire S Albrecht
- Department of Physics, Center for Optical, Molecular and Quantum Science, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
| | - Anson Dang
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
| | - Megan Barney
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
| | - Peter H von Hippel
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
| | - Andrew H Marcus
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States.,Department of Chemistry and Biochemistry, Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403, United States.,Department of Physics, Center for Optical, Molecular and Quantum Science, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
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4
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Camel BR, Jose D, Meze K, Dang A, von Hippel P. Mapping DNA conformations and interactions within the binding cleft of bacteriophage T4 single-stranded DNA binding protein (gp32) at single nucleotide resolution. Nucleic Acids Res 2021; 49:916-927. [PMID: 33367802 PMCID: PMC7826291 DOI: 10.1093/nar/gkaa1230] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 11/28/2020] [Accepted: 12/07/2020] [Indexed: 11/29/2022] Open
Abstract
In this study, we use single-stranded DNA (oligo-dT) lattices that have been position-specifically labeled with monomer or dimer 2-aminopurine (2-AP) probes to map the local interactions of the DNA bases with the nucleic acid binding cleft of gp32, the single-stranded binding (ssb) protein of bacteriophage T4. Three complementary spectroscopic approaches are used to characterize these local interactions of the probes with nearby nucleotide bases and amino acid residues at varying levels of effective protein binding cooperativity, as manipulated by changing lattice length. These include: (i) examining local quenching and enhancing effects on the fluorescence spectra of monomer 2-AP probes at each position within the cleft; (ii) using acrylamide as a dynamic-quenching additive to measure solvent access to monomer 2-AP probes at each ssDNA position; and (iii) employing circular dichroism spectra to characterize changes in exciton coupling within 2-AP dimer probes at specific ssDNA positions within the protein cleft. The results are interpreted in part by what we know about the topology of the binding cleft from crystallographic studies of the DNA binding domain of gp32 and provide additional insights into how gp32 can manipulate the ssDNA chain at various steps of DNA replication and other processes of genome expression.
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Affiliation(s)
- Benjamin R Camel
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA
| | - Davis Jose
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA
- Department of Chemistry and Physics, Monmouth University, West Long Branch, NJ 07764, USA
| | - Katarina Meze
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA
| | - Anson Dang
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA
| | - Peter H von Hippel
- Institute of Molecular Biology and Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA
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5
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Evidence Falsifying the Double Helix Model. Symmetry (Basel) 2019. [DOI: 10.3390/sym11121445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Through more than 40 years of reading, thinking, searching, and experimentation, we have found that the double helix model carries some defects or incorrect information. Evidence gleaned from the literature clearly indicates that the two strands of DNA are coiled ambidextrously, rather than plectonemically. It is likely that the linking number of native chromosomal Escherichia coli (E. coli) DNA is less than 960. Presently, a clear voice is necessary to break the ice formed from decades of misleading media, questionable textbooks, and expediency. For the sake of science, we are responsible and willing to share our hard-earned knowledge, experience, and knack with the public. A promising research plan is provided for the additional falsification of the right-handed double helix model. It would be a precision hit at the Achilles’ heel of the double helix model. An appropriate conceptual shift will hopefully lead to new knowledge on the secondary structure of DNA and improve understanding of its biological functions.
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6
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Probing hyper-negatively supercoiled mini-circles with nucleases and DNA binding proteins. PLoS One 2018; 13:e0202138. [PMID: 30114256 PMCID: PMC6095550 DOI: 10.1371/journal.pone.0202138] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/28/2018] [Indexed: 02/08/2023] Open
Abstract
It is well accepted that the introduction of negative supercoils locally unwinds the DNA double helix, influencing thus the activity of proteins. Despite the use of recent methods of molecular dynamics simulations to model the DNA supercoiling-induced DNA deformation, the precise extent and location of unpaired bases induced by the negative supercoiling have never been investigated at the nucleotide level. Our goals in this study were to use radiolabeled double-stranded DNA mini-circles (dsMCs) to locate the unpaired bases on dsMCs whose topology ranged from relaxed to hyper-negatively supercoiled states, and to characterize the binding of proteins involved in the DNA metabolism. Our results show that the Nuclease SI is nearly ten times more active on hyper-negatively supercoiled than relaxed DNA. The structural changes responsible for this stimulation of activity were mapped for the first time with a base pair resolution and shown to be subtle and distributed along the entire sequence. As divalent cations modify the DNA topology, our binding studies were conducted with or without magnesium. Without magnesium, the dsMCs topoisomers mostly differ by their twist. Under these conditions, the Escherichia coli topoisomerase I weakly binds relaxed dsMCs and exhibits a stronger binding on negatively and hyper-negatively supercoiled dsMCs than relaxed dsMCs, with no significant difference in the binding activity among the supercoiled topoisomers. For the human replication protein A (hRPA), the more negatively supercoiled is the DNA, the better the binding, illustrating the twist-dependent binding activity for this protein. The presence of magnesium permits the dsMCs to writhe upon introduction of negative supercoiling and greatly modifies the binding properties of the hRPA and Escherichia coli SSB on dsMCs, indicating a magnesium-dependent DNA binding behavior. Finally, our experiments that probe the topology of the DNA in the hRPA-dsMC complexes show that naked and hRPA-bound dsMCs have the same topology.
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7
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Using microsecond single-molecule FRET to determine the assembly pathways of T4 ssDNA binding protein onto model DNA replication forks. Proc Natl Acad Sci U S A 2017; 114:E3612-E3621. [PMID: 28416680 DOI: 10.1073/pnas.1619819114] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DNA replication is a core biological process that occurs in prokaryotic cells at high speeds (∼1 nucleotide residue added per millisecond) and with high fidelity (fewer than one misincorporation event per 107 nucleotide additions). The ssDNA binding protein [gene product 32 (gp32)] of the T4 bacteriophage is a central integrating component of the replication complex that must continuously bind to and unbind from transiently exposed template strands during DNA synthesis. We here report microsecond single-molecule FRET (smFRET) measurements on Cy3/Cy5-labeled primer-template (p/t) DNA constructs in the presence of gp32. These measurements probe the distance between Cy3/Cy5 fluorophores that label the ends of a short (15-nt) segment of ssDNA attached to a model p/t DNA construct and permit us to track the stochastic interconversion between various protein bound and unbound states. The length of the 15-nt ssDNA lattice is sufficient to accommodate up to two cooperatively bound gp32 proteins in either of two positions. We apply a unique multipoint time correlation function analysis to the microsecond-resolved smFRET data obtained to determine and compare the kinetics of various possible reaction pathways for the assembly of cooperatively bound gp32 protein onto ssDNA sequences located at the replication fork. The results of our analysis reveal the presence and translocation mechanisms of short-lived intermediate bound states that are likely to play a critical role in the assembly mechanisms of ssDNA binding proteins at replication forks and other ss duplex junctions.
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8
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Jose D, Weitzel SE, Baase WA, von Hippel PH. Mapping the interactions of the single-stranded DNA binding protein of bacteriophage T4 (gp32) with DNA lattices at single nucleotide resolution: gp32 monomer binding. Nucleic Acids Res 2015; 43:9276-90. [PMID: 26275775 PMCID: PMC4627070 DOI: 10.1093/nar/gkv817] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Accepted: 07/31/2015] [Indexed: 12/02/2022] Open
Abstract
Combining biophysical measurements on T4 bacteriophage replication complexes with detailed structural information can illuminate the molecular mechanisms of these ‘macromolecular machines’. Here we use the low energy circular dichroism (CD) and fluorescent properties of site-specifically introduced base analogues to map and quantify the equilibrium binding interactions of short (8 nts) ssDNA oligomers with gp32 monomers at single nucleotide resolution. We show that single gp32 molecules interact most directly and specifically near the 3′-end of these ssDNA oligomers, thus defining the polarity of gp32 binding with respect to the ssDNA lattice, and that only 2–3 nts are directly involved in this tight binding interaction. The loss of exciton coupling in the CD spectra of dimer 2-AP (2-aminopurine) probes at various positions in the ssDNA constructs, together with increases in fluorescence intensity, suggest that gp32 binding directly extends the sugar-phosphate backbone of this ssDNA oligomer, particularly at the 3′-end and facilitates base unstacking along the entire 8-mer lattice. These results provide a model (and ‘DNA map’) for the isolated gp32 binding to ssDNA targets, which serves as the nucleation step for the cooperative binding that occurs at transiently exposed ssDNA sequences within the functioning T4 DNA replication complex.
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Affiliation(s)
- Davis Jose
- Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, OR 97403-1229, USA
| | - Steven E Weitzel
- Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, OR 97403-1229, USA
| | - Walter A Baase
- Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, OR 97403-1229, USA
| | - Peter H von Hippel
- Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, OR 97403-1229, USA
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9
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Interaction of Kaposi's sarcoma-associated herpesvirus ORF6 protein with single-stranded DNA. J Virol 2014; 88:8687-95. [PMID: 24850743 DOI: 10.1128/jvi.03652-13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Kaposi's sarcoma-associated herpesvirus (KSHV) ORF6 is homologous to the herpes simplex virus 1 (HSV-1) ICP8 and Epstein-Barr virus (EBV) BALF2 proteins. Here, we describe its single-stranded DNA (ssDNA) binding properties. Based on previous findings with ICP8 and BALF2, a 60-amino-acid C-terminal deletion mutant of Orf6 was generated, and the protein was purified to explore the function of the C terminus in ssDNA binding. We showed that full-length ORF6 binds cooperatively to M13 ssDNA, disrupting its secondary structure and extending it to a length equivalent to that of duplex M13 DNA. The width of the ORF6-ssDNA filament is 9 nm, and a 7.3-nm repeat can be distinguished along the filament axis. Fluorescence polarization analysis revealed that the wild-type and C-terminal mutant ORF6 proteins bind equally well to short ssDNA substrates, with dissociation constant (Kd) values of 2.2 × 10(-7)M and 1.5 × 10(-7)M, respectively. These values were confirmed by electrophoretic mobility shift assay (EMSA) analysis, which also suggested that binding by the full-length protein may involve both monomers and small multimers. While no significant difference in affinities of binding between full-length ORF6 and the C-terminal deletion mutant were observed with the short DNAs, binding of the C-terminal mutant protein to M13 ssDNA showed a clear lack of cooperativity as seen by electron microscopy (EM). Incubation of a duplex DNA containing a long single-stranded tail with double-helical ORF6 protein filaments revealed that the ssDNA segment can be enveloped within the protein filament without disrupting the filament structure. IMPORTANCE This work describes the biochemical characterization of the single-stranded DNA binding protein of KSHV, ORF6, central to viral DNA replication in infected cells. A C-terminal deletion mutant protein was generated to aid in understanding the role of the C terminus in DNA binding. Here we analyze the binding of the wild-type and mutant proteins to short oligomeric and longer genomic ssDNA substrates. Although it is capable of interacting with the short substrates, the inability of mutant ORF6 to form oligomers in solution hindered it from fully covering the long genomic substrates. We previously showed that ORF6 forms long filaments in solution, and we showed here that these can absorb ssDNA without disruption of the filament structure. This work will provide an important basis for future studies by us and/or others.
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10
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Abstract
Approximately 2% of the DNA of the mouse genome reassociates at infinitely low C 0 t values, 10(-7) to 10(-6) moles 1(-1) s. The melting profile of the reassociation product, which is resistant to nuclease S1 digestion, has been characterized by hydroxyapatite column chromatography. The properties of these nuclease resistant sequences suggest that they exist as 'DNA-hairpins' and that they originate from reverted base sequences within the genome.
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11
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Zyrina NV, Artyukh RI, Svad’bina IV, Zheleznaya LA, Matvienko NI. The effect of single-stranded DNA binding proteins on template/primer-independent DNA synthesis in the presence of nicking endonuclease Nt.BspD6I. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2012; 38:199-205. [DOI: 10.1134/s1068162012020161] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Amos-Landgraf JM, Irving AA, Hartman C, Hunter A, Laube B, Chen X, Clipson L, Newton MA, Dove WF. Monoallelic silencing and haploinsufficiency in early murine intestinal neoplasms. Proc Natl Acad Sci U S A 2012; 109:2060-5. [PMID: 22308460 PMCID: PMC3277532 DOI: 10.1073/pnas.1120753109] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Studies of tumors from human familial adenomatous polyposis, sporadic colon cancer, and mouse and rat models of intestinal cancer indicate that the majority of early adenomas develop through loss of normal function of the Adenomatous polyposis coli (APC) gene. In murine models of familial adenomatous polyposis, specifically the multiple intestinal neoplasia mouse (Min) and the polyposis in the rat colon (Pirc) rat, most adenomas have lost their WT copy of the Apc gene through loss of heterozygosity by homologous somatic recombination. We report that large colonic adenomas in the Pirc rat have no detectable copy number losses or gains in genomic material and that most tumors lose heterozygosity only on the short arm of chromosome 18. Examination of early mouse and rat tumors indicates that a substantial subset of tumors shows maintenance of heterozygosity of Apc in genomic DNA, apparently violating Knudson's two-hit hypothesis. Sequencing of the Apc gene in a sampling of rat tumors failed to find secondary mutations in the majority of tumors that maintained heterozygosity of Apc in genomic DNA. Using quantitative allele-specific assays of Apc cDNA, we discovered two neoplastic pathways. One class of tumors maintains heterozygosity of Apc(Min/+) or Apc(Pirc/+) RNA expression and may involve haploinsufficiency for Apc function. Another class of tumors exhibits highly biased monoallelic expression of the mutant Apc allele, providing evidence for a stochastic or random process of monoallelic epigenetic silencing of the tumor suppressor gene Apc.
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Affiliation(s)
| | - Amy A. Irving
- McArdle Laboratory for Cancer Research, Department of Oncology
- Molecular and Environmental Toxicology Center
| | - Cory Hartman
- McArdle Laboratory for Cancer Research, Department of Oncology
| | - Anthony Hunter
- McArdle Laboratory for Cancer Research, Department of Oncology
| | - Brianna Laube
- McArdle Laboratory for Cancer Research, Department of Oncology
| | - Xiaodi Chen
- McArdle Laboratory for Cancer Research, Department of Oncology
| | - Linda Clipson
- McArdle Laboratory for Cancer Research, Department of Oncology
| | | | - William F. Dove
- McArdle Laboratory for Cancer Research, Department of Oncology
- Laboratory of Genetics, University of Wisconsin – Madison, Madison, WI 53706
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13
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Finding of a zero linking number topoisomer. Biochim Biophys Acta Gen Subj 2009; 1790:126-33. [DOI: 10.1016/j.bbagen.2008.10.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 08/26/2008] [Accepted: 10/31/2008] [Indexed: 11/19/2022]
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14
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Wong TS, Rajagopalan S, Townsley FM, Freund SM, Petrovich M, Loakes D, Fersht AR. Physical and functional interactions between human mitochondrial single-stranded DNA-binding protein and tumour suppressor p53. Nucleic Acids Res 2008; 37:568-81. [PMID: 19066201 PMCID: PMC2632919 DOI: 10.1093/nar/gkn974] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Single-stranded DNA-binding proteins (SSB) form a class of proteins that bind preferentially single-stranded DNA with high affinity. They are involved in DNA metabolism in all organisms and serve a vital role in replication, recombination and repair of DNA. In this report, we identify human mitochondrial SSB (HmtSSB) as a novel protein-binding partner of tumour suppressor p53, in mitochondria. It binds to the transactivation domain (residues 1-61) of p53 via an extended binding interface, with dissociation constant of 12.7 (+/- 0.7) microM. Unlike most binding partners reported to date, HmtSSB interacts with both TAD1 (residues 1-40) and TAD2 (residues 41-61) subdomains of p53. HmtSSB enhances intrinsic 3'-5' exonuclease activity of p53, particularly in hydrolysing 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) present at 3'-end of DNA. Taken together, our data suggest that p53 is involved in DNA repair within mitochondria during oxidative stress. In addition, we characterize HmtSSB binding to ssDNA and p53 N-terminal domain using various biophysical measurements and we propose binding models for both.
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Affiliation(s)
- Tuck Seng Wong
- Centre for Protein Engineering, Medical Research Council, Hills Road, Cambridge CB2 0QH, UK
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15
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16
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Pant K, Shokri L, Karpel RL, Morrical SW, Williams MC. Modulation of T4 gene 32 protein DNA binding activity by the recombination mediator protein UvsY. J Mol Biol 2008; 380:799-811. [PMID: 18565541 DOI: 10.1016/j.jmb.2008.05.039] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 05/15/2008] [Accepted: 05/16/2008] [Indexed: 11/16/2022]
Abstract
Bacteriophage T4 UvsY is a recombination mediator protein that promotes assembly of the UvsX-ssDNA presynaptic filament. UvsY helps UvsX to displace T4 gene 32 protein (gp32) from ssDNA, a reaction necessary for proper formation of the presynaptic filament. Here we use DNA stretching to examine UvsY interactions with single DNA molecules in the presence and absence of gp32 and a gp32 C-terminal truncation (*I), and show that in both cases UvsY is able to destabilize gp32-ssDNA interactions. In these experiments UvsY binds more strongly to dsDNA than ssDNA due to its inability to wrap ssDNA at high forces. To support this hypothesis, we show that ssDNA created by exposure of stretched DNA to glyoxal is strongly wrapped by UvsY, but wrapping occurs only at low forces. Our results demonstrate that UvsY interacts strongly with stretched DNA in the absence of other proteins. In the presence of gp32 and *I, UvsY is capable of strongly destabilizing gp32-DNA complexes in order to facilitate ssDNA wrapping, which in turn prepares the ssDNA for presynaptic filament assembly in the presence of UvsX. Thus, UvsY mediates UvsX binding to ssDNA by converting rigid gp32-DNA filaments into a structure that can be strongly bound by UvsX.
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Affiliation(s)
- Kiran Pant
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
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17
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Probing interactions between plant virus movement proteins and nucleic acids. Methods Mol Biol 2008. [PMID: 18370264 DOI: 10.1007/978-1-59745-102-4_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Most plant viruses move between plant cells with the help of their movement proteins (MPs). MPs are multifunctional proteins, and one of their functions is almost invariably binding to nucleic acids. Presumably, the MP-nucleic acid interaction is directly involved in formation of nucleoprotein complexes that function as intermediates in the cell-to-cell transport of many plant viruses. Thus, when studying a viral MP, it is important to determine whether or not it binds nucleic acids, and to characterize the hallmark parameters of such binding, i.e., preference for single- or double-stranded nucleic acids and binding cooperativity and sequence specificity. Here, we present two major experimental approaches, native gel mobility shift assay and ultra violet (UV) light cross-linking, for detection and characterization of MP binding to DNA and RNA molecules. We also describe protocols for purification of recombinant viral MPs over-expressed in bacteria and production of different DNA and RNA probes for these binding assays.
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18
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Hecker A, Leulliot N, Gadelle D, Graille M, Justome A, Dorlet P, Brochier C, Quevillon-Cheruel S, Le Cam E, van Tilbeurgh H, Forterre P. An archaeal orthologue of the universal protein Kae1 is an iron metalloprotein which exhibits atypical DNA-binding properties and apurinic-endonuclease activity in vitro. Nucleic Acids Res 2007; 35:6042-51. [PMID: 17766251 PMCID: PMC2094082 DOI: 10.1093/nar/gkm554] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The Kae1 (Kinase-associated endopeptidase 1) protein is a member of the recently identified transcription complex EKC and telomeres maintenance complex KEOPS in yeast. Kae1 homologues are encoded by all sequenced genomes in the three domains of life. Although annotated as putative endopeptidases, the actual functions of these universal proteins are unknown. Here we show that the purified Kae1 protein (Pa-Kae1) from Pyrococcus abyssi is an iron-protein with a novel type of ATP-binding site. Surprisingly, this protein did not exhibit endopeptidase activity in vitro but binds cooperatively to single and double-stranded DNA and induces unusual DNA conformational change. Furthermore, Pa-Kae1 exhibits a class I apurinic (AP)-endonuclease activity (AP-lyase). Both DNA binding and AP-endonuclease activity are inhibited by ATP. Kae1 is thus a novel and atypical universal DNA interacting protein whose importance could rival those of RecA (RadA/Rad51) in the maintenance of genome integrity in all living cells.
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Affiliation(s)
- Arnaud Hecker
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Nicolas Leulliot
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Danièle Gadelle
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Marc Graille
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Anthony Justome
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Pierre Dorlet
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Céline Brochier
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Sophie Quevillon-Cheruel
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Eric Le Cam
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Herman van Tilbeurgh
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Patrick Forterre
- Institut de Génétique et Microbiologie, Univ. Paris-Sud, IFR115, UMR8621-CNRS, 91405 Orsay, France, Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Univ. Paris-Sud, IFR115, UMR8619-CNRS, 91405 Orsay, France, Institut Gustave Roussy, Interactions Moléculaires et Cancer, UMR8126-CNRS, 94805 Villejuif Cedex, France, Institut de Chimie Moléculaire et des Matériaux, Univ. Paris-Sud, UMR8182-CNRS, 91405 Orsay, France, Institut de Biologie Structurale et de Microbiologie, Laboratoire de Chimie Bactérienne, UPR9043-CNRS, 13402 Marseille Cedex 20, France, Université de Provence - Aix-Marseille I, 13331 Marseille Cedex 3, France and Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
- *To whom correspondence should be addressed. +33 1 69 15 74 89+33 1 69 15 78 08 Correspondence may also be addressed to Herman van Tilbeurgh.
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Hamon L, Pastré D, Dupaigne P, Le Breton C, Le Cam E, Piétrement O. High-resolution AFM imaging of single-stranded DNA-binding (SSB) protein--DNA complexes. Nucleic Acids Res 2007; 35:e58. [PMID: 17392343 PMCID: PMC1885666 DOI: 10.1093/nar/gkm147] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
DNA in living cells is generally processed via the generation and the protection of single-stranded DNA involving the binding of ssDNA-binding proteins (SSBs). The studies of SSB-binding mode transition and cooperativity are therefore critical to many cellular processes like DNA repair and replication. However, only a few atomic force microscopy (AFM) investigations of ssDNA nucleoprotein filaments have been conducted so far. The point is that adsorption of ssDN A–SSB complexes on mica, necessary for AFM imaging, is not an easy task. Here, we addressed this issue by using spermidine as a binding agent. This trivalent cation induces a stronger adsorption on mica than divalent cations, which are commonly used by AFM users but are ineffective in the adsorption of ssDNA–SSB complexes. At low spermidine concentration (<0.3 mM), we obtained AFM images of ssDNA–SSB complexes (E. coli SSB, gp32 and yRPA) on mica at both low and high ionic strengths. In addition, partially or fully saturated nucleoprotein filaments were studied at various monovalent salt concentrations thus allowing the observation of SSB-binding mode transition. In association with conventional biochemical techniques, this work should make it possible to study the dynamics of DNA processes involving DNA–SSB complexes as intermediates by AFM.
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Affiliation(s)
- Loïc Hamon
- Laboratoire de Structure et Activité des Biomolécules Normales et Pathologiques, INSERM U829, Université d'Evry-Val d'Essonne EA3637, Evry, F-91025, France.
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20
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Vollenweider HJ. Visual biochemistry: new insight into structure and function of the genome. METHODS OF BIOCHEMICAL ANALYSIS 2006; 28:201-65. [PMID: 6178943 DOI: 10.1002/9780470110485.ch5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Mirambeau G, Lyonnais S, Coulaud D, Hameau L, Lafosse S, Jeusset J, Justome A, Delain E, Gorelick RJ, Le Cam E. Transmission electron microscopy reveals an optimal HIV-1 nucleocapsid aggregation with single-stranded nucleic acids and the mature HIV-1 nucleocapsid protein. J Mol Biol 2006; 364:496-511. [PMID: 17020765 DOI: 10.1016/j.jmb.2006.08.065] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Accepted: 08/14/2006] [Indexed: 11/19/2022]
Abstract
HIV-1 nucleocapsid protein (NCp7) condenses the viral RNA within the mature capsid. In a capsid-free system, NCp7 promotes an efficient mechanism of aggregation with both RNA and DNA. Here, we show an analysis of these macromolecular complexes by dark-field imaging using transmission electron microscopy. Thousands of mature NCp7 proteins co-aggregate with hundreds of single-stranded circular DNA molecules (ssDNA) within minutes, as observed with poly(rA). These co-aggregates are highly stable but dynamic structures, as they dissociate under harsh conditions, and after addition of potent ssDNA or NCp7 competitive ligands. The N-terminal domain and zinc fingers of NCp7 are both required for efficient association. Addition of magnesium slightly increases the avidity of NCp7 for ssDNA, while it strongly inhibits co-aggregation with relaxed circular double-stranded DNA (dsDNA). This DNA selectivity is restricted to mature NCp7, compared to its precursors NCp15 and NCp9. Moreover, for NCp15, the linkage of NCp7 with the Gag C-terminal p6-peptide provokes a deficiency in ssDNA aggregation, but results in DNA spreading similar to prototypical SSB proteins. Finally, this co-aggregation is discussed in a dynamic architectural context with regard to the mature HIV-1 nucleocapsid. On the basis of the present data, we propose that condensation of encapsidated RNA requires the C-terminal processing of NCp. Subsequently, disassembly of the nucleocapsid should be favoured once dsDNA is produced by HIV-1 reverse transcriptase.
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Affiliation(s)
- Gilles Mirambeau
- Laboratoire de Microscopie Moléculaire et Cellulaire, CNRS UMR 8126, Institut Gustave Roussy, 94805 Villejuif, France.
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Chastain PD, Makhov AM, Nossal NG, Griffith J. Architecture of the replication complex and DNA loops at the fork generated by the bacteriophage t4 proteins. J Biol Chem 2003; 278:21276-85. [PMID: 12649286 DOI: 10.1074/jbc.m301573200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rolling circle replication has previously been reconstituted in vitro using M13 duplex circles containing preformed forks and the 10 purified T4 bacteriophage replication proteins. Leading and lagging strand synthesis in these reactions is coupled and the size of the Okazaki fragments produced is typical of those generated in T4 infections. In this study the structure of the DNAs and DNA-protein complexes engaged in these in vitro reactions has been examined by electron microscopy. Following deproteinization, circular duplex templates with linear tails as great as 100 kb are observed. The tails are fully duplex except for one to three single-stranded DNA segments close to the fork. This pattern reflects Okazaki fragments stopped at different stages in their synthesis. Examination of the DNA-protein complexes in these reactions reveals M13 duplex circles in which 64% contain a single large protein mass (replication complex) and a linear duplex tail. In 56% of the replicating molecules with a tail there is at least one fully duplex loop at the replication complex resulting from the portion of the lagging strand engaged in Okazaki fragment synthesis folding back to the replisome. The single-stranded DNA segments at the fork bound by gene 32 and 59 proteins are not extended but rather appear organized into highly compact structures ("bobbins"). These bobbins constitute a major portion of the mass of the full replication complex.
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Affiliation(s)
- Paul D Chastain
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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24
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Sweezy MA, Morrical SW. Biochemical interactions within a ternary complex of the bacteriophage T4 recombination proteins uvsY and gp32 bound to single-stranded DNA. Biochemistry 1999; 38:936-44. [PMID: 9893989 DOI: 10.1021/bi9817055] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The presynaptic phase of homologous recombination requires the formation of a filament of single-stranded DNA (ssDNA) coated with a recombinase enzyme. In bacteriophage T4, at least three proteins are required for the assembly of this presynaptic filament. In addition to the T4 recombinase, uvsX protein, the T4 ssDNA binding protein (gp32), and the uvsY recombination accessory protein are also required. Here we report on a detailed analysis of a tripartite filament containing ssDNA bound by stoichiometric quantities of both uvsY and gp32, which appears to be an important intermediate in the assembly of the T4 presynaptic filament. We demonstrate that uvsY and gp32 simultaneously co-occupy the ssDNA in a noncompetitive fashion. In addition, we show that protein-protein interactions between uvsY and gp32 are not required for the assembly of this ternary complex and do not affect the affinity of uvsY for the ssDNA lattice. Finally, we demonstrate that the interaction of gp32 with the ssDNA is destabilized within this complex, in a manner which is independent of gp32-uvsY interactions. The data suggest that the uvsY protein acts to remodel the gp32-ssDNA complex via uvsY-ssDNA interactions. The implications of these findings for the mechanism of presynapsis in the T4 recombination system are discussed.
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Affiliation(s)
- M A Sweezy
- Department of Biochemistry, Vermont Cancer Center, University of Vermont College of Medicine, Burlington 05405, USA
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Le Cam E, Coulaud D, Delain E, Petitjean P, Roques BP, Gérard D, Stoylova E, Vuilleumier C, Stoylov SP, Mély Y. Properties and growth mechanism of the ordered aggregation of a model RNA by the HIV-1 nucleocapsid protein: an electron microscopy investigation. Biopolymers 1998; 45:217-29. [PMID: 9465785 DOI: 10.1002/(sici)1097-0282(199803)45:3<217::aid-bip4>3.0.co;2-u] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
NCp7, the nucleocapsid protein of the human immunodeficiency virus type 1, induces an ordered aggregation of RNAs, a mechanism that is thought to be involved in the NCp7-induced promotion of nucleic acid annealing. To further investigate this aggregation the morphology and the properties of the NCp7-induced aggregates of the model RNA homoribopolymer, polyA, were investigated by electron microscopy in various conditions. In almost all the tested conditions, the aggregates were spherical and consisted of a central dense core surrounded by a less dense halo made of NCp7-covered polyA molecules. The formation of these aggregates with a narrow distribution of sizes constitutes a distinctive feature of NCp7 over other single-stranded nucleic acid binding proteins. In most conditions, at the shortest times that can be reached experimentally, all the polyA molecules were already incorporated in small aggregates, suggesting that the nucleation step and the first aggregation events took place rapidly. The aggregates then orderly grew with time by fusion of the smaller aggregates to give larger ones. The aggregate halo was important in the fusion process by initiating the bridging between the colliding aggregates. In the presence of an excess of protein, the aggregates grew rapidly but were loosely packed and dissociated easily, suggesting adverse protein-protein interactions in the aggregates obtained in these conditions. In the presence of an excess of nucleotides, the presence of both amorphous nonspherical and slowly growing spherical aggregates suggested some changes in the mechanism of aggregate growth due to an incomplete covering of polyA molecules by NCp7. Finally, we showed that in the absence of added salt, the aggregate fusions were unfavored but not the initial events giving the first aggregates, the reverse being true in the presence of high salt concentrations (> or = 300 mM).
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Affiliation(s)
- E Le Cam
- Laboratoire de microscopie cellulaire et moléculaire, URA 147 du Centre National de la Recherche Scientifique (CNRS), Institut Gustave Roussy, Villejuif, France
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Wright WE, Tesmer VM, Huffman KE, Levene SD, Shay JW. Normal human chromosomes have long G-rich telomeric overhangs at one end. Genes Dev 1997; 11:2801-9. [PMID: 9353250 PMCID: PMC316649 DOI: 10.1101/gad.11.21.2801] [Citation(s) in RCA: 571] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Telomeres protect the ends of linear chromosomes from degradation and abnormal recombination events, and in vertebrates may be important in cellular senescence and cancer. However, very little is known about the structure of human telomeres. In this report we purify telomeres and analyze their termini. We show that following replication the daughter telomeres have different terminal overhangs in normal diploid telomerase-negative human fibroblasts. Electron microscopy of those telomeres that have long overhangs yields 200 +/- 75 nucleotides of single-stranded DNA. This overhang is four times greater than the amount of telomere shortening per division found in these cells. These results are consistent with models of telomere replication in which leading-strand synthesis generates a blunt end while lagging-strand synthesis produces a long G-rich 3' overhang, and suggest that variations in lagging-strand synthesis may regulate the rate of telomere shortening in normal diploid human cells. Our results do not exclude the possibility that nuclease processing events following leading strand synthesis result in short overhangs on one end.
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Affiliation(s)
- W E Wright
- Department of Cell Biology and Neuroscience, The University of Texas Southwestern Medical Center, Dallas, Texas 75235-9039 USA.
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27
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Lefebvre SD, Morrical SW. Interactions of the bacteriophage T4 gene 59 protein with single-stranded polynucleotides: binding parameters and ion effects. J Mol Biol 1997; 272:312-26. [PMID: 9325092 DOI: 10.1006/jmbi.1997.1264] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The gene 59 protein (gp59) of bacteriophage T4 is an important accessory protein of the phage-encoded replicative DNA helicase, gp41. The properties of this 26 kDa protein include selective binding to ssDNA, and specific interactions with both gp41 and gp32, the T4-encoded ssDNA- binding protein. gp59 stimulates many of the DNA-dependent activities of the gp41 enzyme by promoting its assembly onto gp32-ssDNA complexes. Direct interactions between gp59 and gp32-ssDNA complexes are essential for helicase assembly, and gp59-gp32 protein-protein interactions have been shown to play a central role. Presumably, the ssDNA-binding activity of gp59 is also important for helicase assembly; however, to date this activity has been poorly characterized. In this study, we present the first detailed biochemical investigation of the interactions of gp59 with single-stranded polynucleotides. Using etheno-DNA fluorescence enhancement and quantitative ssDNA-cellulose methods, we demonstrate the following: (1) gp59 binds to single-stranded polynucleotides with a binding site size of nine to ten nucleotide residues per monomer; (2) gp59 exhibits relative affinities towards four different ssDNA lattices used in this study according to the heirarchy: ssDNA (random sequence) > epsilonDNA (random sequence) > poly(dA) > poly(depsilonA); (3) gp59 exhibits two or more different polynucleotide binding modes distinguished by their cooperativities of binding, and modulated by salt and/or lattice effects; (4) gp59-ssDNA binding is characterized by a large salt effect on the association constant, consistent with multiple ionic contacts between protein and ssDNA phosphate residues and with the displacement of anions from the protein. The implications of our findings for the mechanism of action of gp59 in helicase-ssDNA assembly are discussed.
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Affiliation(s)
- S D Lefebvre
- Department of Biochemistry, University of Vermont College of Medicine, Burlington, VT 05405, USA
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Villemain JL, Giedroc DP. The N-terminal B-domain of T4 gene 32 protein modulates the lifetime of cooperatively bound Gp32-ss nucleic acid complexes. Biochemistry 1996; 35:14395-404. [PMID: 8916926 DOI: 10.1021/bi961482n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The N-terminal basic or B-domain (residues 1-21) of bacteriophage T4 gene 32 protein (gp32) provides a major determinant for highly cooperative binding by gp32 to single-stranded (ss) nucleic acids at equilibrium. In order to gain mechanistic insight into N-terminal domain function, the kinetics of dissociation of wild-type and previously characterized B-domain substitution mutant gp32s (R4K, R4Q, and K3A) from the model ribohomopolymer, poly(A), have been investigated under solution conditions identical to those used for equilibrium studies [Villemain, J. L., & Giedroc, D. P. (1993) Biochemistry 32, 11235-11246; Villemain, J. L., & Giedroc, D. P. (1996) J. Biol. Chem. 271, 27623-27629]. The dissociation of cooperatively bound gp32-poly(A) complexes was induced by sodium chloride concentration jumps and monitored by an increase in tryptophan fluorescence upon dissociation of the protein from poly(A) using stopped-flow techniques. The apparent dissociation rate constant, kd(app), for all mutant proteins studied was found to depend strongly on the initial fractional saturation of poly(A) just as was found previously for wild-type gp32. This permitted application of Lohman's model for the irreversible dissociation of cooperatively bound gp32-nucleic acid complexes [Lohman, T. M. (1983) Biopolymers 22, 1697-1713] from which the molecular rate constant, ke, the rate of dissociation of a protein monomer from teh end of a gp32-ss nucleic acid complex or protein cluster, could be determined. From the [NaCl]-dependence of kd(app), ke determined at 0.45 M NaCl, pH 8.1, 20 degrees C, was found to be 62 +/- 23, 78 +/- 8, 328 +/- 36, and 384 +/- 34 s-1 for wild-type, R4K, K3A, and R4Q gp32s, respectively. With the exception of R4K gp32, we find a striking correlation between the relative magnitudes of ke and Kapp, suggesting that the molecular defect in the equilibrium binding properties of the N-terminal domain mutants resides in the increased rate at which gp32 monomers dissociate from singly contiguous binding sites at the ends of clusters. The bimolecular association rate constant measured for wild-type gp32 and a weakly binding B-domain mutant, R4T gp32, to poly(dT) was found to be nearly identical, further evidence that the primary defect is in the dissociation reaction. We conclude that the N-terminal domain strongly modulates the lifetime of cooperatively bound gp32-polynucleotide complexes. The mechanistic and functional implications of these findings are discussed.
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Affiliation(s)
- J L Villemain
- Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843-2128, USA
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29
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Babitzke P, Bear DG, Yanofsky C. TRAP, the trp RNA-binding attenuation protein of Bacillus subtilis, is a toroid-shaped molecule that binds transcripts containing GAG or UAG repeats separated by two nucleotides. Proc Natl Acad Sci U S A 1995; 92:7916-20. [PMID: 7544009 PMCID: PMC41257 DOI: 10.1073/pnas.92.17.7916] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The trp RNA-binding attenuation protein of Bacillus subtilis, TRAP, regulates both transcription and translation by binding to specific transcript sequences. The optimal transcript sequences required for TRAP binding were determined by measuring complex formation between purified TRAP protein and synthetic RNAs. RNAs were tested that contained repeats of different trinucleotide sequences, with differing spacing between the repeats. A transcript containing GAG repeats separated by two-nucleotide spacers was bound most tightly. In addition, transmission electron microscopy was used to examine the structure of TRAP and the TRAP-transcript complex. TRAP was observed to be a toroid-shaped oligomer when free or when bound to either a natural or a synthetic RNA.
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Affiliation(s)
- P Babitzke
- Department of Biological Sciences, Stanford University, CA 94305, USA
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30
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Saroff HA. Energetics of protein-DNA interactions: an exact calculation for binding of ligands to a lattice of overlapping sites. Biopolymers 1995; 36:121-34. [PMID: 7492741 DOI: 10.1002/bip.360360203] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Exact equations are developed for analyzing the binding of ligands to a linear lattice of overlapping sites in which occupied-unoccupied as well as occupied-occupied interactions are included for the analysis of the binding isotherms. We demonstrate that positive cooperativity on the binding of ligands to multiple sites may derive from either occupied-unoccupied or occupied-occupied interactions. When the binding of proteins to linear polynucleotides and DNA has exhibited positive cooperativity protein-protein (occupied-occupied), interactions have heretofore been invoked as the sole energetic source in determining the cooperative effect. Models and equations developed previously for the analysis of these binding isotherms have included only the protein-protein interactions (usually characterized with the symbol omega). The exact equations of this paper are capable of analyzing binding data in a manner to evaluate the relative importance of both occupied-unoccupied and occupied-occupied interactions. Relations derived here are employed to analyze some existing data, and the resulting parameter values are compared to those developed with equations employing only the protein-protein (occupied-occupied) interactions. The resulting parameter values are qualitatively different. Values of the binding constants differ by about three orders of magnitude. When only protein-protein interactions are taken into account, the resulting free energy of interaction is negative, indicating attractive forces between bound protein molecules; when both occupied-unoccupied and occupied-occupied interactions are applied, the resulting free energies of interaction are positive, indicating destabilizing forces acting primarily on the polynucleotide lattice.
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Affiliation(s)
- H A Saroff
- Laboratory of Biochemical Pharmacology National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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31
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Shamoo Y, Friedman AM, Parsons MR, Konigsberg WH, Steitz TA. Crystal structure of a replication fork single-stranded DNA binding protein (T4 gp32) complexed to DNA. Nature 1995; 376:362-6. [PMID: 7630406 DOI: 10.1038/376362a0] [Citation(s) in RCA: 209] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The single-stranded DNA (ssDNA) binding protein gp32 from bacteriophage T4 is essential for T4 DNA replication, recombination and repair. In vivo gp32 binds ssDNA as the replication fork advances and stimulates replisome processivity and accuracy by a factor of several hundred. Gp32 binding affects nearly every major aspect of DNA metabolism. Among its important functions are: (1) configuring ssDNA templates for efficient use by the replisome including DNA polymerase; (2) melting out adventitious secondary structures; (3) protecting exposed ssDNA from nucleases; and (4) facilitating homologous recombination by binding ssDNA during strand displacement. We have determined the crystal structure of the gp32 DNA binding domain complexed to ssDNA at 2.2 A resolution. The ssDNA binding cleft comprises regions from three structural subdomains and includes a positively charged surface that runs parallel to a series of hydrophobic pockets formed by clusters of aromatic side chains. Although only weak electron density is seen for the ssDNA, it indicates that the phosphate backbone contacts an electropositive cleft of the protein, placing the bases in contact with the hydrophobic pockets. The DNA mobility implied by the weak electron density may reflect the role of gp32 as a sequence-independent ssDNA chaperone allowing the largely unstructured ssDNA to slide freely through the cleft.
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Affiliation(s)
- Y Shamoo
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA
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32
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Le Cam E, Frechon D, Barray M, Fourcade A, Delain E. Observation of binding and polymerization of Fur repressor onto operator-containing DNA with electron and atomic force microscopes. Proc Natl Acad Sci U S A 1994; 91:11816-20. [PMID: 7991541 PMCID: PMC45326 DOI: 10.1073/pnas.91.25.11816] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The Fur (ferric uptake regulation) protein is a global regulator that, in the presence of Fe2+, represses the expression of a number of iron-acquisition genes and virulence determinants such as toxins. Dark-field electron microscopy of positively stained Fur-DNA complexes in addition to atomic force microscopy allowed direct visualization of Fur interactions with the regulatory regions of aerobactin and hemolysin operons and provided complementary information about the structure of the complexes. According to the DNA used and the protein/DNA ratio, Fur binding to DNA results in partial or total covering of the fragments, indicating that the protein initiates polymerization along the DNA molecules at specific sites. Negative staining of Fur-DNA complexes revealed a well-ordered structure of the polymer suggesting a helical arrangement. Local rigidification of the DNA molecules resulting from Fur binding could be involved in the repression process.
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Affiliation(s)
- E Le Cam
- Laboratoire de Microscopie Cellulaire et Moléculaire, Centre National de la Recherche Scientifique, Villejuif, France
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33
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Stroumbakis ND, Li Z, Tolias PP. RNA- and single-stranded DNA-binding (SSB) proteins expressed during Drosophila melanogaster oogenesis: a homolog of bacterial and eukaryotic mitochondrial SSBs. Gene 1994; 143:171-7. [PMID: 8206370 DOI: 10.1016/0378-1119(94)90093-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Little is known about the identity and involvement of single-stranded (ss) DNA-binding (SSB) and RNA-binding proteins in developmental processes that occur during oogenesis in Drosophila melanogaster (Dm). Here, we describe a molecular approach designed to identify such proteins by virtue of their ssDNA-binding activity. We have constructed a directional ovarian cDNA library and conducted expression cloning screens which identified five unique cDNAs that encode proteins capable of binding ssDNA. All five represent previously unreported sequences. The remainder of this paper focuses on one of these cDNAs which encodes a Dm protein displaying significant sequence homology to Escherichia coli ssDNA-binding protein (SSB, involved in DNA replication, repair and recombination), as well as eukaryotic SSBs isolated from the mitochondria (mt) of rats, frogs, humans and yeast. The deduced amino acid (aa) sequence of this 15.6-kDa protein, which we will refer to as Dm mtSSB, displays average identities of 38.3% with eukaryotic mtSSBs and 23.4% with bacterial SSBs. Gel retardation analysis with an affinity-purified GST fusion protein confirms that Dm mtSSB specifically binds ss, but not double stranded DNA. Dm mtSSB is encoded by a nuclear gene whose expression appears to be developmentally regulated. It is expressed as a single 600-nucleotide (nt) transcript during oogenesis and embryogenesis. A larger transcript of 1500 nt is prevalent in some later stages of Dm development.
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34
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Kim YT, Richardson CC. Bacteriophage T7 gene 2.5 protein: an essential protein for DNA replication. Proc Natl Acad Sci U S A 1993; 90:10173-7. [PMID: 8234273 PMCID: PMC47736 DOI: 10.1073/pnas.90.21.10173] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The product of gene 2.5 of bacteriophage T7, a single-stranded DNA binding protein, physically interacts with the phage-encoded gene 5 protein (DNA polymerase) and gene 4 proteins (helicase and primase) and stimulates their activities. Genetic analysis of T7 phage defective in gene 2.5 shows that the gene 2.5 protein is essential for T7 DNA replication and growth. T7 phages that contain null mutants of gene 2.5 were constructed by homologous recombination. These gene 2.5 null mutants contain either a deletion of gene 2.5 (T7 delta 2.5) or an insertion into gene 2.5 and cannot grow in Escherichia coli (efficiency of plating, < 10(-8)). After infection of E. coli with T7 delta 2.5, host DNA synthesis is shut off, and phage DNA synthesis is reduced to < 1% of phage DNA synthesis in wild-type T7-infected E. coli cells as measured by incorporation of [3H]thymidine. In contrast, RNA synthesis is essentially normal in T7 delta 2.5-infected cells. The defects in growth and DNA replication are overcome by wild-type gene 2.5 protein expressed from a plasmid harboring the T7 gene 2.5.
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Affiliation(s)
- Y T Kim
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
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35
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Hansma HG, Sinsheimer RL, Groppe J, Bruice TC, Elings V, Gurley G, Bezanilla M, Mastrangelo IA, Hough PV, Hansma PK. Recent advances in atomic force microscopy of DNA. SCANNING 1993; 15:296-299. [PMID: 8269178 DOI: 10.1002/sca.4950150509] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Three advances involving DNA in atomic force microscopy (AFM) are reported here. First a HEPES-Mg buffer has been used that improves the spreading of DNA and provides good DNA coverage with as little as 200-500 picograms per sample. Second, the new "tapping" mode has been used to improve the ease and resolution of AFM-imaging of DNA in air. Finally, AFM images are presented of single-stranded phi X-174 virion DNA with the gene 32 single-stranded binding protein. A summary of the current state of the field and of the methods for preparing and imaging DNA in the AFM is also presented.
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Affiliation(s)
- H G Hansma
- Department of Physics, University of California, Santa Barbara 93106
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36
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Zijderveld DC, Stuiver MH, van der Vliet PC. The adenovirus DNA binding protein enhances intermolecular DNA renaturation but inhibits intramolecular DNA renaturation. Nucleic Acids Res 1993; 21:2591-8. [PMID: 8332457 PMCID: PMC309586 DOI: 10.1093/nar/21.11.2591] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The Adenovirus DNA binding protein (DBP) imposes a regular, rigid and extended conformation on single stranded DNA (ssDNA) and removes secondary structure. Here we show that DBP promotes renaturation of complementary single DNA strands. Enhancement of intermolecular renaturation is sequence independent, can be observed over a broad range of ionic conditions and occurs only when the DNA strands are completely covered with DBP. When one strand of DNA is covered with DBP and its complementary strand with T4 gene 32 protein, renaturation is still enhanced compared to protein-free DNA, indicating that the structures of both protein-DNA complexes are compatible for renaturation. In contrast to promoting intermolecular renaturation, DBP strongly inhibits intramolecular renaturation required for the formation of a panhandle from an ssDNA molecule with an inverted terminal repeat. We explain this by the rigidity of an ssDNA-DBP complex. These results will be discussed in view of the crystal structure of DBP that has recently been determined.
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Affiliation(s)
- D C Zijderveld
- Laboratory for Physiological Chemistry, University of Utrecht, The Netherlands
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37
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Keyes RS, Bobst AM. A comparative study of Scatchard-type and linear lattice models for the analysis of EPR competition experiments with spin-labeled nucleic acids and single-strand binding proteins. Biophys Chem 1993; 45:281-303. [PMID: 8382967 DOI: 10.1016/0301-4622(93)80009-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
An EPR competition formalism is developed which provides relative affinities of proteins for nucleic acids. Two models for analyzing protein-nucleic acid interactions, one assuming independent binding sites (Model 1) and the other considering site overlap (Model 2), are examined with respect to their validity and limitations. The models are employed to derive affinity ratio relationships which are used to calculate the relative affinities of gene 32, gene 5, and SSB proteins for various nucleic acids. It is determined that although Model 2 must be used when determining absolute binding constants, by taking the ratio of binding constants the site overlap becomes unimportant under conditions of moderate to high cooperativity and relatively small site size. This allows Model 1 to considerably simplify binding analyses. Both models are applied to the single-strand binding proteins of bacteriophage T4 gene 32, bacteriophage fd gene 5, and the Escherichia coli ssb gene, and the results are compared.
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Affiliation(s)
- R S Keyes
- Department of Chemistry, University of Cincinnati, OH 45221
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38
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Traub P, Mothes E, Shoeman R, Kühn S, Scherbarth A. Characterization of the nucleic acid-binding activities of the isolated amino-terminal head domain of the intermediate filament protein vimentin reveals its close relationship to the DNA-binding regions of some prokaryotic single-stranded DNA-binding proteins. J Mol Biol 1992; 228:41-57. [PMID: 1447793 DOI: 10.1016/0022-2836(92)90490-b] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In order to demonstrate that the nucleic acid-binding activities of vimentin are dictated by its Arg-rich N-terminal head domain, this was cut off at position Lys96 with lysine-specific endoproteinase and analysed for its capacity to associate with a variety of synthetic and naturally occurring nucleic acids. The isolated polypeptide (vim NT) showed a preference for single-stranded (ss) polynucleotides, particularly for ssDNAs of high G-content. A comparison of the sequence and predicted secondary structure of vim NT with that of two prokaryotic ssDNA-binding proteins, G5P and G32P of bacteriophages fd and T4, respectively, revealed that the nucleic acid-binding region of all three polypeptides is almost entirely in the beta-conformation and characterized by a very similar distribution of aromatic amino acid residues. A partial sequence of vim NT can be folded into the same beta-loop structure as the DNA-binding wing of G5P of bacteriophage fd and related viruses. As in the case of G5P, nitration of the Tyr residues with tetranitromethane was blocked by single-stranded nucleic acids. This and spectroscopic data indicate intercalation of the Tyr aromatic ring systems between the bases of the nucleic acids and thus the contribution of a stacking component to the binding reaction. The binding was accompanied by significant changes in the ultraviolet absorption spectra of both vim NT and single-stranded nucleic acids. Upon mixing of vim NT with nucleic acids, massive precipitation of the reactants occurred, followed by the quick rearrangement of the aggregates with the formation of specific and soluble association products. Even at very high ionic strengths, at which no electrostatic reaction should be expected, a distinct fraction of vim NT incorporated naturally occurring ssRNAs and ssDNAs into fast sedimenting complexes, suggesting co-operative interaction of the polypeptide with the nucleic acids. In electron microscopy, the complexes obtained from 28 S rRNA appeared as networks of extended nucleic acid strands densely covered with vim NT, in contrast to the compact random coils of uncomplexed RNA. The networks produced from fd DNA were heterogeneous in appearance and their nucleoprotein strands in rare cases were very similar to the rod-like structures of G5P-fd DNA complexes.
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Affiliation(s)
- P Traub
- Max-Planck-Institut für Zellbiologie, Ladenburg Federal Republic of Germany
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39
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Markiewicz P, Malone C, Chase JW, Rothman-Denes LB. Escherichia coli single-stranded DNA-binding protein is a supercoiled template-dependent transcriptional activator of N4 virion RNA polymerase. Genes Dev 1992; 6:2010-9. [PMID: 1383090 DOI: 10.1101/gad.6.10.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Coliphage N4 is a double-stranded DNA virus that requires the sequential activity of three different RNA polymerases during infection. The N4 virion RNA polymerase, which is carried in the virion and is injected with the DNA at the start of infection, is responsible for the synthesis of N4 early RNAs. In vitro, the virion RNA polymerase can transcribe double-stranded N4 DNA accurately and efficiently but only when the DNA is denatured. We have shown previously that the activity of DNA gyrase is required for in vivo early N4 transcription. We report here that Escherichia coli single-stranded DNA-binding protein (SSB) is also required for N4 early transcription. In vitro, linear or relaxed templates cannot be activated by SSB; however, supercoiled template and SSB allow the virion polymerase to recognize its promoters on duplex DNA and activate transcription. The effects of supercoiling are limited to transcript initiation and are not required for transcript elongation. The activation is specific for SSB; no other single-stranded DNA-binding proteins can substitute. Therefore, SSB is one of a small number of proteins that function to stimulate both replication and transcription. The basis for the specificity of SSB, the mechanism of transcriptional activation by SSB and template supercoiling, and their role in the N4 transcriptional program during development are discussed.
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Affiliation(s)
- P Markiewicz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637
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40
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Carty MP, Levine AS, Dixon K. HeLa cell single-stranded DNA-binding protein increases the accuracy of DNA synthesis by DNA polymerase alpha in vitro. Mutat Res 1992; 274:29-43. [PMID: 1375330 DOI: 10.1016/0921-8777(92)90041-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
To determine whether cellular replication factors can influence the fidelity of DNA replication, the effect of HeLa cell single-stranded DNA-binding protein (SSB) on the accuracy of DNA replication by HeLa cell DNA polymerase alpha has been examined. An in vitro gap-filling assay, in which the single-stranded gap contains the supF target gene, was used to measure mutagenesis. Addition of SSB to the in vitro DNA synthesis reaction increased the accuracy of DNA polymerase alpha by 2- to 8-fold. Analysis of the products of DNA synthesis indicated that SSB reduces pausing by the polymerase at specific sites in the single-stranded supF template. Sequence analysis of the types of errors resulting from synthesis in the absence or presence of SSB reveals that, while the errors are primarily base substitutions under both conditions, SSB reduces the number of errors found at 3 hotspots in the supF gene. Thus, a cellular replication factor (SSB) can influence the fidelity of a mammalian DNA polymerase in vitro, suggesting that the high accuracy of cellular DNA replication may be determined in part by the interaction between replication factors, DNA polymerase and the DNA template in the replication complex.
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Affiliation(s)
- M P Carty
- Section on Viruses and Cellular Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
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41
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Miranda EI, Garrido-Guerrero E, Garcia-Carranca A, Gariglio P. Immunoprecipitation of SV40 replicating minichromosomes complexed with bacteriophage T4 gene 32 protein. Nucleic Acids Res 1992; 20:903-7. [PMID: 1311833 PMCID: PMC312035 DOI: 10.1093/nar/20.4.903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Simian Virus 40 (SV40) DNA replication is a useful model to study eukaryotic cell DNA replication because it encodes only one replication protein and its genome has a nucleoprotein structure ('minichromosome') indistinguishable from cellular chromatin. Late after infection SV40 replicating DNA molecules represent about 5% of total viral minichromosomes. Since gene 32 protein (P32) from bacteriophage T4 interacts with single-stranded DNA and SV40 replication complexes are expected to contain single-stranded regions at the replication forks, we asked whether P32 might be used to isolate replicating SV40 minichromosomes. When nuclear extracts from SV40 infected cells were treated sequentially with P32 and anti-P32 antibodies, pulse-labeled minichromosomes were selectively immunoprecipitated. Agarose gel electrophoresis analysis confirmed that immunoprecipitated material corresponded to SV40 replicative intermediates. Protein analysis of the pelleted material revealed several proteins of viral and cellular origin. Among them, T antigen and histones were found to be complexed with at least other three proteins from cellular origin, to the replicative complexes. Additionally, anti-P32 antibodies were able to detect three cellular proteins of approximately 70, 32 and 13 kDa in western blots. These proteins could correspond to those found as part of an eukaryotic multisubunit single-stranded DNA binding protein. The use of P32 and anti-P32 antibodies thus allows the separation of replicating from mature SV40 minichromosomes and can constitute a novel method to enrich and to study replicative active chromatin.
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Affiliation(s)
- E I Miranda
- Department of Genetics and Molecular Biology, Centro de Investigacion y de Estudios Avanzados IPN, Mexico
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42
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Le Cam E, Théveny B, Mignotte B, Révet B, Delain E. Quantitative electron microscopic analysis of DNA-protein interactions. JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 1991; 18:375-86. [PMID: 1656003 DOI: 10.1002/jemt.1060180406] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Electron microscopy offers a unique potentiality to visualize individual molecules. For the last 30 years it has been used to study the structure and the interactions of various biological macromolecules. The contribution of electron microscopy is important because of its capacity to demonstrate the existence of conformational structures such as kinks, bents, loops, etc., either on naked DNA, or on DNA associated with various proteins or ligands. Increasing interest was given to such observations when it was found that they provide a direct visualization of interacting molecules involved in DNA metabolism and gene regulation. Technical advances in the preparation of the specimens, their observation in the electron microscope, and the image processing by computers have allowed the shifting from qualitative to quantitative analysis, as illustrated by a few examples from our laboratory.
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Affiliation(s)
- E Le Cam
- Laboratoire de Microscopie Cellulaire et Moléculaire, URA 147 and SDI6268 du CNRS, Institut Gustave-Roussy, Villejuif, France
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43
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The core proteins A2 and B1 exist as (A2)3B1 tetramers in 40S nuclear ribonucleoprotein particles. Mol Cell Biol 1991. [PMID: 1990289 DOI: 10.1128/mcb.11.2.864] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The six "core" proteins of HeLa cell 40S nuclear ribonucleoprotein particles (hnRNP particles) package 700-nucleotide lengths of pre-mRNA into a repeating array of regular particles. We have previously shown that the C proteins exist as anisotropic tetramers of (C1)3C2 in 40S hnRNP particles and that each particle probably contains three such tetramers. We report here that proteins A2 and B1 also exist in monoparticles as (A2)3B1 tetramers and that each monoparticle contains at least three such tetramers. Proteins A2 and B1 dissociate from isolated monoparticles as a stable tetramer upon nuclease digestion. In low-salt gradients, the tetramers sediment at 6.8S, which is consistent with a mass of 145 kDa. In 200 mM salt, the concentration which dissociates these proteins from RNA, only 4.2S dimers exist in solution. Tetramers of (A2)3B1 possess the ability to package multiples of 700 nucleotides of RNA in vitro into an array of regular, 22.5-nm 43S particles. Unlike the in vitro assembly of intact 40S hnRNP, the (A2)3B1 tetramers assemble by means of a highly cooperative process. These findings indicate that the (A2)3B1 tetramers play a major role in hnRNP assembly and they further support the contention that 40S monoparticles are regular structures composed of three copies of three different tetramers, i.e., 3[(A1)3B2, (A2)3B1, (C1)3C2].
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44
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Müller M, Wurtz M, Kellenberger E, Aebi U. Physiological, morphological, and physicochemical characterization of a novel Escherichia coli bacteriophage, phage MM. J Struct Biol 1991; 106:17-30. [PMID: 2059549 DOI: 10.1016/1047-8477(91)90059-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A double-stranded DNA containing, T even-like, Escherichia coli bacteriophage, called MM, has been isolated from the local sewage and purified by polyethylene glycol precipitation followed by banding on a cesium chloride three-step gradient. It yields a burst size of 75 particles per infected cell, and has an adsorption coefficient of 3.3 x 10(-10) cm3/min and a latent period of 45 min. Electron microscopy of phage MM reveals an isometric icosahedral head, 92 nm long and 81 nm wide, and a 112-nm-long contractile tail with six pairs of 40-nm-long fibers attached to its baseplate. Phage MM appears similar to E. coli phage T4 or Salmonella phage O1. The density of phage MM in cesium chloride is 1.515 g/ml, and its total mass is 144 MDa. Gel electrophoresis of purified MM capsids displays two major capsid proteins in approximately equimolar amounts and with apparent molecular masses of 38 and 15 kDa. Similarly, purified MM tails yield two major polypeptides with apparent molecular masses of 55 and 16 kDa, most likely representing the major tail sheath and tail tube polypeptides. Its double-stranded DNA has a G-C content of 50%, a length of 131 kilobases (kb), and a mass of 89 MDa.
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Affiliation(s)
- M Müller
- M. E. Müller-Institute for High-Resolution Electron Microscopy, Biocenter, University of Basel, Switzerland
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The core proteins A2 and B1 exist as (A2)3B1 tetramers in 40S nuclear ribonucleoprotein particles. Mol Cell Biol 1991; 11:864-71. [PMID: 1990289 PMCID: PMC359738 DOI: 10.1128/mcb.11.2.864-871.1991] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The six "core" proteins of HeLa cell 40S nuclear ribonucleoprotein particles (hnRNP particles) package 700-nucleotide lengths of pre-mRNA into a repeating array of regular particles. We have previously shown that the C proteins exist as anisotropic tetramers of (C1)3C2 in 40S hnRNP particles and that each particle probably contains three such tetramers. We report here that proteins A2 and B1 also exist in monoparticles as (A2)3B1 tetramers and that each monoparticle contains at least three such tetramers. Proteins A2 and B1 dissociate from isolated monoparticles as a stable tetramer upon nuclease digestion. In low-salt gradients, the tetramers sediment at 6.8S, which is consistent with a mass of 145 kDa. In 200 mM salt, the concentration which dissociates these proteins from RNA, only 4.2S dimers exist in solution. Tetramers of (A2)3B1 possess the ability to package multiples of 700 nucleotides of RNA in vitro into an array of regular, 22.5-nm 43S particles. Unlike the in vitro assembly of intact 40S hnRNP, the (A2)3B1 tetramers assemble by means of a highly cooperative process. These findings indicate that the (A2)3B1 tetramers play a major role in hnRNP assembly and they further support the contention that 40S monoparticles are regular structures composed of three copies of three different tetramers, i.e., 3[(A1)3B2, (A2)3B1, (C1)3C2].
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Gutiérrez C, Martín G, Sogo JM, Salas M. Mechanism of stimulation of DNA replication by bacteriophage phi 29 single-stranded DNA-binding protein p5. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52215-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Abstract
The single-stranded DNA-binding protein (SSB) of Escherichia coli is involved in all aspects of DNA metabolism: replication, repair, and recombination. In solution, the protein exists as a homotetramer of 18,843-kilodalton subunits. As it binds tightly and cooperatively to single-stranded DNA, it has become a prototypic model protein for studying protein-nucleic acid interactions. The sequences of the gene and protein are known, and the functional domains of subunit interaction, DNA binding, and protein-protein interactions have been probed by structure-function analyses of various mutations. The ssb gene has three promoters, one of which is inducible because it lies only two nucleotides from the LexA-binding site of the adjacent uvrA gene. Induction of the SOS response, however, does not lead to significant increases in SSB levels. The binding protein has several functions in DNA replication, including enhancement of helix destabilization by DNA helicases, prevention of reannealing of the single strands and protection from nuclease digestion, organization and stabilization of replication origins, primosome assembly, priming specificity, enhancement of replication fidelity, enhancement of polymerase processivity, and promotion of polymerase binding to the template. E. coli SSB is required for methyl-directed mismatch repair, induction of the SOS response, and recombinational repair. During recombination, SSB interacts with the RecBCD enzyme to find Chi sites, promotes binding of RecA protein, and promotes strand uptake.
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Affiliation(s)
- R R Meyer
- Department of Biological Sciences, University of Cincinnati, Ohio 45221
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Pakula TM, Caldentey J, Serrano M, Gutierrez C, Hermoso JM, Salas M, Bamford DH. Characterization of a DNA binding protein of bacteriophage PRD1 involved in DNA replication. Nucleic Acids Res 1990; 18:6553-7. [PMID: 2251117 PMCID: PMC332609 DOI: 10.1093/nar/18.22.6553] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Escherichia coli phage PRD1 protein P12, involved in PRD1 DNA replication in vivo, has been highly purified from E. coli cells harbouring a gene XII-containing plasmid. Protein P12 binds to single-stranded DNA as shown by gel retardation assays and nuclease protection experiments. Binding of protein P12 to single-stranded DNA increases about 14% the contour length of the DNA as revealed by electron microscopy. Binding to single-stranded DNA seems to be cooperative, and it is not sequence specific. Protein P12 also binds to double-stranded DNA although with an affinity 10 times lower than to single-stranded DNA. Using the in vitro phage phi 29 DNA replication system, it is shown that protein P12 stimulates the overall phi 29 DNA replication.
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Affiliation(s)
- T M Pakula
- Department of Genetics, University of Helsinki, Finland
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Matsumoto Y, Fishel R, Wickner RB. Circular single-stranded RNA replicon in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 1990; 87:7628-32. [PMID: 1699230 PMCID: PMC54801 DOI: 10.1073/pnas.87.19.7628] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Circular RNA replicons have been reported in plants and, in one case, in animal cells. We describe such an element in yeast. In certain yeast strains, a 20S RNA species appears on transfer of cells to acetate medium. This phenotype shows cytoplasmic (non-Mendelian) inheritance and the 20S RNA is associated with 23-kDa protein subunits as a 32S particle. We demonstrate that yeast 20S RNA is an independent replicon with no homology to host genomic, mitochondrial, or 2-microns plasmid DNA or to the L-A, L-BC, or M1 double-stranded RNA viruses of yeast. The circularity of the 20S RNA is shown by the apparent absence of 3' and 5' ends, by two-dimensional gel electrophoresis, and by electron microscopy. Replication of yeast 20S RNA proceeds through an RNA-RNA pathway, and a 10,000-fold amplification occurs on shift to acetate medium. The copy number of 20S RNA is also reduced severalfold by the SKI gene products, a host antiviral system that also lowers the copy numbers of yeast double-stranded RNA viruses. Yeast 20S RNA and the hepatitis delta virus show some similarities.
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Affiliation(s)
- Y Matsumoto
- Section on Genetics of Simple Eukaryotes, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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