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Cajili MKM, Prieto EI. Atomic Force Microscopy Characterization of Reconstituted Protein-DNA Complexes. Methods Mol Biol 2024; 2819:279-295. [PMID: 39028512 DOI: 10.1007/978-1-0716-3930-6_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Atomic force microscopy is a high-resolution imaging technique useful for observing the structures of biomolecular complexes. This approach provides a straightforward method to characterize the binding behavior of different chromatin architectural proteins and to analyze the increasingly complex structural units assembled on the DNA. The protocol describes the preparation, AFM imaging, and structural analysis of chromatin that is reconstituted in vitro using purified proteins and DNA. Here, we describe the successful application of the method on the chromatin architectural proteins of the archaeon Sulfolobus solfataricus.
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Affiliation(s)
| | - Eloise I Prieto
- National Institute of Molecular Biology and Biotechnology, University of the Philippines, Quezon City, Philippines.
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2
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K G, Verma A, Mondal P, Mandal SS. Molecular contacts in the Cren7-DNA complex: A quantitative investigation for electrostatic interaction. Biophys J 2023; 122:1701-1719. [PMID: 37016575 PMCID: PMC10183371 DOI: 10.1016/j.bpj.2023.03.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 02/15/2023] [Accepted: 03/29/2023] [Indexed: 04/06/2023] Open
Abstract
The molecular association of proteins with nucleic acids leading to the formation of macromolecular complexes is a crucial step in several biological processes. Stabilization of these complexes involves electrostatic interactions between ion pairs (salt bridges) of nucleic acid phosphates and protein side chains. The crenarchaeal DNA binding protein, Cren7 plays a key role in the regulation of chromosomal structure and gene expression in eukaryotic extremophiles. However, the molecular contacts that occur at the interface of protein-DNA complexes and their contribution to the electrostatic interaction have not been fully elucidated. This work presents a quantitative description of the mechanism of the electrostatic interaction between the protein and DNA. We have identified a few residues located at the Cren7-DNA interface that could potentially be responsible for the interaction. Structural studies using circular dichroism indicate mutation of these surface residues minimally affect their structure and stability. The binding affinity of these mutants for the DNA duplexes was examined from reverse titration, biolayer interferometry, and fluorescence anisotropy measurements with calf thymus DNA, polynucleotides, and small DNA oligonucleotides. The resulting kinetic parameters highlight a difference in electrostatic interactions potentials exhibited by residues positioned at different locations of the protein-DNA interface. Computational studies attribute this difference to their surrounding atmosphere and energetic stabilization parameters. The biophysical approach described here can be extended for other proteins that play a crucial role in DNA bending and compaction, to properly evaluate the role of specific residues on the mechanisms of DNA binding.
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Affiliation(s)
- Geethika K
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati, Andhra Pradesh, India
| | - Arunima Verma
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati, Andhra Pradesh, India
| | - Padmabati Mondal
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati, Andhra Pradesh, India.
| | - Soumit S Mandal
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati, Andhra Pradesh, India.
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3
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Essentiality of core hydrophobicity to the structure and function of archaeal chromatin protein Cren7. Int J Biol Macromol 2022; 214:381-390. [PMID: 35728637 DOI: 10.1016/j.ijbiomac.2022.06.114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 04/29/2022] [Accepted: 06/14/2022] [Indexed: 11/23/2022]
Abstract
Studies on the structure-function relationship of protein greatly help to understand not only the principles of protein folding but also the rationales of protein engineering. Crenarchaeal chromatin protein Cren7 provides an excellent research model for this issue. The small protein adopts a 'β-barrel' fold, formed by the double-stranded antiparallel β-sheet 1 tightly packing with the triple-stranded antiparallel β-sheet 2. The simple structure of Cren7 is stabilized by the hydrophobic core between the β-sheets, consisting of the side chains of V8, V10, L20, V25, F41 and F50. In the present work, mutation analyses by alanine substitution of each of the residues in the hydrophobic core were performed. Circular dichroism spectra and nuclear magnetic resonance analyses showed that mutation of F41 led to a significant misfolding of Cren7 through disruption of the β-sheets. Meanwhile, the mutant F41A showed a reduced thermostatility (Tm of 53.2 °C), as compared with the wild-type Cren7 (Tm > 80 °C). Biolayer interferometry and nick-closure assays showed the largely unchanged activities in DNA binding and supercoiling of F41A, indicating the DNA interface of Cren7 was generally retained in F41A. However, F41A was unable to mediate DNA bridging, probably due to the impairment in forming oligomers/polymers on DNA. Atomic force microscopic images of the F41A-DNA complexes also revealed that F41A nearly completely lost the ability to compact DNA into highly condensed structures. Our results not only reveal the critical role of F41 in protein folding of Cren7 but also provide new insights into the structure-function relationships of thermostable proteins.
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Small Prokaryotic DNA-Binding Proteins Protect Genome Integrity throughout the Life Cycle. Int J Mol Sci 2022; 23:ijms23074008. [PMID: 35409369 PMCID: PMC8999374 DOI: 10.3390/ijms23074008] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 03/27/2022] [Accepted: 04/01/2022] [Indexed: 12/17/2022] Open
Abstract
Genomes of all organisms are persistently threatened by endogenous and exogenous assaults. Bacterial mechanisms of genome maintenance must provide protection throughout the physiologically distinct phases of the life cycle. Spore-forming bacteria must also maintain genome integrity within the dormant endospore. The nucleoid-associated proteins (NAPs) influence nucleoid organization and may alter DNA topology to protect DNA or to alter gene expression patterns. NAPs are characteristically multifunctional; nevertheless, Dps, HU and CbpA are most strongly associated with DNA protection. Archaea display great variety in genome organization and many inhabit extreme environments. As of yet, only MC1, an archaeal NAP, has been shown to protect DNA against thermal denaturation and radiolysis. ssDNA are intermediates in vital cellular processes, such as DNA replication and recombination. Single-stranded binding proteins (SSBs) prevent the formation of secondary structures but also protect the hypersensitive ssDNA against chemical and nuclease degradation. Ionizing radiation upregulates SSBs in the extremophile Deinococcus radiodurans.
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Cajili MKM, Prieto EI. Interplay between Alba and Cren7 Regulates Chromatin Compaction in Sulfolobus solfataricus. Biomolecules 2022; 12:biom12040481. [PMID: 35454068 PMCID: PMC9030869 DOI: 10.3390/biom12040481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/03/2022] [Accepted: 03/15/2022] [Indexed: 01/06/2023] Open
Abstract
Chromatin compaction and regulation are essential processes for the normal function of all organisms, yet knowledge on how archaeal chromosomes are packed into higher-order structures inside the cell remains elusive. In this study, we investigated the role of archaeal architectural proteins Alba and Cren7 in chromatin folding and dynamics. Atomic force microscopy revealed that Sulfolobus solfataricus chromatin is composed of 28 nm fibers and 60 nm globular structures. In vitro reconstitution showed that Alba can mediate the formation of folded DNA structures in a concentration-dependent manner. Notably, it was demonstrated that Alba on its own can form higher-order structures with DNA. Meanwhile, Cren7 was observed to affect the formation of Alba-mediated higher-order chromatin structures. Overall, the results suggest an interplay between Alba and Cren7 in regulating chromatin compaction in archaea.
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Ding N, Chen Y, Chu Y, Zhong C, Huang L, Zhang Z. Lysine Methylation Modulates the Interaction of Archaeal Chromatin Protein Cren7 With DNA. Front Microbiol 2022; 13:837737. [PMID: 35308404 PMCID: PMC8927968 DOI: 10.3389/fmicb.2022.837737] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/28/2022] [Indexed: 12/15/2022] Open
Abstract
Cren7 and Sis7d, two chromatin proteins from Sulfolobus islandicus, undergo extensive methylations at multiple lysine residues to various extents. Whether this highly conserved protein serves an epigenetic role in the regulation of the structure and function of the chromosome remains unclear. In the present study, we show that methylation significantly affects Cren7, but not Sis7d, in the ability to bind DNA and to constrain negative DNA supercoils. Strikingly, methylated Cren7 was significantly less efficient in forming oligomers or mediating intermolecular DNA bridging. Single-site substitution mutation with glutamine reveals that methylation of the four lysine residues (K24, K31, K42, and K48) of Cren7 at the protein-DNA interface, which are variably conserved among Cren7 homologues from different branches of the Crenarchaeota, influenced Cren7-DNA interactions in different manners. We suggest that dynamic methylation of Cren7 may represent a potential epigenetic mechanism involved in the chromosomal regulation in crenarchaea.
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Affiliation(s)
- Niannian Ding
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yuanyuan Chen
- The Research Platform for Protein Sciences, Institute of Biophysics, Chinese Academy of Sciences (CAS), Beijing, China
| | - Yindi Chu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, China
| | - Cheng Zhong
- State Key Laboratory of Food Nutrition and Safety, Tianjin University of Science & Technology, Tianjin, China
| | - Li Huang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
- *Correspondence: Zhenfeng Zhang,
| | - Zhenfeng Zhang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
- Li Huang,
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K G, Thomas AR, T SV, Mandal SS. Structural and thermodynamic insights into the Cren7 mediated DNA organization in Crenarchaeota. Phys Chem Chem Phys 2022; 24:19401-19413. [DOI: 10.1039/d2cp02190k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Archaea have histone homologues and chromatin proteins to organize their DNA into a compact form and allow them to survive in extreme climatic conditions. Cren7 is one such chromatin protein...
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Lewis AM, Recalde A, Bräsen C, Counts JA, Nussbaum P, Bost J, Schocke L, Shen L, Willard DJ, Quax TEF, Peeters E, Siebers B, Albers SV, Kelly RM. The biology of thermoacidophilic archaea from the order Sulfolobales. FEMS Microbiol Rev 2021; 45:fuaa063. [PMID: 33476388 PMCID: PMC8557808 DOI: 10.1093/femsre/fuaa063] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 11/26/2020] [Indexed: 12/13/2022] Open
Abstract
Thermoacidophilic archaea belonging to the order Sulfolobales thrive in extreme biotopes, such as sulfuric hot springs and ore deposits. These microorganisms have been model systems for understanding life in extreme environments, as well as for probing the evolution of both molecular genetic processes and central metabolic pathways. Thermoacidophiles, such as the Sulfolobales, use typical microbial responses to persist in hot acid (e.g. motility, stress response, biofilm formation), albeit with some unusual twists. They also exhibit unique physiological features, including iron and sulfur chemolithoautotrophy, that differentiate them from much of the microbial world. Although first discovered >50 years ago, it was not until recently that genome sequence data and facile genetic tools have been developed for species in the Sulfolobales. These advances have not only opened up ways to further probe novel features of these microbes but also paved the way for their potential biotechnological applications. Discussed here are the nuances of the thermoacidophilic lifestyle of the Sulfolobales, including their evolutionary placement, cell biology, survival strategies, genetic tools, metabolic processes and physiological attributes together with how these characteristics make thermoacidophiles ideal platforms for specialized industrial processes.
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Affiliation(s)
- April M Lewis
- Department of Chemical and Biomolecular Engineering, North Carolina State University. Raleigh, NC 27695, USA
| | - Alejandra Recalde
- Institute for Biology, Molecular Biology of Archaea, University of Freiburg, 79104 Freiburg, Germany
| | - Christopher Bräsen
- Department of Molecular Enzyme Technology and Biochemistry, Environmental Microbiology and Biotechnology, and Centre for Water and Environmental Research, University of Duisburg-Essen, 45117 Essen, Germany
| | - James A Counts
- Department of Chemical and Biomolecular Engineering, North Carolina State University. Raleigh, NC 27695, USA
| | - Phillip Nussbaum
- Institute for Biology, Molecular Biology of Archaea, University of Freiburg, 79104 Freiburg, Germany
| | - Jan Bost
- Institute for Biology, Molecular Biology of Archaea, University of Freiburg, 79104 Freiburg, Germany
| | - Larissa Schocke
- Department of Molecular Enzyme Technology and Biochemistry, Environmental Microbiology and Biotechnology, and Centre for Water and Environmental Research, University of Duisburg-Essen, 45117 Essen, Germany
| | - Lu Shen
- Department of Molecular Enzyme Technology and Biochemistry, Environmental Microbiology and Biotechnology, and Centre for Water and Environmental Research, University of Duisburg-Essen, 45117 Essen, Germany
| | - Daniel J Willard
- Department of Chemical and Biomolecular Engineering, North Carolina State University. Raleigh, NC 27695, USA
| | - Tessa E F Quax
- Archaeal Virus–Host Interactions, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Eveline Peeters
- Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Bettina Siebers
- Department of Molecular Enzyme Technology and Biochemistry, Environmental Microbiology and Biotechnology, and Centre for Water and Environmental Research, University of Duisburg-Essen, 45117 Essen, Germany
| | - Sonja-Verena Albers
- Institute for Biology, Molecular Biology of Archaea, University of Freiburg, 79104 Freiburg, Germany
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University. Raleigh, NC 27695, USA
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Laursen SP, Bowerman S, Luger K. Archaea: The Final Frontier of Chromatin. J Mol Biol 2020; 433:166791. [PMID: 33383035 PMCID: PMC7987875 DOI: 10.1016/j.jmb.2020.166791] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/19/2020] [Accepted: 12/22/2020] [Indexed: 12/26/2022]
Abstract
The three domains of life employ various strategies to organize their genomes. Archaea utilize features similar to those found in both eukaryotic and bacterial chromatin to organize their DNA. In this review, we discuss the current state of research regarding the structure-function relationships of several archaeal chromatin proteins (histones, Alba, Cren7, and Sul7d). We address individual structures as well as inferred models for higher-order chromatin formation. Each protein introduces a unique phenotype to chromatin organization, and these structures are put into the context of in vivo and in vitro data. We close by discussing the present gaps in knowledge that are preventing further studies of the organization of archaeal chromatin, on both the organismal and domain level.
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Affiliation(s)
- Shawn P Laursen
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, CO 80303, United States
| | - Samuel Bowerman
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309, United States
| | - Karolin Luger
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309, United States; Howard Hughes Medical Institute, Chevy Chase, MD 20815, United States.
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Zhang Z, Zhan Z, Wang B, Chen Y, Chen X, Wan C, Fu Y, Huang L. Archaeal Chromatin Proteins Cren7 and Sul7d Compact DNA by Bending and Bridging. mBio 2020; 11:e00804-20. [PMID: 32518188 PMCID: PMC7373190 DOI: 10.1128/mbio.00804-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 05/06/2020] [Indexed: 11/20/2022] Open
Abstract
Archaeal chromatin proteins Cren7 and Sul7d from Sulfolobus are DNA benders. To better understand their architectural roles in chromosomal DNA organization, we analyzed DNA compaction by Cren7 and Sis7d, a Sul7d family member, from Sulfolobus islandicus at the single-molecule (SM) level by total single-molecule internal reflection fluorescence microscopy (SM-TIRFM) and atomic force microscopy (AFM). We show that both Cren7 and Sis7d were able to compact singly tethered λ DNA into a highly condensed structure in a three-step process and that Cren7 was over an order of magnitude more efficient than Sis7d in DNA compaction. The two proteins were similar in DNA bending kinetics but different in DNA condensation patterns. At saturating concentrations, Sis7d formed randomly distributed clusters whereas Cren7 generated a single and highly condensed core on plasmid DNA. This observation is consistent with the greater ability of Cren7 than of Sis7d to bridge DNA. Our results offer significant insights into the mechanism and kinetics of chromosomal DNA organization in Crenarchaea.IMPORTANCE A long-standing question is how chromosomal DNA is packaged in Crenarchaeota, a major group of archaea, which synthesize large amounts of unique small DNA-binding proteins but in general contain no archaeal histones. In the present work, we tested our hypothesis that the two well-studied crenarchaeal chromatin proteins Cren7 and Sul7d compact DNA by both DNA bending and bridging. We show that the two proteins are capable of compacting DNA, albeit with different efficiencies and in different manners, at the single molecule level. We demonstrate for the first time that the two proteins, which have long been regarded as DNA binders and benders, are able to mediate DNA bridging, and this previously unknown property of the proteins allows DNA to be packaged into highly condensed structures. Therefore, our results provide significant insights into the mechanism and kinetics of chromosomal DNA organization in Crenarchaeota.
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Affiliation(s)
- Zhenfeng Zhang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Zhengyan Zhan
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Bing Wang
- Hubei Key Lab of Genetic Regulation & Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, China
| | - Yuanyuan Chen
- National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xiuqiang Chen
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Cuihong Wan
- Hubei Key Lab of Genetic Regulation & Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, China
| | - Yu Fu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Li Huang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- College of Life Science, University of Chinese Academy of Sciences, Beijing, China
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