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Bell SD. Form and function of archaeal genomes. Biochem Soc Trans 2022; 50:1931-1939. [PMID: 36511238 PMCID: PMC9764264 DOI: 10.1042/bst20221396] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 11/30/2022] [Accepted: 12/01/2022] [Indexed: 07/30/2023]
Abstract
A key maxim in modernist architecture is that 'form follows function'. While modernist buildings are hopefully the product of intelligent design, the architectures of chromosomes have been sculpted by the forces of evolution over many thousands of generations. In the following, I will describe recent advances in our understanding of chromosome architecture in the archaeal domain of life. Although much remains to be learned about the mechanistic details of archaeal chromosome organization, some general principles have emerged. At the 10-100 kb level, archaeal chromosomes have a conserved local organization reminiscent of bacterial genomes. In contrast, lineage-specific innovations appear to have imposed distinct large-scale architectural features. The ultimate functions of genomes are to store and to express genetic information. Gene expression profiles have been shown to influence chromosome architecture, thus their form follows function. However, local changes to chromosome conformation can also influence gene expression and therefore, in these instances, function follows form.
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Affiliation(s)
- Stephen D. Bell
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, U.S.A
- Biology Department, Indiana University, Bloomington, IN 47405, U.S.A
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2
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A widespread group of large plasmids in methanotrophic Methanoperedens archaea. Nat Commun 2022; 13:7085. [PMID: 36400771 PMCID: PMC9674854 DOI: 10.1038/s41467-022-34588-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 10/31/2022] [Indexed: 11/19/2022] Open
Abstract
Anaerobic methanotrophic (ANME) archaea obtain energy from the breakdown of methane, yet their extrachromosomal genetic elements are little understood. Here we describe large plasmids associated with ANME archaea of the Methanoperedens genus in enrichment cultures and other natural anoxic environments. By manual curation we show that two of the plasmids are large (155,605 bp and 191,912 bp), circular, and may replicate bidirectionally. The plasmids occur in the same copy number as the main chromosome, and plasmid genes are actively transcribed. One of the plasmids encodes three tRNAs, ribosomal protein uL16 and elongation factor eEF2; these genes appear to be missing in the host Methanoperedens genome, suggesting an obligate interdependence between plasmid and host. Our work opens the way for the development of genetic vectors to shed light on the physiology and biochemistry of Methanoperedens, and potentially genetically edit them to enhance growth and accelerate methane oxidation rates.
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3
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Davidson IF, Peters JM. Genome folding through loop extrusion by SMC complexes. Nat Rev Mol Cell Biol 2021; 22:445-464. [PMID: 33767413 DOI: 10.1038/s41580-021-00349-7] [Citation(s) in RCA: 206] [Impact Index Per Article: 68.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/03/2021] [Indexed: 02/02/2023]
Abstract
Genomic DNA is folded into loops and topologically associating domains (TADs), which serve important structural and regulatory roles. It has been proposed that these genomic structures are formed by a loop extrusion process, which is mediated by structural maintenance of chromosomes (SMC) protein complexes. Recent single-molecule studies have shown that the SMC complexes condensin and cohesin are indeed able to extrude DNA into loops. In this Review, we discuss how the loop extrusion hypothesis can explain key features of genome architecture; cellular functions of loop extrusion, such as separation of replicated DNA molecules, facilitation of enhancer-promoter interactions and immunoglobulin gene recombination; and what is known about the mechanism of loop extrusion and its regulation, for example, by chromatin boundaries that depend on the DNA binding protein CTCF. We also discuss how the loop extrusion hypothesis has led to a paradigm shift in our understanding of both genome architecture and the functions of SMC complexes.
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Affiliation(s)
- Iain F Davidson
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Vienna, Austria.
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4
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Zink IA, Fouqueau T, Tarrason Risa G, Werner F, Baum B, Bläsi U, Schleper C. Comparative CRISPR type III-based knockdown of essential genes in hyperthermophilic Sulfolobales and the evasion of lethal gene silencing. RNA Biol 2021; 18:421-434. [PMID: 32957821 PMCID: PMC7951960 DOI: 10.1080/15476286.2020.1813411] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 07/22/2020] [Accepted: 08/16/2020] [Indexed: 02/07/2023] Open
Abstract
CRISPR type III systems, which are abundantly found in archaea, recognize and degrade RNA in their specific response to invading nucleic acids. Therefore, these systems can be harnessed for gene knockdown technologies even in hyperthermophilic archaea to study essential genes. We show here the broader usability of this posttranscriptional silencing technology by expanding the application to further essential genes and systematically analysing and comparing silencing thresholds and escape mutants. Synthetic guide RNAs expressed from miniCRISPR cassettes were used to silence genes involved in cell division (cdvA), transcription (rpo8), and RNA metabolism (smAP2) of the two crenarchaeal model organisms Saccharolobus solfataricus and Sulfolobus acidocaldarius. Results were systematically analysed together with those obtained from earlier experiments of cell wall biogenesis (slaB) and translation (aif5A). Comparison of over 100 individual transformants revealed gene-specific silencing maxima ranging between 40 and 75%, which induced specific knockdown phenotypes leading to growth retardation. Exceedance of this threshold by strong miniCRISPR constructs was not tolerated and led to specific mutation of the silencing miniCRISPR array and phenotypical reversion of cultures. In two thirds of sequenced reverted cultures, the targeting spacers were found to be precisely excised from the miniCRISPR array, indicating a still hypothetical, but highly active recombination system acting on the dynamics of CRISPR spacer arrays. Our results indicate that CRISPR type III - based silencing is a broadly applicable tool to study in vivo functions of essential genes in Sulfolobales which underlies a specific mechanism to avoid malignant silencing overdose.
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Affiliation(s)
- Isabelle Anna Zink
- Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
| | - Thomas Fouqueau
- RNAP Lab, Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK
| | - Gabriel Tarrason Risa
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Finn Werner
- RNAP Lab, Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK
| | - Buzz Baum
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Udo Bläsi
- Max Perutz Laboratories, University of Vienna, Vienna, Austria
| | - Christa Schleper
- Department of Functional and Evolutionary Ecology, University of Vienna, Vienna, Austria
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5
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Abstract
Over the past decade, advances in methodologies for the determination of chromosome conformation have provided remarkable insight into the local and higher-order organization of bacterial and eukaryotic chromosomes. Locally folded domains are found in both bacterial and eukaryotic genomes, although they vary in size. Importantly, genomes of metazoans also possess higher-order organization into A- and B-type compartments, regions of transcriptionally active and inactive chromatin, respectively. Until recently, nothing was known about the organization of genomes of organisms in the third domain of life - the archaea. However, despite archaea possessing simple circular genomes that are morphologically reminiscent of those seen in many bacteria, a recent study of archaea of the genus Sulfolobus has revealed that it organizes its genome into large-scale domains. These domains further interact to form defined A- and B-type compartments. The interplay of transcription and localization of a novel structural maintenance of chromosomes (SMC) superfamily protein, termed coalescin, defines compartment identity. In this Review, we discuss the mechanistic and evolutionary implications of these findings.
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Affiliation(s)
- Naomichi Takemata
- Biology Department, Indiana University, Bloomington, USA.,Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, USA
| | - Stephen D Bell
- Biology Department, Indiana University, Bloomington, USA .,Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, USA
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6
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Zink IA, Pfeifer K, Wimmer E, Sleytr UB, Schuster B, Schleper C. CRISPR-mediated gene silencing reveals involvement of the archaeal S-layer in cell division and virus infection. Nat Commun 2019; 10:4797. [PMID: 31641111 PMCID: PMC6805947 DOI: 10.1038/s41467-019-12745-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 09/18/2019] [Indexed: 12/27/2022] Open
Abstract
The S-layer is a proteinaceous surface lattice found in the cell envelope of bacteria and archaea. In most archaea, a glycosylated S-layer constitutes the sole cell wall and there is evidence that it contributes to cell shape maintenance and stress resilience. Here we use a gene-knockdown technology based on an endogenous CRISPR type III complex to gradually silence slaB, which encodes the S-layer membrane anchor in the hyperthermophilic archaeon Sulfolobus solfataricus. Silenced cells exhibit a reduced or peeled-off S-layer lattice, cell shape alterations and decreased surface glycosylation. These cells barely propagate but increase in diameter and DNA content, indicating impaired cell division; their phenotypes can be rescued through genetic complementation. Furthermore, S-layer depleted cells are less susceptible to infection with the virus SSV1. Our study highlights the usefulness of the CRISPR type III system for gene silencing in archaea, and supports that an intact S-layer is important for cell division and virus susceptibility. The S-layer is a proteinaceous envelope often found in bacterial and archaeal cells. Here, the authors use CRISPR-based technology to silence slaB, encoding the S-layer membrane anchor, to show that an intact S-layer is important for cell division and virus susceptibility in the archaeon Sulfolobus solfataricus.
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Affiliation(s)
- Isabelle Anna Zink
- Archaea Biology and Ecogenomics Division, Althanstraße 14, University of Vienna, A-1090, Vienna, Austria
| | - Kevin Pfeifer
- Archaea Biology and Ecogenomics Division, Althanstraße 14, University of Vienna, A-1090, Vienna, Austria.,Institute for Synthetic Bioarchitectures, Muthgasse 11/II, University of Natural Resources and Life Sciences, A-1190, Vienna, Austria
| | - Erika Wimmer
- Archaea Biology and Ecogenomics Division, Althanstraße 14, University of Vienna, A-1090, Vienna, Austria
| | - Uwe B Sleytr
- Institute of Biophysics, Muthgasse 11/II, University of Natural Resources and Life Sciences, A-1190, Vienna, Austria
| | - Bernhard Schuster
- Institute for Synthetic Bioarchitectures, Muthgasse 11/II, University of Natural Resources and Life Sciences, A-1190, Vienna, Austria
| | - Christa Schleper
- Archaea Biology and Ecogenomics Division, Althanstraße 14, University of Vienna, A-1090, Vienna, Austria.
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7
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Barillà D. Driving Apart and Segregating Genomes in Archaea. Trends Microbiol 2016; 24:957-967. [PMID: 27450111 PMCID: PMC5120986 DOI: 10.1016/j.tim.2016.07.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 06/16/2016] [Accepted: 07/01/2016] [Indexed: 11/01/2022]
Abstract
Genome segregation is a fundamental biological process in organisms from all domains of life. How this stage of the cell cycle unfolds in Eukarya has been clearly defined and considerable progress has been made to unravel chromosome partition in Bacteria. The picture is still elusive in Archaea. The lineages of this domain exhibit different cell-cycle lifestyles and wide-ranging chromosome copy numbers, fluctuating from 1 up to 55. This plurality of patterns suggests that a variety of mechanisms might underpin disentangling and delivery of DNA molecules to daughter cells. Here I describe recent developments in archaeal genome maintenance, including investigations of novel genome segregation machines that point to unforeseen bacterial and eukaryotic connections.
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Affiliation(s)
- Daniela Barillà
- Department of Biology, University of York, York YO10 5DD, UK.
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8
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Novikova O, Jayachandran P, Kelley DS, Morton Z, Merwin S, Topilina NI, Belfort M. Intein Clustering Suggests Functional Importance in Different Domains of Life. Mol Biol Evol 2015; 33:783-99. [PMID: 26609079 PMCID: PMC4760082 DOI: 10.1093/molbev/msv271] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Inteins, also called protein introns, are self-splicing mobile elements found in all domains of life. A bioinformatic survey of genomic data highlights a biased distribution of inteins among functional categories of proteins in both bacteria and archaea, with a strong preference for a single network of functions containing replisome proteins. Many nonorthologous, functionally equivalent replicative proteins in bacteria and archaea carry inteins, suggesting a selective retention of inteins in proteins of particular functions across domains of life. Inteins cluster not only in proteins with related roles but also in specific functional units of those proteins, like ATPase domains. This peculiar bias does not fully fit the models describing inteins exclusively as parasitic elements. In such models, evolutionary dynamics of inteins is viewed primarily through their mobility with the intein homing endonuclease (HEN) as the major factor of intein acquisition and loss. Although the HEN is essential for intein invasion and spread in populations, HEN dynamics does not explain the observed biased distribution of inteins among proteins in specific functional categories. We propose that the protein splicing domain of the intein can act as an environmental sensor that adapts to a particular niche and could increase the chance of the intein becoming fixed in a population. We argue that selective retention of some inteins might be beneficial under certain environmental stresses, to act as panic buttons that reversibly inhibit specific networks, consistent with the observed intein distribution.
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Affiliation(s)
- Olga Novikova
- Department of Biological Sciences and RNA Institute, University at Albany
| | | | - Danielle S Kelley
- Department of Biomedical Sciences, School of Public Health, University at Albany
| | - Zachary Morton
- Department of Biological Sciences and RNA Institute, University at Albany
| | | | - Natalya I Topilina
- Department of Biological Sciences and RNA Institute, University at Albany
| | - Marlene Belfort
- Department of Biological Sciences and RNA Institute, University at Albany Department of Biomedical Sciences, School of Public Health, University at Albany
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9
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10
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Nolivos S, Sherratt D. The bacterial chromosome: architecture and action of bacterial SMC and SMC-like complexes. FEMS Microbiol Rev 2013; 38:380-92. [PMID: 24118085 PMCID: PMC4255302 DOI: 10.1111/1574-6976.12045] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 08/09/2013] [Accepted: 08/26/2013] [Indexed: 12/27/2022] Open
Abstract
Structural Maintenance of Chromosomes (SMC) protein complexes are found in all three domains of life. They are characterized by a distinctive and conserved architecture in which a globular ATPase ‘head’ domain is formed by the N- and C-terminal regions of the SMC protein coming together, with a c. 50-nm-long antiparallel coiled-coil separating the head from a dimerization ‘hinge’. Dimerization gives both V- and O-shaped SMC dimers. The distinctive architecture points to a conserved biochemical mechanism of action. However, the details of this mechanism are incomplete, and the precise ways in which this mechanism leads to the biological functions of these complexes in chromosome organization and processing remain unclear. In this review, we introduce the properties of bacterial SMC complexes, compare them with eukaryotic complexes and discuss how their likely biochemical action relates to their roles in chromosome organization and segregation.
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Affiliation(s)
- Sophie Nolivos
- Department of Biochemistry, University of Oxford, Oxford, UK
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11
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Abstract
Growth and proliferation of all cell types require intricate regulation and coordination of chromosome replication, genome segregation, cell division and the systems that determine cell shape. Recent findings have provided insight into the cell cycle of archaea, including the multiple-origin mode of DNA replication, the initial characterization of a genome segregation machinery and the discovery of a novel cell division system. The first archaeal cytoskeletal protein, crenactin, was also recently described and shown to function in cell shape determination. Here, we outline the current understanding of the archaeal cell cycle and cytoskeleton, with an emphasis on species in the genus Sulfolobus, and consider the major outstanding questions in the field.
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Affiliation(s)
- Ann-Christin Lindås
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, SE-106 91, Stockholm, Sweden
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12
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Chromosome segregation in Archaea mediated by a hybrid DNA partition machine. Proc Natl Acad Sci U S A 2012; 109:3754-9. [PMID: 22355141 DOI: 10.1073/pnas.1113384109] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Eukarya and, more recently, some bacteria have been shown to rely on a cytoskeleton-based apparatus to drive chromosome segregation. In contrast, the factors and mechanisms underpinning this fundamental process are underexplored in archaea, the third domain of life. Here we establish that the archaeon Sulfolobus solfataricus harbors a hybrid segrosome consisting of two interacting proteins, SegA and SegB, that play a key role in genome segregation in this organism. SegA is an ortholog of bacterial, Walker-type ParA proteins, whereas SegB is an archaea-specific factor lacking sequence identity to either eukaryotic or bacterial proteins, but sharing homology with a cluster of uncharacterized factors conserved in both crenarchaea and euryarchaea, the two major archaeal sub-phyla. We show that SegA is an ATPase that polymerizes in vitro and that SegB is a site-specific DNA-binding protein contacting palindromic sequences located upstream of the segAB cassette. SegB interacts with SegA in the presence of nucleotides and dramatically affects its polymerization dynamics. Our data demonstrate that SegB strongly stimulates SegA polymerization, possibly by promoting SegA nucleation and accelerating polymer growth. Increased expression levels of segAB resulted in severe growth and chromosome segregation defects, including formation of anucleate cells, compact nucleoids confined to one half of the cell compartment and fragmented nucleoids. The overall picture emerging from our findings indicates that the SegAB complex fulfills a crucial function in chromosome segregation and is the prototype of a DNA partition machine widespread across archaea.
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13
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Shin HC, Lim JH, Woo JS, Oh BH. Focal localization of MukBEF condensin on the chromosome requires the flexible linker region of MukF. FEBS J 2009; 276:5101-10. [PMID: 19674109 DOI: 10.1111/j.1742-4658.2009.07206.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Condensin complexes are the key mediators of chromosome condensation. The MukB-MukE-MukF complex is a bacterial condensin, in which the MukB subunit forms a V-shaped dimeric structure with two ATPase head domains. MukE and MukF together form a tight complex, which binds to the MukB head via the C-terminal winged-helix domain (C-WHD) of MukF. One of the two bound C-WHDs of MukF is forced to detach from two ATP-bound, engaged MukB heads, and this detachment reaction depends on the MukF flexible linker preceding the C-WHD. Whereas MukB is known to focally localize at particular positions in cells by an unknown mechanism, mukE- or mukF-null mutation causes MukB to become dispersed in cells. Here, we report that mutations in MukF causing a defect in the detachment reaction interfere with the focal localization of MukB, and that the dispersed distribution of MukB in cells correlates directly with defects in cell growth and division. The data strongly suggest that the MukB-MukE-MukF condensin forms huge clusters through the ATP-dependent detachment reaction, and this cluster formation is critical for chromosome condensation by this machinery. We also show that the MukF flexible linker is involved in the dimerization and ATPase activity of the MukB head.
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Affiliation(s)
- Ho-Chul Shin
- Center for Biomolecular Recognition and Division of Molecular and Life Science, Pohang University of Science and Technology, Kyungbuk, Korea
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14
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AglC and AglK are involved in biosynthesis and attachment of diacetylated glucuronic acid to the N-glycan in Methanococcus voltae. J Bacteriol 2008; 191:187-95. [PMID: 18978056 DOI: 10.1128/jb.00885-08] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent advances in the field of prokaryotic N-glycosylation have established a foundation for the pathways and proteins involved in this important posttranslational protein modification process. To continue the study of the Methanococcus voltae N-glycosylation pathway, characteristics of known eukaryotic, bacterial, and archaeal proteins involved in the N-glycosylation process were examined and used to select candidate M. voltae genes for investigation as potential glycosyl transferase and flippase components. The targeted genes were knocked out via linear gene replacement, and the resulting effects on N-glycan assembly were identified through flagellin and surface (S) layer protein glycosylation defects. This study reports the finding that deletion of two putative M. voltae glycosyl transferase genes, designated aglC (for archaeal glycosylation) and aglK, interfered with proper N-glycosylation. This resulted in flagellin and S-layer proteins with significantly reduced apparent molecular masses, loss of flagellar assembly, and absence of glycan attachment. Given previous knowledge of both the N-glycosylation pathway in M. voltae and the general characteristics of N-glycosylation components, it appears that AglC and AglK are involved in the biosynthesis or transfer of diacetylated glucuronic acid within the glycan structure. In addition, a knockout of the putative flippase candidate gene (Mv891) had no effect on N-glycosylation but did result in the production of giant cells with diameters three to four times that of wild-type cells.
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15
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Rother M, Metcalf WW. Genetic technologies for Archaea. Curr Opin Microbiol 2005; 8:745-51. [PMID: 16257573 DOI: 10.1016/j.mib.2005.10.010] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 10/12/2005] [Indexed: 11/25/2022]
Abstract
Members of the third domain of life, the Archaea, possess structural, physiological, biochemical and genetic features distinct from Bacteria and Eukarya and, therefore, have drawn considerable scientific interest. Physiological, biochemical and molecular analyses have revealed many novel biological processes in these important prokaryotes. However, assessment of the function of genes in vivo through genetic analysis has lagged behind because suitable systems for the creation of mutants in most Archaea were established only in the past decade. Among the Archaea, sufficiently sophisticated genetic systems now exist for some thermophilic sulfur-metabolizing Archaea, halophilic Archaea and methanogenic Archaea. Recently, there have been developments in genetic analysis of thermophilic and methanogenic Archaea and in the use of genetics to study the physiology, metabolism and regulatory mechanisms that direct gene expression in response to changes of environmental conditions in these important microorganisms.
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Affiliation(s)
- Michael Rother
- Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Marie-Curie-Strasse 9, D-60439 Frankfurt (Main), Germany
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16
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Lundgren M, Bernander R. Archaeal cell cycle progress. Curr Opin Microbiol 2005; 8:662-8. [PMID: 16249118 DOI: 10.1016/j.mib.2005.10.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Accepted: 10/11/2005] [Indexed: 11/19/2022]
Abstract
The discovery of multiple chromosome replication origins in Sulfolobus species has added yet another eukaryotic trait to the archaea, and brought new levels of complexity to the cell cycle in terms of initiation of chromosome replication, replication termination and chromosome decatenation. Conserved repeated DNA elements--origin recognition boxes--have been identified in the origins of replication, and shown to bind the Orc1/Cdc6 proteins involved in cell cycle control. The origin recognition boxes aid in the identification and characterization of new origins, and their conservation suggests that most archaea have a similar replication initiation mechanism. Cell-cycle-dependent variation in Orc1/Cdc6 levels has been demonstrated, reminiscent of variations in cyclin levels during the eukaryotic cell cycle. Information about archaeal chromosome segregation is also accumulating, including the identification of a protein that binds to short regularly spaced repeats that might constitute centromere-like elements. In addition, studies of cell-cycle-specific gene expression have potential to reveal, in the near future, missing components in crenarchaeal chromosome replication, genome segregation and cell division. Together with an increased number of physiological and cytological investigations of the overall organization of the cell cycle, rapid progress of the archaeal cell cycle field is evident, and archaea, in particular Sulfolobus species, are emerging as simple and powerful models for the eukaryotic cell cycle.
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Affiliation(s)
- Magnus Lundgren
- Department of Molecular Evolution, Evolutionary Biology Center, Uppsala University, Norbyvägen 18C, SE-752 36 Uppsala, Sweden
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17
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Strunnikov AV. SMC complexes in bacterial chromosome condensation and segregation. Plasmid 2005; 55:135-44. [PMID: 16229890 PMCID: PMC2670095 DOI: 10.1016/j.plasmid.2005.08.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Revised: 08/19/2005] [Accepted: 08/19/2005] [Indexed: 11/26/2022]
Abstract
Bacterial chromosomes segregate via a partition apparatus that employs a score of specialized proteins. The SMC complexes play a crucial role in the chromosome partitioning process by organizing bacterial chromosomes through their ATP-dependent chromatin-compacting activity. Recent progress in the composition of these complexes and elucidation of their structural and enzymatic properties has advanced our comprehension of chromosome condensation and segregation mechanics in bacteria.
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