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Jaspan VN, Taye ME, Carle CM, Chung JJ, Chalker DL. Boundaries of eliminated heterochromatin of Tetrahymena are positioned by the DNA-binding protein Ltl1. Nucleic Acids Res 2019; 47:7348-7362. [PMID: 31194876 PMCID: PMC6698652 DOI: 10.1093/nar/gkz504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 05/16/2019] [Accepted: 06/10/2019] [Indexed: 12/19/2022] Open
Abstract
During differentiation of the Tetrahymena thermophila somatic nucleus, its germline-derived DNA undergoes extensive reorganization including the removal of ∼50 Mb from thousands of loci called internal eliminated sequences (IESs). IES-associated chromatin is methylated on lysines 9 and 27 of histone H3, marking newly formed heterochromatin for elimination. To ensure that this reorganized genome maintains essential coding and regulatory sequences, the boundaries of IESs must be accurately defined. In this study, we show that the developmentally expressed protein encoded by Lia3-Like 1 (LTL1) (Ttherm_00499370) is necessary to direct the excision boundaries of particular IESs. In ΔLTL1 cells, boundaries of eliminated loci are aberrant and heterogeneous. The IESs regulated by Ltl1 are distinct from those regulated by the guanine-quadruplex binding Lia3 protein. Ltl1 has a general affinity for double stranded DNA (Kd ∼ 350 nM) and binds specifically to a 50 bp A+T rich sequence flanking each side of the D IES (Kd ∼ 43 nM). Together these data reveal that Ltl1 and Lia3 control different subsets of IESs and that their mechanisms for flanking sequence recognition are distinct.
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Affiliation(s)
- Vita N Jaspan
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Marta E Taye
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Christine M Carle
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Joyce J Chung
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Douglas L Chalker
- Biology Department, Washington University in St. Louis, St. Louis, MO 63130, USA
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2
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Chidambaranathan-Reghupaty S, Mendoza R, Fisher PB, Sarkar D. The multifaceted oncogene SND1 in cancer: focus on hepatocellular carcinoma. ACTA ACUST UNITED AC 2018; 4. [PMID: 32258418 PMCID: PMC7117101 DOI: 10.20517/2394-5079.2018.34] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Staphylococcal nuclease and tudor domain containing 1 (SND1) is a protein that regulates a complex array of functions. It controls gene expression through transcriptional activation, mRNA degradation, mRNA stabilization, ubiquitination and alternative splicing. More than two decades of research has accumulated evidence of the role of SND1 as an oncogene in various cancers. It is a promoter of cancer hallmarks like proliferation, invasion, migration, angiogenesis and metastasis. In addition to these functions, it has a role in lipid metabolism, inflammation and stress response. The participation of SND1 in such varied functions makes it distinct from most oncogenes that are relatively more focused in their role. This becomes important in the case of hepatocellular carcinoma (HCC) since in addition to typical cancer drivers, factors like lipid metabolism deregulation and chronic inflammation can predispose hepatocytes to HCC. The objective of this review is to provide a summary of the current knowledge available on SND1, specifically in relation to HCC and to shed light on its prospect as a therapeutic target.
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Affiliation(s)
| | - Rachel Mendoza
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Paul B Fisher
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA.,Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, USA.,VCU Institute of Molecular Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Devanand Sarkar
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA.,Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, USA.,VCU Institute of Molecular Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
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3
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Noto T, Mochizuki K. Whats, hows and whys of programmed DNA elimination in Tetrahymena. Open Biol 2018; 7:rsob.170172. [PMID: 29021213 PMCID: PMC5666084 DOI: 10.1098/rsob.170172] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 09/12/2017] [Indexed: 12/20/2022] Open
Abstract
Programmed genome rearrangements in ciliates provide fascinating examples of flexible epigenetic genome regulations and important insights into the interaction between transposable elements (TEs) and host genomes. DNA elimination in Tetrahymena thermophila removes approximately 12 000 internal eliminated sequences (IESs), which correspond to one-third of the genome, when the somatic macronucleus (MAC) differentiates from the germline micronucleus (MIC). More than half of the IESs, many of which show high similarity to TEs, are targeted for elimination in cis by the small RNA-mediated genome comparison of the MIC to the MAC. Other IESs are targeted for elimination in trans by the same small RNAs through repetitive sequences. Furthermore, the small RNA–heterochromatin feedback loop ensures robust DNA elimination. Here, we review an updated picture of the DNA elimination mechanism, discuss the physiological and evolutionary roles of DNA elimination, and outline the key questions that remain unanswered.
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Affiliation(s)
- Tomoko Noto
- Institute of Human Genetics, UMR 9002, CNRS and University of Montpellier, Montpellier, France
| | - Kazufumi Mochizuki
- Institute of Human Genetics, UMR 9002, CNRS and University of Montpellier, Montpellier, France
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4
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Qiu GH, Huang C, Zheng X, Yang X. The protective function of noncoding DNA in genome defense of eukaryotic male germ cells. Epigenomics 2018; 10:499-517. [PMID: 29616594 DOI: 10.2217/epi-2017-0103] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Peripheral and abundant noncoding DNA has been hypothesized to protect the genome and the central protein-coding sequences against DNA damage in somatic genome. In the cytosol, invading exogenous nucleic acids may first be deactivated by small RNAs encoded by noncoding DNA via mechanisms similar to the prokaryotic CRISPR-Cas system. In the nucleus, the radicals generated by radiation in the cytosol, radiation energy and invading exogenous nucleic acids are absorbed, blocked and/or reduced by peripheral heterochromatin, and damaged DNA in heterochromatin is removed and excluded from the nucleus to the cytoplasm through nuclear pore complexes. To further strengthen the hypothesis, this review summarizes the experimental evidence supporting the protective function of noncoding DNA in the genome of male germ cells. Based on these data, this review provides evidence supporting the protective role of noncoding DNA in the genome defense of sperm genome through similar mechanisms to those of the somatic genome.
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Affiliation(s)
- Guo-Hua Qiu
- Fujian Provincial Key Laboratory for the Prevention & Control of Animal Infectious Diseases & Biotechnology; Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province University; College of Life Sciences, Longyan University, Longyan 364012, Fujian, PR China
| | - Cuiqin Huang
- Fujian Provincial Key Laboratory for the Prevention & Control of Animal Infectious Diseases & Biotechnology; Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province University; College of Life Sciences, Longyan University, Longyan 364012, Fujian, PR China
| | - Xintian Zheng
- Fujian Provincial Key Laboratory for the Prevention & Control of Animal Infectious Diseases & Biotechnology; Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province University; College of Life Sciences, Longyan University, Longyan 364012, Fujian, PR China
| | - Xiaoyan Yang
- Fujian Provincial Key Laboratory for the Prevention & Control of Animal Infectious Diseases & Biotechnology; Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province University; College of Life Sciences, Longyan University, Longyan 364012, Fujian, PR China
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5
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Xing A, Pan L, Gao J. p100 functions as a metastasis activator and is targeted by tumor suppressing microRNA-320a in lung cancer. Thorac Cancer 2018; 9:152-158. [PMID: 29159900 PMCID: PMC5754290 DOI: 10.1111/1759-7714.12564] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 10/23/2017] [Accepted: 10/23/2017] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Lung cancer is among the most frequently diagnosed types of cancer worldwide, with high morbidity and mortality. Metastasis accounts for the deadliest and most poorly understood feature of lung cancer. Herein, we demonstrate that SND1 (also known as p100) acts as a candidate metastasis activator and is targeted by microRNA-320a (miR-320a) in lung cancer cells. METHODS p100 expression in lung cancer cell lines and tissues was determined by quantitative real time-PCR and Western blot. RNA interference was applied to investigate the functions of p100 in lung cancer cell migration, reflected by wound healing and transwell assays. Luciferase reporter assay, quantitative real time-PCR, and Western blot were finally used to examine miR-320a targeting of p100 in lung cancer cells. RESULTS p100 expression was significantly higher in lung cancer cell lines and tissues compared to normal human bronchial epithelial cells and matched normal lung tissues. Downregulation of p100 by RNA interference obviously inhibited lung cancer cell migration in vitro. Moreover, we validated p100 as a direct target of miR-320a, a tumor suppressing microRNA repressing lung cancer cell migration. Finally, we showed an inversely expressed correlation between p100 and miR-320a in tested lung cancer tissues and cell lines, both of which acted as important prognostic factors in lung cancer. CONCLUSION Our findings identify that p100, targeted by tumor suppressing miR-320a, is a key metastasis activator in lung cancer, and both p100 and miR-320a could be considered as biomarkers for prognosis of lung cancer patients.
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Affiliation(s)
- Aimin Xing
- Respiratory DepartmentTianjin 4th Center HospitalTianjinChina
| | - Li Pan
- Respiratory DepartmentTianjin 4th Center HospitalTianjinChina
| | - Jingzhen Gao
- Respiratory DepartmentTianjin 4th Center HospitalTianjinChina
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6
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Chromodomain protein Tcd1 is required for macronuclear genome rearrangement and repair in Tetrahymena. Sci Rep 2015; 5:10243. [PMID: 25989344 PMCID: PMC4437310 DOI: 10.1038/srep10243] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 04/07/2015] [Indexed: 11/25/2022] Open
Abstract
The survival of an organism’s progeny depends on the maintenance of its genome. Programmed DNA rearrangement and repair in Tetrahymena occur during the differentiation of the developing somatic macronuclear genome from the germ line micronuclear genome. Tetrahymena chromodomain protein (Tcd1) exhibited dynamic localization from the parental to the developing macronuclei. In the developing macronuclei, Tcd1 colocalized with Pdd1 and H3K9me3. Furthermore, Tcd1 colocalized with Pdd1 in the conjusome and “donut structure” of DNA elimination heterochromatin region. During the growth and conjugation stages, TCD1 knockout cells appeared normal and similar to wild-type strains. In addition, these knockout cells proceeded to the 2MAC-1MIC stage. However, the progeny of the TCD1 knockout cells did not grow upon return to SPP medium and eventually died. The deletion of the internal elimination sequence R element was partially disrupted in the developing new macronuclei. Gamma H2A staining showed that Tcd1 loss induced the accumulation of DNA double-strand breaks and the failure of genome repair. These results suggest that the chromodomain protein Tcd1 is required for the rearrangement and repair of new macronuclear genome in Tetrahymena.
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7
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Gutierrez-Beltran E, Moschou PN, Smertenko AP, Bozhkov PV. Tudor staphylococcal nuclease links formation of stress granules and processing bodies with mRNA catabolism in Arabidopsis. THE PLANT CELL 2015; 27:926-43. [PMID: 25736060 PMCID: PMC4558657 DOI: 10.1105/tpc.114.134494] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 02/03/2015] [Accepted: 02/16/2015] [Indexed: 05/18/2023]
Abstract
Tudor Staphylococcal Nuclease (TSN or Tudor-SN; also known as SND1) is an evolutionarily conserved protein involved in the transcriptional and posttranscriptional regulation of gene expression in animals. Although TSN was found to be indispensable for normal plant development and stress tolerance, the molecular mechanisms underlying these functions remain elusive. Here, we show that Arabidopsis thaliana TSN is essential for the integrity and function of cytoplasmic messenger ribonucleoprotein (mRNP) complexes called stress granules (SGs) and processing bodies (PBs), sites of posttranscriptional gene regulation during stress. TSN associates with SGs following their microtubule-dependent assembly and plays a scaffolding role in both SGs and PBs. The enzymatically active tandem repeat of four SN domains is crucial for targeting TSN to the cytoplasmic mRNA complexes and is sufficient for the cytoprotective function of TSN during stress. Furthermore, our work connects the cytoprotective function of TSN with its positive role in stress-induced mRNA decapping. While stress led to a pronounced increase in the accumulation of uncapped mRNAs in wild-type plants, this increase was abrogated in TSN knockout plants. Taken together, our results establish TSN as a key enzymatic component of the catabolic machinery responsible for the processing of mRNAs in the cytoplasmic mRNP complexes during stress.
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Affiliation(s)
- Emilio Gutierrez-Beltran
- Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, SE-75007 Uppsala, Sweden
| | - Panagiotis N Moschou
- Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, SE-75007 Uppsala, Sweden
| | - Andrei P Smertenko
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164 Institute for Global Food Security, Queen's University Belfast, Belfast BT9 5BN, United Kingdom
| | - Peter V Bozhkov
- Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, SE-75007 Uppsala, Sweden
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8
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Gutiérrez-Beltran E, Bozhkov PV, Moschou PN. Tudor Staphylococcal Nuclease plays two antagonistic roles in RNA metabolism under stress. PLANT SIGNALING & BEHAVIOR 2015; 10:e1071005. [PMID: 26237081 PMCID: PMC4883894 DOI: 10.1080/15592324.2015.1071005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Adaptation to stress entails a repertoire of molecular pathways that remodel the proteome, thereby promoting selective translation of pro-survival proteins. Yet, translation of other proteins, especially those which are harmful for stress adaptation is, on the contrary, transiently suppressed through mRNA decay or storage. Proteome remodeling under stress is intimately associated with the cytoplasmic ribonucleoprotein (RNP) complexes called stress granules (SGs) and processing bodies (PBs). The molecular composition and regulation of SGs and PBs in plants remain largely unknown. Recently, we identified the Arabidopsis Tudor Staphylococcal Nuclease (TSN, Tudor-SN or SND1) as a SG- and PB-associated protein required for mRNA decapping under stress conditions. Here we show that SGs localize in close proximity to PBs within plant cells that enable the exchange of molecular components. Furthermore, we provide a meta-analysis of mRNA degradome of TSN-deficient plants suggesting that TSN might inhibit the degradation of mRNAs which are involved in stress adaptation. Our results establish TSN as a versatile mRNA regulator during stress.
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Affiliation(s)
- Emilio Gutiérrez-Beltran
- Department of Plant Biology and Department of Chemistry and Biotechnology; Uppsala BioCenter; Swedish University of Agricultural Sciences and Linnean Center for Plant Biology; Uppsala, Sweden
- Correspondence to: Emilio Gutiérrez-Beltran;
| | - Peter V Bozhkov
- Department of Plant Biology and Department of Chemistry and Biotechnology; Uppsala BioCenter; Swedish University of Agricultural Sciences and Linnean Center for Plant Biology; Uppsala, Sweden
| | - Panagiotis N Moschou
- Department of Plant Biology and Department of Chemistry and Biotechnology; Uppsala BioCenter; Swedish University of Agricultural Sciences and Linnean Center for Plant Biology; Uppsala, Sweden
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9
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Abstract
Research using ciliates revealed early examples of epigenetic phenomena and continues to provide novel findings. These protozoans maintain separate germline and somatic nuclei that carry transcriptionally silent and active genomes, respectively. Examining the differences in chromatin within distinct nuclei of Tetrahymena identified histone variants and established that transcriptional regulators act by modifying histones. Formation of somatic nuclei requires both transcriptional activation of silent chromatin and large-scale DNA elimination. This somatic genome remodeling is directed by homologous RNAs, acting with an RNA interference (RNAi)-related machinery. Furthermore, the content of the parental somatic genome provides a homologous template to guide this genome restructuring. The mechanisms regulating ciliate DNA rearrangements reveal the surprising power of homologous RNAs to remodel the genome and transmit information transgenerationally.
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Affiliation(s)
- Douglas L Chalker
- Department of Biology, Washington University, St. Louis, Missouri 63130
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10
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Zhu L, Tatsuke T, Mon H, Li Z, Xu J, Lee JM, Kusakabe T. Characterization of Tudor-sn-containing granules in the silkworm, Bombyx mori. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2013; 43:664-674. [PMID: 23643815 DOI: 10.1016/j.ibmb.2013.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/05/2013] [Accepted: 04/15/2013] [Indexed: 06/02/2023]
Abstract
The Tudor-sn protein, which contains four staphylococcal nuclease domains and a Tudor domain, is a ubiquitous protein found in almost all organisms. It has been reported that Tudor-sn in mammals participates in various cellular pathways involved in gene regulation, cell growth, and development. In insects, we have previously identified a Tudor-sn ortholog in the silkworm, Bombyx mori, and detected its interactions between with Argonaute proteins. The role of Tudor-sn in silkworm, however, still remains largely unknown. In this study, we demonstrated that silkworm Tudor-sn is a stress granule (SG) protein, and determined its interactions with other SG proteins using Bimolecular Fluorescence Complementation assay and Insect Two-Hybrid method. Depletions of Argonaute proteins and SG-marker protein Tia1 by RNAi impaired the involvement of Tudor-sn in the SG formation. Protein domain deletion analysis of Tudor-sn demonstrated that SN2 is the key domain required for the aggregation of Tudor-sn in SGs.
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Affiliation(s)
- Li Zhu
- Laboratory of Silkworm Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Sciences, Hakozaki 6-10-1, Fukuoka 812-8581, Japan
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11
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Stemm-Wolf AJ, Meehl JB, Winey M. Sfr13, a member of a large family of asymmetrically localized Sfi1-repeat proteins, is important for basal body separation and stability in Tetrahymena thermophila. J Cell Sci 2013; 126:1659-71. [PMID: 23426847 DOI: 10.1242/jcs.120238] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Directed fluid flow, which is achieved by the coordinated beating of motile cilia, is required for processes as diverse as cellular swimming, developmental patterning and mucus clearance. Cilia are nucleated, anchored and aligned at the plasma membrane by basal bodies, which are cylindrical microtubule-based structures with ninefold radial symmetry. In the unicellular ciliate Tetrahymena thermophila, two centrin family members associated with the basal body are important for both basal body organization and stabilization. We have identified a family of 13 proteins in Tetrahymena that contain centrin-binding repeats related to those identified in the Saccharomyces cerevisiae Sfi1 protein. We have named these proteins Sfr1-Sfr13 (for Sfi1-repeat). Nine of the Sfr proteins localize in unique polarized patterns surrounding the basal body, suggesting non-identical roles in basal body organization and association with basal body accessory structures. Furthermore, the Sfr proteins are found in distinct basal body populations in Tetrahymena cells, indicating that they are responsive to particular developmental programs. A complete genetic deletion of one of the family members, Sfr13, causes unstable basal bodies and defects in daughter basal body separation from the mother, phenotypes also observed with centrin disruption. It is likely that the other Sfr family members are involved in distinct centrin functions, providing specificity to the tasks that centrins perform at basal bodies.
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Affiliation(s)
- Alexander J Stemm-Wolf
- Department of Molecular, Cellular and Developmental Biology, University of Colorado - Boulder, Boulder, CO 80309, USA
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12
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Schoeberl UE, Kurth HM, Noto T, Mochizuki K. Biased transcription and selective degradation of small RNAs shape the pattern of DNA elimination in Tetrahymena. Genes Dev 2012; 26:1729-42. [PMID: 22855833 PMCID: PMC3418590 DOI: 10.1101/gad.196493.112] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 06/21/2012] [Indexed: 01/05/2023]
Abstract
The ciliated protozoan Tetrahymena undergoes extensive programmed DNA elimination when the germline micronucleus produces the new macronucleus during sexual reproduction. DNA elimination is epigenetically controlled by DNA sequences of the parental macronuclear genome, and this epigenetic regulation is mediated by small RNAs (scan RNAs [scnRNAs]) of ∼28-30 nucleotides that are produced and function by an RNAi-related mechanism. Here, we examine scnRNA production and turnover by deep sequencing. scnRNAs are produced exclusively from the micronucleus and nonhomogeneously from a variety of chromosomal locations. scnRNAs are preferentially derived from the eliminated sequences, and this preference is mainly determined at the level of transcription. Despite this bias, a significant fraction of scnRNAs is also derived from the macronuclear-destined sequences, and these scnRNAs are degraded during the course of sexual reproduction. These results indicate that the pattern of DNA elimination in the new macronucleus is shaped by the biased transcription in the micronucleus and the selective degradation of scnRNAs in the parental macronucleus.
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Affiliation(s)
| | | | | | - Kazufumi Mochizuki
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), A-1030 Vienna, Austria
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13
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Gao X, Zhao X, Zhu Y, He J, Shao J, Su C, Zhang Y, Zhang W, Saarikettu J, Silvennoinen O, Yao Z, Yang J. Tudor staphylococcal nuclease (Tudor-SN) participates in small ribonucleoprotein (snRNP) assembly via interacting with symmetrically dimethylated Sm proteins. J Biol Chem 2012; 287:18130-41. [PMID: 22493508 DOI: 10.1074/jbc.m111.311852] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Human Tudor staphylococcal nuclease (Tudor-SN) is composed of four tandem repeats of staphylococcal nuclease (SN)-like domains, followed by a tudor and SN-like domain (TSN) consisting of a central tudor flanked by two partial SN-like sequences. The crystal structure of the tudor domain displays a conserved aromatic cage, which is predicted to hook methyl groups. Here, we demonstrated that the TSN domain of Tudor-SN binds to symmetrically dimethylarginine (sDMA)-modified SmB/B' and SmD1/D3 core proteins of the spliceosome. We demonstrated that this interaction ability is reduced by the methyltransferase inhibitor 5-deoxy-5-(methylthio)adenosine. Mutagenesis experiments indicated that the conserved amino acids (Phe-715, Tyr-721, Tyr-738, and Tyr-741) in the methyl-binding cage of the TSN domain are required for Tudor-SN-SmB interaction. Furthermore, depletion of Tudor-SN affects the association of Sm protein with snRNAs and, as a result, inhibits the assembly of uridine-rich small ribonucleoprotein mediated by the Sm core complex in vivo. Our results reveal the molecular basis for the involvement of Tudor-SN in regulating small nuclear ribonucleoprotein biogenesis, which provides novel insight related to the biological activity of Tudor-SN.
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Affiliation(s)
- Xingjie Gao
- Department of Immunology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 30070, China
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14
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Abstract
Nuclear dualism is a characteristic feature of the ciliated protozoa. Tetrahymena have two different nuclei in each cell. The larger, polyploid, somatic macronucleus (MAC) is the site of transcriptional activity in the vegetatively growing cell. The smaller, diploid micronucleus (MIC) is transcriptionally inactive in vegetative cells, but is transcriptionally active in mating cells and responsible for the genetic continuity during sexual reproduction. Although the MICs and MACs develop from mitotic products of a common progenitor and reside in a common cytoplasm, they are different from one another in almost every respect.
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Affiliation(s)
- Kathleen M Karrer
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, USA
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15
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Mochizuki K. Developmentally programmed, RNA-directed genome rearrangement in Tetrahymena. Dev Growth Differ 2011; 54:108-19. [PMID: 22103557 DOI: 10.1111/j.1440-169x.2011.01305.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Developmentally programmed genome rearrangement has been observed in a variety of eukaryotes from vertebrates to worms to protists, and it provides an interesting exception to the general rule of the constancy of the genome. DNA elimination in the ciliated protozoan Tetrahymena is one of the most well-characterized programmed genome rearrangement events. DNA elimination in the newly formed macronucleus of Tetrahymena is epigenetically regulated by the DNA sequence of the parental macronucleus. Dicer-produced, Piwi-associated small RNAs mediate this epigenetic regulation, probably through a whole-genome comparison of the germline micronucleus to the somatic macronucleus. However, a correlation between small RNAs and programmed genome rearrangement could not be detected in the worm Ascaris suum. Therefore, different types of eukaryotes may have developed unique solutions to perform genome rearrangement.
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Affiliation(s)
- Kazufumi Mochizuki
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna, Austria.
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16
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Genome-Scale Analysis of Programmed DNA Elimination Sites in Tetrahymena thermophila. G3-GENES GENOMES GENETICS 2011; 1:515-22. [PMID: 22384362 PMCID: PMC3276166 DOI: 10.1534/g3.111.000927] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2011] [Accepted: 09/30/2011] [Indexed: 01/31/2023]
Abstract
Genetically programmed DNA rearrangements can regulate mRNA expression at an individual locus or, for some organisms, on a genome-wide scale. Ciliates rely on a remarkable process of whole-genome remodeling by DNA elimination to differentiate an expressed macronucleus (MAC) from a copy of the germline micronucleus (MIC) in each cycle of sexual reproduction. Here we describe results from the first high-throughput sequencing effort to investigate ciliate genome restructuring, comparing Sanger long-read sequences from a Tetrahymena thermophila MIC genome library to the MAC genome assembly. With almost 25% coverage of the unique-sequence MAC genome by MIC genome sequence reads, we created a resource for positional analysis of MIC-specific DNA removal that pinpoints MAC genome sites of DNA elimination at nucleotide resolution. The widespread distribution of internal eliminated sequences (IES) in promoter regions and introns suggests that MAC genome restructuring is essential not only for what it removes (for example, active transposons) but also for what it creates (for example, splicing-competent introns). Consistent with the heterogeneous boundaries and epigenetically modulated efficiency of individual IES deletions studied to date, we find that IES sites are dramatically under-represented in the ∼25% of the MAC genome encoding exons. As an exception to this general rule, we discovered a previously unknown class of small (<500 bp) IES with precise elimination boundaries that can contribute the 3′ exon of an mRNA expressed during genome restructuring, providing a new mechanism for expanding mRNA complexity in a developmentally regulated manner.
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17
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Alsford S, Kemp LE, Kawahara T, Horn D. RNA interference, growth and differentiation appear normal in African trypanosomes lacking Tudor staphylococcal nuclease. Mol Biochem Parasitol 2010; 174:70-3. [PMID: 20558212 PMCID: PMC2935966 DOI: 10.1016/j.molbiopara.2010.06.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 06/03/2010] [Accepted: 06/04/2010] [Indexed: 01/12/2023]
Abstract
Ribonucleases play important roles in the RNA interference (RNAi) pathway. The Dicer endonuclease converts double-stranded (ds)RNA into small interfering (si)RNA and the Slicer endonuclease, as a component of the RNA induced silencing complex (RISC), cleaves mRNA. Tudor staphylococcal nuclease (Tudor-SN) is another component of RISC in humans, flies and nematodes and is therefore implicated in the RNAi pathway. Here, we explore the potential role of African trypanosome Tudor-SN in RNAi. First, we assembled tudor-sn null mutants and showed that the gene is dispensable for normal growth and for differentiation. Next, we developed an inducible RNAi reporter system and demonstrated that Tudor-SN is dispensable for RNAi. The kinetics of mRNA knock-down, protein knock-down and protein recovery following inactivation of dsRNA expression are all unperturbed in the absence of Tudor-SN. We conclude that if this nuclease plays a role in the destruction or processing of dsRNA, mRNA or siRNA in the RNAi pathway, it is likely a minor one.
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Affiliation(s)
| | | | | | - David Horn
- Corresponding author. Tel.: +44 20 7927 2352.
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Huvos P. Varied truncation and clustering characterize some short repeats identified in micronucleus-specific DNA of Tetrahymena thermophila. Gene 2009; 448:174-9. [PMID: 19619624 DOI: 10.1016/j.gene.2009.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 07/07/2009] [Accepted: 07/12/2009] [Indexed: 10/20/2022]
Abstract
There are over 6000 internally eliminated DNA sequences (IESs) in the Tetrahymena genome that are deleted in a programmed fashion during the development of a polyploid, somatic macronucleus from a diploid germline micronucleus. Recently, based on several results, a homology and small RNA-based mechanism has been proposed for the efficient elimination of IES elements. Since the RNAi machinery is proposed to be intimately involved in silencing potentially harmful repeats such as transposons and viruses, characterization of repeats and the conditions for their developmental elimination from the somatic genome is warranted. Three short (500-600 bp) repeat families, members of which had been experimentally identified in IESs, that is, in micronucleus-specific DNA, are examined here using the Tetrahymena genome database. Members of all three families display varied degrees of truncation and are represented in macronuclear sequences. A 200 bp segment of one of the families can appear in the genome on its own, or as part of a 600 bp repeat detected experimentally, or in association with an unrelated 1 kb sequence to form a 1.2 kb repeat that is also frequently truncated. The 1 kb sequence contains a 300 bp section similar to a repeat associated with a non-long terminal repeat-like element and is often found accompanied by several more copies of this shorter repeat. These observations indicate that transposition may have had a role in the evolution of the short repeat families.
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Affiliation(s)
- Piroska Huvos
- Department of Biochemistry and Molecular Biology, Southern Illinois University, Carbondale, IL 62901-4413, USA.
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Zheng J, Lu J, Liu H, Li J, Chen K. Sequence and structural analysis of 4SNc-Tudor domain protein from Takifugu Rubripes. Bioinformation 2009; 4:127-31. [PMID: 20198186 PMCID: PMC2828898 DOI: 10.6026/97320630004127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 05/26/2009] [Accepted: 06/13/2009] [Indexed: 12/11/2022] Open
Abstract
The fugu SN4TDR protein belongs to an evolutionarily conserved family, consisting of four repeat staphylococcal nuclease-like domains (SN1-SN4) at the N-terminus followed by Tudor and SN-like domains (TSN). Sequence analysis showed that the C-terminal TSN domain is composed of a complete SN-like domain interdigitated with a Tudor domain. In despite of low level of sequence identities, five SN-like domains have a few conserved amino acids that may play essential roles in the function of the protein. Computer modeling and secondary structural prediction of the SN-like domains revealed the presence of similar structural features of beta1-beta2-beta3-alpha1-beta4-beta5-alpha2-alpha3, which provides a structural basis for oligonucleotides binding. The loop region L(3alpha) for binding sites between beta3 and alpha1 of SN-like domains are different from human p100, implying the divergence in the structures of binding sites. These results indicate that fugu SN4TDR may bind methylated ligands and/or oligonucleotides through its distant domains.
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Affiliation(s)
- Jianzhou Zheng
- Institute of life science, Jiangsu University, Zhenjiang, China
| | - Jian Lu
- Institute of life science, Jiangsu University, Zhenjiang, China
| | - Haijun Liu
- Institute of life science, Jiangsu University, Zhenjiang, China
| | - Jun Li
- Physical and Chemical Analysis Center, Jiangsu University, Zhenjiang, China
| | - Keping Chen
- Institute of life science, Jiangsu University, Zhenjiang, China
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Li CL, Yang WZ, Chen YP, Yuan HS. Structural and functional insights into human Tudor-SN, a key component linking RNA interference and editing. Nucleic Acids Res 2008; 36:3579-89. [PMID: 18453631 PMCID: PMC2441809 DOI: 10.1093/nar/gkn236] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Human Tudor-SN is involved in the degradation of hyper-edited inosine-containing microRNA precursors, thus linking the pathways of RNA interference and editing. Tudor-SN contains four tandem repeats of staphylococcal nuclease-like domains (SN1–SN4) followed by a tudor and C-terminal SN domain (SN5). Here, we showed that Tudor-SN requires tandem repeats of SN domains for its RNA binding and cleavage activity. The crystal structure of a 64-kD truncated form of human Tudor-SN further shows that the four domains, SN3, SN4, tudor and SN5, assemble into a crescent-shaped structure. A concave basic surface formed jointly by SN3 and SN4 domains is likely involved in RNA binding, where citrate ions are bound at the putative RNase active sites. Additional modeling studies provide a structural basis for Tudor-SN's preference in cleaving RNA containing multiple I·U wobble-paired sequences. Collectively, these results suggest that tandem repeats of SN domains in Tudor-SN function as a clamp to capture RNA substrates.
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Affiliation(s)
- Chia-Lung Li
- Institute of Molecular Biology, Academia Sinica and Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC
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