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Long Non-Coding RNAs in the Regulation of Gene Expression: Physiology and Disease. Noncoding RNA 2019; 5:ncrna5010017. [PMID: 30781588 PMCID: PMC6468922 DOI: 10.3390/ncrna5010017] [Citation(s) in RCA: 371] [Impact Index Per Article: 74.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/11/2019] [Accepted: 02/12/2019] [Indexed: 02/07/2023] Open
Abstract
The identification of RNAs that are not translated into proteins was an important breakthrough, defining the diversity of molecules involved in eukaryotic regulation of gene expression. These non-coding RNAs can be divided into two main classes according to their length: short non-coding RNAs, such as microRNAs (miRNAs), and long non-coding RNAs (lncRNAs). The lncRNAs in association with other molecules can coordinate several physiological processes and their dysfunction may impact in several pathologies, including cancer and infectious diseases. They can control the flux of genetic information, such as chromosome structure modulation, transcription, splicing, messenger RNA (mRNA) stability, mRNA availability, and post-translational modifications. Long non-coding RNAs present interaction domains for DNA, mRNAs, miRNAs, and proteins, depending on both sequence and secondary structure. The advent of new generation sequencing has provided evidences of putative lncRNAs existence; however, the analysis of transcriptomes for their functional characterization remains a challenge. Here, we review some important aspects of lncRNA biology, focusing on their role as regulatory elements in gene expression modulation during physiological and disease processes, with implications in host and pathogens physiology, and their role in immune response modulation.
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van Luenen HGAM, Farris C, Jan S, Genest PA, Tripathi P, Velds A, Kerkhoven RM, Nieuwland M, Haydock A, Ramasamy G, Vainio S, Heidebrecht T, Perrakis A, Pagie L, van Steensel B, Myler PJ, Borst P. Glucosylated hydroxymethyluracil, DNA base J, prevents transcriptional readthrough in Leishmania. Cell 2012; 150:909-21. [PMID: 22939620 DOI: 10.1016/j.cell.2012.07.030] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 05/16/2012] [Accepted: 07/25/2012] [Indexed: 12/25/2022]
Abstract
Some Ts in nuclear DNA of trypanosomes and Leishmania are hydroxylated and glucosylated to yield base J (β-D-glucosyl-hydroxymethyluracil). In Leishmania, about 99% of J is located in telomeric repeats. We show here that most of the remaining J is located at chromosome-internal RNA polymerase II termination sites. This internal J and telomeric J can be reduced by a knockout of J-binding protein 2 (JBP2), an enzyme involved in the first step of J biosynthesis. J levels are further reduced by growing Leishmania JBP2 knockout cells in BrdU-containing medium, resulting in cell death. The loss of internal J in JBP2 knockout cells is accompanied by massive readthrough at RNA polymerase II termination sites. The readthrough varies between transcription units but may extend over 100 kb. We conclude that J is required for proper transcription termination and infer that the absence of internal J kills Leishmania by massive readthrough of transcriptional stops.
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Affiliation(s)
- Henri G A M van Luenen
- Division of Molecular Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Apoptosis-like programmed cell death induces antisense ribosomal RNA (rRNA) fragmentation and rRNA degradation in Leishmania. Cell Death Differ 2012; 19:1972-82. [PMID: 22767185 PMCID: PMC3504711 DOI: 10.1038/cdd.2012.85] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Few natural antisense (as) RNAs have been reported as yet in the unicellular protozoan Leishmania. Here, we describe that Leishmania produces natural asRNAs complementary to all ribosomal RNA (rRNA) species. Interestingly, we show that drug-induced apoptosis-like programmed cell death triggers fragmentation of asRNA complementary to the large subunit gamma (LSU-γ) rRNA, one of the six 28S rRNA processed fragments in Leishmania. Heat and oxidative stress also induce fragmentation of asrRNA, but to a lesser extent. Extensive asrRNA cleavage correlates with rRNA breakdown and translation inhibition. Indeed, overexpression of asLSU-γ rRNA accelerates rRNA degradation upon induction of apoptosis. In addition, we provide mechanistic insight into the regulation of apoptosis-induced asrRNA fragmentation by a 67 kDa ATP-dependent RNA helicase of the DEAD-box subfamily. This helicase binds both sense (s)LSU-γ and asLSU-γ rRNAs, and appears to have a key role in protecting rRNA from degradation by preventing asrRNA cleavage and thus cell death. Remarkably, the asrRNA fragmentation process operates not only in trypanosomatid protozoa but also in mammals. Our findings uncover a novel mechanism of regulation involving asrRNA fragmentation and rRNA breakdown, that is triggered by apoptosis and conditions of reduced translation under stress, and seems to be evolutionary conserved.
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Smandi S, Guerfali FZ, Farhat M, Ben-Aissa K, Laouini D, Guizani-Tabbane L, Dellagi K, Benkahla A. Methodology optimizing SAGE library tag-to-gene mapping: application to Leishmania. BMC Res Notes 2012; 5:74. [PMID: 22283878 PMCID: PMC3292834 DOI: 10.1186/1756-0500-5-74] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 01/27/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Leishmaniasis are widespread parasitic-diseases with an urgent need for more active and less toxic drugs and for effective vaccines. Understanding the biology of the parasite especially in the context of host parasite interaction is a crucial step towards such improvements in therapy and control. Several experimental approaches including SAGE (Serial analysis of gene expression) have been developed in order to investigate the parasite transcriptome organisation and plasticity. Usual SAGE tag-to-gene mapping techniques are inadequate because almost all tags are normally located in the 3'-UTR outside the CDS, whereas most information available for Leishmania transcripts is restricted to the CDS predictions. The aim of this work is to optimize a SAGE libraries tag-to-gene mapping technique and to show how this development improves the understanding of Leishmania transcriptome. FINDINGS The in silico method implemented herein was based on mapping the tags to Leishmania genome using BLAST then mapping the tags to their gene using a data-driven probability distribution. This optimized tag-to-gene mappings improved the knowledge of Leishmania genome structure and transcription. It allowed analyzing the expression of a maximal number of Leishmania genes, the delimitation of the 3' UTR of 478 genes and the identification of biological processes that are differentially modulated during the promastigote to amastigote differentiation. CONCLUSION The developed method optimizes the assignment of SAGE tags in trypanosomatidae genomes as well as in any genome having polycistronic transcription and small intergenic regions.
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Affiliation(s)
- Sondos Smandi
- Laboratoire d'Immuno-Pathologie, Vaccinologie et Génétique Moléculaire (LIVGM), WHO Collaborating Center for Research and Training in Leishmaniasis, Institut Pasteur de Tunis, 13 place Pasteur BP74 1002, Tunis, Tunisia.
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Lye LF, Owens K, Shi H, Murta SMF, Vieira AC, Turco SJ, Tschudi C, Ullu E, Beverley SM. Retention and loss of RNA interference pathways in trypanosomatid protozoans. PLoS Pathog 2010; 6:e1001161. [PMID: 21060810 PMCID: PMC2965760 DOI: 10.1371/journal.ppat.1001161] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 09/23/2010] [Indexed: 01/02/2023] Open
Abstract
RNA interference (RNAi) pathways are widespread in metaozoans but the genes required show variable occurrence or activity in eukaryotic microbes, including many pathogens. While some Leishmania lack RNAi activity and Argonaute or Dicer genes, we show that Leishmania braziliensis and other species within the Leishmania subgenus Viannia elaborate active RNAi machinery. Strong attenuation of expression from a variety of reporter and endogenous genes was seen. As expected, RNAi knockdowns of the sole Argonaute gene implicated this protein in RNAi. The potential for functional genetics was established by testing RNAi knockdown lines lacking the paraflagellar rod, a key component of the parasite flagellum. This sets the stage for the systematic manipulation of gene expression through RNAi in these predominantly diploid asexual organisms, and may also allow selective RNAi-based chemotherapy. Functional evolutionary surveys of RNAi genes established that RNAi activity was lost after the separation of the Leishmania subgenus Viannia from the remaining Leishmania species, a divergence associated with profound changes in the parasite infectious cycle and virulence. The genus Leishmania therefore offers an accessible system for testing hypothesis about forces that may select for the loss of RNAi during evolution, such as invasion by viruses, changes in genome plasticity mediated by transposable elements and gene amplification (including those mediating drug resistance), and/or alterations in parasite virulence. RNAi interference pathways play fundamental roles in eukaryotes and provide important methods for the analysis of gene function. Occasionally RNAi has been lost, precluding its use as a tool, as well as raising the question of what forces could lead to loss of such a key pathway. Genomic and functional studies previously showed that within trypanosomatids protozoans RNAi was absent in both Leishmania major and Trypanosoma cruzi. The genome of L. braziliensis, a member of the early diverging Leishmania subgenus Viannia, retained key genes required for RNAi such as an Argonaute. We demonstrated that in fact L. braziliensis shows strong RNAi activity with reporter and endogenous genes affecting flagellar function. These data suggest that RNAi may be productively applied for functional genomic studies in L. braziliensis. We mapped the evolutionary point at which RNAi was lost in lineage leading to Leishmania and Crithidia, and establish that RNAi must have been lost at least twice in the trypanosomatids, once on the lineage leading to T. cruzi and independently following the divergence of the Viannia subgenus from other Leishmania species. Lastly, we discuss hypotheses concerning the forces leading to the loss of RNAi in Leishmania evolution, including viral invasion, increased genome plasticity, and altered virulence.
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Affiliation(s)
- Lon-Fye Lye
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Katherine Owens
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Huafang Shi
- Department of Internal Medicine, Yale University Medical School, New Haven, Connecticut, United States of America
| | - Silvane M. F. Murta
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Ana Carolina Vieira
- Department of Biochemistry, University of Kentucky Medical Center, Lexington, Kentucky, United States of America
| | - Salvatore J. Turco
- Department of Biochemistry, University of Kentucky Medical Center, Lexington, Kentucky, United States of America
| | - Christian Tschudi
- Department of Internal Medicine, Yale University Medical School, New Haven, Connecticut, United States of America
- Department of Epidemiology & Public Health, Yale University Medical School, New Haven, Connecticut, United States of America
| | - Elisabetta Ullu
- Department of Internal Medicine, Yale University Medical School, New Haven, Connecticut, United States of America
- Department of Cell Biology, Yale University Medical School, New Haven, Connecticut, United States of America
| | - Stephen M. Beverley
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
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Müller M, Padmanabhan PK, Papadopoulou B. Selective inactivation of SIDER2 retroposon-mediated mRNA decay contributes to stage- and species-specific gene expression in Leishmania. Mol Microbiol 2010; 77:471-91. [PMID: 20497500 DOI: 10.1111/j.1365-2958.2010.07226.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Despite their high genomic synteny, the Leishmania major and Leishmania infantum species exhibit extensive differences in mRNA expression patterns throughout the parasite's development. Yet, the underlying mechanisms for this species-specific differential gene expression are largely unknown. Here we report that Short Interspersed DEgenerated Retroposons of the SIDER2 subfamily, shown previously to promote rapid mRNA turnover, confer differential regulation of orthologous transcripts resulting in a stage- and species-specific gene expression. We demonstrate that SIDER2-mediated decay of two L. major transcripts encoding a hypothetical protein and an aminomethyltransferase to a similar extent in promastigote and amastigote developmental forms results in a constitutive low expression of the corresponding proteins. In contrast, their L. infantum orthologs are differentially expressed due to the selective inactivation of SIDER2 in intracellular amastigotes. Inactivation of the SIDER2 function blocks the SIDER2-mediated deadenylation-independent decay pathway, and stabilized transcripts are degraded by a slower, deadenylation-dependent mechanism. Sequence variations in SIDER2 retroposons between orthologous transcripts do not contribute to SIDER2 inactivation. Our data suggest that SIDER2 inactivation is 3'-untranslated region context-dependent and that involves possibly species- and stage-specific trans-acting factor(s). These findings further emphasize the important contribution of SIDER retroposons in the control of gene expression across the Leishmania genus.
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Affiliation(s)
- Michaela Müller
- Infectious Disease Research Center, CHUL Research Center and Department of Microbiology and Immunology, Faculty of Medicine, Laval University, Quebec, Canada
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Müller M, Padmanabhan PK, Rochette A, Mukherjee D, Smith M, Dumas C, Papadopoulou B. Rapid decay of unstable Leishmania mRNAs bearing a conserved retroposon signature 3'-UTR motif is initiated by a site-specific endonucleolytic cleavage without prior deadenylation. Nucleic Acids Res 2010; 38:5867-83. [PMID: 20453029 PMCID: PMC2943621 DOI: 10.1093/nar/gkq349] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
We have previously shown that the Leishmania genome possess two widespread families of extinct retroposons termed Short Interspersed DEgenerated Retroposons (SIDER1/2) that play a role in post-transcriptional regulation. Moreover, we have demonstrated that SIDER2 retroposons promote mRNA degradation. Here we provide new insights into the mechanism by which unstable Leishmania mRNAs harboring a SIDER2 retroposon in their 3′-untranslated region are degraded. We show that, unlike most eukaryotic transcripts, SIDER2-bearing mRNAs do not undergo poly(A) tail shortening prior to rapid turnover, but instead, they are targeted for degradation by a site-specific endonucleolytic cleavage. The main cleavage site was mapped in two randomly selected SIDER2-containing mRNAs in vivo between an AU dinucleotide at the 5′-end of the second 79-nt signature (signature II), which represents the most conserved sequence amongst SIDER2 retroposons. Deletion of signature II abolished endonucleolytic cleavage and deadenylation-independent decay and increased mRNA stability. Interestingly, we show that overexpression of SIDER2 anti-sense RNA can increase sense transcript abundance and stability, and that complementarity to the cleavage region is required for protecting SIDER2-containing transcripts from degradation. These results establish a new paradigm for how unstable mRNAs are degraded in Leishmania and could serve as the basis for a better understanding of mRNA decay pathways in general.
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Affiliation(s)
- Michaela Müller
- Infectious Disease Research Centre, CHUL Research Centre and Department of Microbiology and Immunology, Faculty of Medicine, Laval University, Quebec, Canada
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Militello KT, Refour P, Comeaux CA, Duraisingh MT. Antisense RNA and RNAi in protozoan parasites: working hard or hardly working? Mol Biochem Parasitol 2007; 157:117-26. [PMID: 18053590 DOI: 10.1016/j.molbiopara.2007.10.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Revised: 10/11/2007] [Accepted: 10/12/2007] [Indexed: 10/22/2022]
Abstract
The complex life cycles of many protozoan parasites require the ability to respond to environmental and developmental cues through regulated gene expression. Traditionally, parasitologists have investigated these mechanisms by identifying and characterizing proteins that are necessary for the regulated expression of the genetic material. Although often successful, it is clear that protein-mediated gene regulation is only part of a complex story in which RNA itself is endowed with regulatory functions. Herein, we review both the known and potential regulatory roles of two types of RNA pathways within protozoan parasites: the RNA interference pathway and natural antisense transcripts. A better understanding of the native role of these pathways will not only enhance our understanding of the biology of these organisms but also aid in the development of more robust tools for reverse genetic analysis in this post-genomic era.
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Affiliation(s)
- Kevin T Militello
- Department of Biology, State University of New York at Geneseo, Geneseo, NY, USA
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Dumas C, Chow C, Müller M, Papadopoulou B. A novel class of developmentally regulated noncoding RNAs in Leishmania. EUKARYOTIC CELL 2006; 5:2033-46. [PMID: 17071827 PMCID: PMC1694821 DOI: 10.1128/ec.00147-06] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Leishmania is a protozoan parasite that causes serious morbidity and mortality in humans worldwide. The ability of these parasites to survive within the phagolysosomes of mammalian macrophages is dependent on the developmental regulation of a variety of genes. Identifying genomic sequences that are preferentially expressed during the parasite's intracellular growth would provide new insights about the mechanisms controlling stage-specific gene regulation for intracellular development of the parasite. Using a genomic library that differentially hybridized to probes made from total RNA from Leishmania infantum amastigote or promastigote life cycle stages, we identified a new class of noncoding RNAs (ncRNAs) ranging from approximately 300 to 600 nucleotides in size that are expressed specifically in the intracellular amastigote stage. These ncRNAs are transcribed by RNA polymerase II from genomic clusters of tandem head-to-tail repeats, which are mainly located within subtelomeric regions. Remarkably, both the sense and antisense orientations of these ncRNAs are transcribed and are processed by trans splicing and polyadenylation. The levels of antisense transcripts are at least 10-fold lower than those of the sense transcripts and are tightly regulated. The sense and antisense ncRNAs are cytosolic as shown by fluorescence in situ hybridization studies and cosediment with a small ribonucleoprotein complex. Amastigote-specific regulation of these ncRNAs possibly occurs at the level of RNA stability. Interestingly, overexpression of these ncRNAs in promastigotes, as part of an episomal expression vector, failed to produce any transcript, which further highlights the instability of these RNAs in the promastigote stage. This is the first report describing developmentally regulated ncRNAs in protozoan parasites.
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Affiliation(s)
- Carole Dumas
- Infectious Diseases Research Center, CHUL Research Center, CHUQ, Laval University, 2705 Laurier Blvd., Quebec, Canada G1V 4G2
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Rosenzvit MC, Zhang W, Motazedian H, Smyth D, Pearson M, Loukas A, Jones MK, McManus DP. Identification of membrane-bound and secreted proteins from Echinococcus granulosus by signal sequence trap. Int J Parasitol 2006; 36:123-30. [PMID: 16229848 DOI: 10.1016/j.ijpara.2005.09.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Revised: 08/14/2005] [Accepted: 09/07/2005] [Indexed: 10/25/2022]
Abstract
The signal sequence trap technique was applied to identify genes coding for secreted and membrane bound proteins from Echinococcus granulosus, the etiologic agent of cystic hydatid disease. An E. granulosus protoscolex cDNA library was constructed in the AP-PST vector such that randomly primed cDNAs were fused with a placental alkaline phosphatase reporter gene lacking its endogenous signal peptide. E. granulosus cDNAs encoding a functional signal peptide were selected by their ability to rescue secretion of alkaline phosphatase by COS-7 cells that had been transfected with the cDNA library. Eighteen positive clones were identified and sequenced. Their deduced amino acid sequences showed significant similarity with amino acid transporters, Krebs cycle intermediates transporters, presenilins and vacuolar protein sorter proteins. Other cDNAs encoded secreted proteins without homologues. Three sequences were transcribed antisense to E. granulosus expressed sequence tags. All the mRNAs were expressed in protoscoleces and adult worms, but some of them were not found in oncospheres. The putative E. granulosus secreted and membrane bound proteins identified are likely to play important roles in the metabolism, development and survival in the host and represent potential targets for diagnosis, drugs and vaccines against E. granulosus.
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Affiliation(s)
- Mara C Rosenzvit
- Queensland Institute of Medical Research, 300 Herston Road, Herston, Brisbane, Qld 4029, Australia.
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Nishida H, Tomaru Y, Oho Y, Hayashizaki Y. Naturally occurring antisense RNA of histone H2a in mouse cultured cell lines. BMC Genet 2005; 6:23. [PMID: 15892893 PMCID: PMC1156883 DOI: 10.1186/1471-2156-6-23] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2004] [Accepted: 05/14/2005] [Indexed: 11/30/2022] Open
Abstract
Background An antisense transcript of histone H2a that has no significant protein-coding region has been cloned from a mouse full-length cDNA library. In the present study, we evaluated this transcript by using RT-PCR and compared the expression patterns of the sense and antisense transcripts by using quantitative RT-PCR (qRT-PCR). Results This antisense RNA was expressed in three mouse cell lines. We call it ASH2a. ASH2a includes not only the complementary sequence of the transcript of Hist2h2aa2 (a replication-dependent histone H2a gene), but also that of the promoter of Hist2h2aa2. The upstream genomic sequence of the transcription start site of the ASH2a-coding gene (ASH2a) lacks both CCAAT and TATA boxes. This absence suggests that the regulation of ASH2a is different from that of the replication-dependent histone H2a genes. Findings from qRT-PCR indicated that the expression pattern of ASH2a was different from that of Hist2h2aa2. Expression of Hist2h2aa2 peaked at 2 to 4 h during S-phase, but that of ASH2a peaked at 1 h. Conclusion We showed the existence of ASH2a, a histone H2a antisense RNA, in mouse cultured cells. The expression pattern of ASH2a is different from that of the sense RNA.
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Affiliation(s)
- Hiromi Nishida
- Laboratory for Genome Exploration Research Group, RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Yasuhiro Tomaru
- Laboratory for Genome Exploration Research Group, RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Yuko Oho
- Laboratory for Genome Exploration Research Group, RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Yoshihide Hayashizaki
- Laboratory for Genome Exploration Research Group, RIKEN Genomic Sciences Center (GSC), RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
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Monnerat S, Martinez-Calvillo S, Worthey E, Myler PJ, Stuart KD, Fasel N. Genomic organization and gene expression in a chromosomal region of Leishmania major. Mol Biochem Parasitol 2004; 134:233-43. [PMID: 15003843 DOI: 10.1016/j.molbiopara.2003.12.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2003] [Revised: 11/27/2003] [Accepted: 12/11/2003] [Indexed: 11/29/2022]
Abstract
Little is known about the relation between the genome organization and gene expression in Leishmania. Bioinformatic analysis can be used to predict genes and find homologies with known proteins. A model was proposed, in which genes are organized into large clusters and transcribed from only one strand, in the form of large polycistronic primary transcripts. To verify the validity of this model, we studied gene expression at the transcriptional, post-transcriptional and translational levels in a unique locus of 34kb located on chr27 and represented by cosmid L979. Sequence analysis revealed 115 ORFs on either DNA strand. Using computer programs developed for Leishmania genes, only nine of these ORFs, localized on the same strand, were predicted to code for proteins, some of which show homologies with known proteins. Additionally, one pseudogene, was identified. We verified the biological relevance of these predictions. mRNAs from nine predicted genes and proteins from seven were detected. Nuclear run-on analyses confirmed that the top strand is transcribed by RNA polymerase II and suggested that there is no polymerase entry site. Low levels of transcription were detected in regions of the bottom strand and stable transcripts were identified for four ORFs on this strand not predicted to be protein-coding. In conclusion, the transcriptional organization of the Leishmania genome is complex, raising the possibility that computer predictions may not be comprehensive.
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Affiliation(s)
- Séverine Monnerat
- Department of Biochemistry, University of Lausanne, Ch. des Boveresses 155, 1066 Epalinges, Switzerland
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Akopyants NS, Matlib RS, Bukanova EN, Smeds MR, Brownstein BH, Stormo GD, Beverley SM. Expression profiling using random genomic DNA microarrays identifies differentially expressed genes associated with three major developmental stages of the protozoan parasite Leishmania major. Mol Biochem Parasitol 2004; 136:71-86. [PMID: 15138069 DOI: 10.1016/j.molbiopara.2004.03.002] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2004] [Revised: 03/08/2004] [Accepted: 03/09/2004] [Indexed: 11/19/2022]
Abstract
To complete its life cycle, protozoan parasites of the genus Leishmania undergo at least three major developmental transitions. However, previous efforts to identify genes showing stage regulated changes in transcript abundance have yielded relatively few. Here we used expression profiling to assess changes in transcript abundance in three stages: replicating promastigotes and infective non-replicating metacyclics, which occur in the sand fly vector, and in the amastigote stage residing with macrophage phagolysosomes in mammals. Microarrays were developed containing 11,484 PCR products that included a number of known genes and 10,464 random 1 kb genomic DNA fragments. Arrays were hybridized in triplicate and genes showing two-fold or greater changes in 2/3 experiments were scored as differentially expressed. Remarkably, only about one percent of the DNAs expression varied by this criteria, in either stage comparison. Northern blot analysis confirmed the predicted change in mRNA abundance for most of these (68%). This set of genes included most of those previously identified in the literature as differentially regulated as well as a number of novel genes. Notably, Leishmania maxicircle transcripts showed strong up-regulation in metacyclic and amastigote parasites, probably associated with changes in parasite energy metabolism. However, current data suggest that expression profiling using shotgun DNA libraries significantly underestimates the extent of regulated transcripts.
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Affiliation(s)
- Natalia S Akopyants
- Department of Molecular Microbiology, Center for Infectious Disease Research, Washington University School of Medicine, Campus Box 8230, 660 South Euclid Avenue, Saint Louis, MO 63110, USA
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Martínez-Calvillo S, Yan S, Nguyen D, Fox M, Stuart K, Myler PJ. Transcription of Leishmania major Friedlin chromosome 1 initiates in both directions within a single region. Mol Cell 2003; 11:1291-9. [PMID: 12769852 DOI: 10.1016/s1097-2765(03)00143-6] [Citation(s) in RCA: 215] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Almost nothing is known about the sequences involved in transcription initiation of protein-coding genes in the parasite Leishmania. We describe here the transcriptional analysis of chromosome 1 (chr1) from Leishmania major Friedlin (LmjF) which encodes the first 29 genes on one DNA strand, and the remaining 50 on the opposite strand. Strand-specific nuclear run-on assays showed that a low level of nonspecific transcription probably takes place over the entire chromosome, but an approximately 10-fold higher level of coding strand-specific RNA polymerase II (Pol II)-mediated transcription initiates within the strand-switch region. 5' RACE studies localized the initiation sites to a <100 bp region. Transfection studies support the presence of a bidirectional promoter within the strand-switch region, but suggest that other factors are also involved in Pol II transcription. Thus, while in most eukaryotes each gene possesses its own promoter, a single region seems to drive the expression of the entire chr1 in LmjF.
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Affiliation(s)
- Santiago Martínez-Calvillo
- Seattle Biomedical Research Institute, and Department of Pathobiology, University of Washington, Seattle, WA 98109, USA
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