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Nepomuceno-Mejía T, Florencio-Martínez LE, Pineda-García I, Martínez-Calvillo S. Identification of factors involved in ribosome assembly in the protozoan parasite Leishmania major. Acta Trop 2022; 228:106315. [PMID: 35041807 DOI: 10.1016/j.actatropica.2022.106315] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 01/07/2022] [Accepted: 01/13/2022] [Indexed: 01/23/2023]
Abstract
Formation of the ribosome subunits is a complex and progressive cellular process that requires a plethora of non-ribosomal transient proteins and diverse small nucleolar RNAs, which are involved from the synthesis of the precursor ribosomal RNA in the nucleolus to the final ribosome processing steps in the cytoplasm. Employing PTP-tagged Nop56 as a fishing bait to capture pre-ribosomal particles by tandem affinity purifications, mass spectrometry assays and a robust in silico analysis, here we describe tens of ribosome assembly factors involved in the synthesis of both ribosomal subunits in the human pathogen Leishmania major, where the knowledge about ribosomal biogenesis is scarce. We identified a large number of proteins that participate in most stages of ribosome biogenesis in yeast and mammals. Among them, we found several putative orthologs of factors not previously identified in L. major, such as t-Utp4, t-Utp5, Rrp7, Nop9 and Nop15. Even more interesting is the fact that we identified several novel candidates that could participate in the assembly of the atypical 60S subunit in L. major, which contains eight different rRNA species. As these proteins do not seem to have a human counterpart, they have potential as targets for novel anti-leishmanial drugs. Also, numerous proteins whose function is not apparently linked to ribosome assembly were copurified, suggesting that the L. major nucleolus is a multifunctional nuclear body.
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Zhuang Y, Zhang H, Lin S. Polyadenylation of 18S rRNA in algae(1). JOURNAL OF PHYCOLOGY 2013; 49:570-579. [PMID: 27007045 DOI: 10.1111/jpy.12068] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 12/23/2012] [Indexed: 06/05/2023]
Abstract
Polyadenylation is best known for occurring to mRNA of eukaryotes transcribed by RNA polymerase II to stabilize mRNA molecules and promote their translation. rRNAs transcribed by RNA polymerase I or III are typically believed not to be polyadenylated. However, there is increasing evidence that polyadenylation occurs to nucleus-encoded rRNAs as part of the RNA degradation pathway. To examine whether the same polyadenylation-assisted degradation pathway occurs in algae, we surveyed representative species of algae including diatoms, chlorophytes, dinoflagellates and pelagophytes using oligo (dT)-primed reversed transcription PCR (RT-PCR). In all the algal species examined, truncated 18S rRNA or its precursor molecules with homo- or hetero-polymeric poly(A) tails were detected. Mining existing algal expressed sequence tag (EST) data revealed polyadenylated truncated 18S rRNA in four additional phyla of algae. rRNA polyadenylation occurred at various internal positions along the 18S rRNA and its precursor sequences. Moreover, putative homologs of noncanonical poly(A) polymerase (ncPAP) Trf4p, which is responsible for polyadenylating nuclear-encoded RNA and targeting it for degradation, were detected from the genomes and transcriptomes of five phyla of algae. Our results suggest that polyadenylation-assisted RNA degradation mechanism widely exists in algae, particularly for the nucleus-encoded rRNA and its precursors.
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Affiliation(s)
- Yunyun Zhuang
- Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340, USA
- Marine Biodiversity and Global Change Research Center and State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361005, China
| | - Huan Zhang
- Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340, USA
| | - Senjie Lin
- Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340, USA
- Marine Biodiversity and Global Change Research Center and State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361005, China
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Mayer MG, Santos MGD, Silva MFLD, Floeter-Winter LM. Footprints of a trypanosomatid RNA world: pre-small subunit rRNA processing by spliced leader addition trans-splicing. Mem Inst Oswaldo Cruz 2013; 107:522-31. [PMID: 22666864 DOI: 10.1590/s0074-02762012000400013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 01/11/2012] [Indexed: 11/22/2022] Open
Abstract
The addition of a capped mini-exon [spliced leader (SL)] through trans-splicing is essential for the maturation of RNA polymerase (pol) II-transcribed polycistronic pre-mRNAs in all members of the Trypanosomatidae family. This process is an inter-molecular splicing reaction that follows the same basic rules of cis-splicing reactions. In this study, we demonstrated that mini-exons were added to precursor ribosomal RNA (pre-rRNA) are transcribed by RNA pol I, including the 5' external transcribed spacer (ETS) region. Additionally, we detected the SL-5'ETS molecule using three distinct methods and located the acceptor site between two known 5'ETS rRNA processing sites (A' and A1) in four different trypanosomatids. Moreover, we detected a polyadenylated 5'ETS upstream of the trans-splicing acceptor site, which also occurs in pre-mRNA trans-splicing. After treatment with an indirect trans-splicing inhibitor (sinefungin), we observed SL-5'ETS decay. However, treatment with 5-fluorouracil (a precursor of RNA synthesis that inhibits the degradation of pre-rRNA) led to the accumulation of SL-5'ETS, suggesting that the molecule may play a role in rRNA degradation. The detection of trans-splicing in these molecules may indicate broad RNA-joining properties, regardless of the polymerase used for transcription.
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Mayer MG, Floeter-Winter LM. Identification of SL addition trans-splicing acceptor sites in the internal transcribed spacer I region of pre-rRNA in Leishmania (Leishmania) amazonensis. Mem Inst Oswaldo Cruz 2013; 107:1070-2. [PMID: 23295762 DOI: 10.1590/s0074-02762012000800019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 07/28/2012] [Indexed: 11/22/2022] Open
Abstract
Trypanosomatidae is a family of early branching eukaryotes harbouring a distinctive repertoire of gene expression strategies. Functional mature messenger RNA is generated via the trans-splicing and polyadenylation processing of constitutively transcribed polycistronic units. Recently, trans-splicing of pre-small subunit ribosomal RNA in the 5' external transcribed spacer region and of precursor tRNAsec have been described. Here, we used a previously validated semi-nested reverse transcription-polymerase chain reaction strategy to investigate internal transcribed spacer (ITS) I acceptor sites in total RNA from Leishmania (Leishmania) amazonensis. Two distinct spliced leader-containing RNAs were detected indicating that trans-splicing reactions occur at two AG acceptor sites mapped in this ITS region. These data provide further evidence of the wide spectrum of RNA molecules that act as trans-splicing acceptors in trypanosomatids.
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Profiling the venom gland transcriptomes of Costa Rican snakes by 454 pyrosequencing. BMC Genomics 2011; 12:259. [PMID: 21605378 PMCID: PMC3128066 DOI: 10.1186/1471-2164-12-259] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2011] [Accepted: 05/23/2011] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND A long term research goal of venomics, of applied importance for improving current antivenom therapy, but also for drug discovery, is to understand the pharmacological potential of venoms. Individually or combined, proteomic and transcriptomic studies have demonstrated their feasibility to explore in depth the molecular diversity of venoms. In the absence of genome sequence, transcriptomes represent also valuable searchable databases for proteomic projects. RESULTS The venom gland transcriptomes of 8 Costa Rican taxa from 5 genera (Crotalus, Bothrops, Atropoides, Cerrophidion, and Bothriechis) of pitvipers were investigated using high-throughput 454 pyrosequencing. 100,394 out of 330,010 masked reads produced significant hits in the available databases. 5.165,220 nucleotides (8.27%) were masked by RepeatMasker, the vast majority of which corresponding to class I (retroelements) and class II (DNA transposons) mobile elements. BLAST hits included 79,991 matches to entries of the taxonomic suborder Serpentes, of which 62,433 displayed similarity to documented venom proteins. Strong discrepancies between the transcriptome-computed and the proteome-gathered toxin compositions were obvious at first sight. Although the reasons underlaying this discrepancy are elusive, since no clear trend within or between species is apparent, the data indicate that individual mRNA species may be translationally controlled in a species-dependent manner. The minimum number of genes from each toxin family transcribed into the venom gland transcriptome of each species was calculated from multiple alignments of reads matched to a full-length reference sequence of each toxin family. Reads encoding ORF regions of Kazal-type inhibitor-like proteins were uniquely found in Bothriechis schlegelii and B. lateralis transcriptomes, suggesting a genus-specific recruitment event during the early-Middle Miocene. A transcriptome-based cladogram supports the large divergence between A. mexicanus and A. picadoi, and a closer kinship between A. mexicanus and C. godmani. CONCLUSIONS Our comparative next-generation sequencing (NGS) analysis reveals taxon-specific trends governing the formulation of the venom arsenal. Knowledge of the venom proteome provides hints on the translation efficiency of toxin-coding transcripts, contributing thereby to a more accurate interpretation of the transcriptome. The application of NGS to the analysis of snake venom transcriptomes, may represent the tool for opening the door to systems venomics.
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Cassidy-Hanley DM, Cordonnier-Pratt MM, Pratt LH, Devine C, Mozammal Hossain M, Dickerson HW, Clark TG. Transcriptional profiling of stage specific gene expression in the parasitic ciliate Ichthyophthirius multifiliis. Mol Biochem Parasitol 2011; 178:29-39. [PMID: 21524669 DOI: 10.1016/j.molbiopara.2011.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 03/30/2011] [Accepted: 04/06/2011] [Indexed: 01/23/2023]
Abstract
The parasitic ciliate, Ichthyophthirius multifiliis (Ich), is among the most important protozoan pathogens of freshwater fish. Ichthyophthirius cannot be grown in cell culture, and the development of effective prophylactic and therapeutic treatments has been hampered by a lack of information regarding genes involved in virulence, differentiation and growth. To help address this issue, we have generated EST libraries from the two major stages of the parasite life cycle that infect and develop within host tissues. A total of 25,084 ESTs were generated from non-normalized libraries prepared from polyA+ RNA of infective theronts and host-associated trophonts, respectively. Cluster analysis identified 5311 unique transcripts (UniScripts), of which 2091 were contigs and 3220 singletons. Extrapolation of the data based on rates of EST discovery suggests that more than half the expected protein-coding genes of I. multifiliis are represented in this data. BLASTX comparisons against GenBank nr, UniProtKB (SwissProt and TrEMBL), as well as Tetrahymena thermophila, Plasmodium falciparum, and Paramecium tetraurelia protein databases produced 3694 significant (E-value ≤1e(-10)) hits, of which 1178 were annotated using gene ontology (GO) analysis. A high proportion of UniScripts (63%) showed similarity to other ciliate proteins. When combined with expression profiling data, GO ontology analysis of Biological Process, Cellular Component, and Molecular Function revealed interesting differences in gene families expressed in the two stages. Indeed, the most abundant transcripts were highly stage-specific and coincided with the metabolic activities associated with each stage. This work provides an effective genomics resource to further our understanding of Ichthyophthirius biology, and lays the groundwork for the identification of potential drug targets and vaccines candidates for the control of this devastating fish pathogen.
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Affiliation(s)
- Donna M Cassidy-Hanley
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, United States.
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Clayton C, Estevez A. The exosomes of trypanosomes and other protists. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 702:39-49. [PMID: 21713676 DOI: 10.1007/978-1-4419-7841-7_4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The archaeal exosome contains three heterodimeric RNase PH subunits, forming a hexamer with RNase activity; on top sits a trimer of two different SI domain proteins. In animals and yeast, six different, but related subunits form the RNase PH-like core, but these lack enzyme activity; there are three different Si-domain proteins and enzyme activity is provided by the endo/exonuc lease Rrp44 or-mainly in the nuclear exosome-the Rnase D enzyme Rrp6. Trypanosomes diverged from yeast and mammals very early in eukaryotic evolution. The trypanosome exosome is similar in subunit composition to the human exosome, but instead of being an optional component, trypanosome RRP6 is present in the nucleus and cytoplasm and is required for exosome stability. As in human cells and yeast, the trypanosome exosome has been shown to be required for processing and quality control of rRNA and to be involved in mRNA degradation. Electron microscopy results for a Leishmania exosome suggest that RRP6 is located on the side of the RnasePH ring, interacting with several exosome core proteins. Results of a search for exosome subunits in the genomes of widely diverged protists revealed varied exosome complexity; the Giardia exosome may be as simple as that of Archaea.
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Affiliation(s)
- Christine Clayton
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany,
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Gene expression profile of grass shrimp Palaemonetes pugio exposed to chronic hypoxia. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2009; 4:196-208. [DOI: 10.1016/j.cbd.2009.03.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 03/25/2009] [Accepted: 03/27/2009] [Indexed: 12/17/2022]
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Abernathy JW, Xu DH, Li P, Klesius P, Kucuktas H, Liu Z. Transcriptomic profiling of Ichthyophthirius multifiliis reveals polyadenylation of the large subunit ribosomal RNA. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2009; 4:179-86. [PMID: 20403762 DOI: 10.1016/j.cbd.2009.02.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/19/2009] [Accepted: 02/20/2009] [Indexed: 12/11/2022]
Abstract
Polyadenylation of eukaryotic transcripts is usually restricted to mRNA, providing transcripts with stability from degradation by nucleases. Conversely, an RNA degradation pathway can be signaled through poly (A) tailing in prokaryotic, archeal, and organellar biology. Recently polyadenylated transcripts have also been discovered in rRNA in some eukaryotes including humans and yeast. Here we report the discovery of polyadenylated rRNAs in the ciliate teleost parasite Ichthyophthirius multifiliis, an important fish pathogen. Through large-scale analysis of ESTs, a large contig composed of the 28S rRNA with poly (A) tails was identified. Analysis using multiple sequence alignments revealed four potential polyadenylation sites including three internal regions and the 3? end of the rRNA. Further analysis using a polyadenylation test, re-sequencing, and gene-specific PCR using primers flanking the presumed poly (A) sites confirmed the presence of polyadenylated rRNA in this parasite. The functions of polyadenylation of rRNA in this organism are largely unknown at present, but the presence of internal polyadenylation sites, along with the presence of truncated segments of the rRNA, may suggest a role of the polyadenylation in the degradation pathway, a function typical of prokaryotes, archaea, and organelles. These results are in congruence with reports of a similar phenomenon in humans and yeast.
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Affiliation(s)
- Jason W Abernathy
- The Fish Molecular Genetics and Biotechnology Laboratory, Department of Fisheries and Allied Aquacultures and Program of Cell and Molecular Biosciences, Aquatic Genomics Unit, 203 Swingle Hall, Auburn University, AL 36849, USA
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Etheridge RD, Clemens DM, Gershon PD, Aphasizhev R. Identification and characterization of nuclear non-canonical poly(A) polymerases from Trypanosoma brucei. Mol Biochem Parasitol 2008; 164:66-73. [PMID: 19070634 DOI: 10.1016/j.molbiopara.2008.11.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 10/23/2008] [Accepted: 11/11/2008] [Indexed: 01/19/2023]
Abstract
Regulation of nuclear genome expression in Trypanosoma brucei is critical for this protozoan parasite's successful transition between its vertebrate and invertebrate host environments. The canonical eukaryotic circuits such as modulation of transcription initiation, mRNA splicing and polyadenylation appear to be nearly non-existent in T. brucei suggesting that the transcriptome is primarily defined by mRNA turnover. Our previous work has highlighted sequence similarities between terminal RNA uridylyl transferases (TUTases) and non-canonical poly(A) polymerases, which are widely implicated in regulating nuclear, cytoplasmic and organellar RNA decay throughout the eukaryotic lineage. Here, we have continued characterization of TUTase-like proteins in T. brucei and identified two nuclear non-canonical poly(A) polymerases (ncPAPs). The 82kDa TbncPAP1 is essential for viability of procyclic and bloodstream forms of T. brucei. Similar to Trf4/5 proteins from budding yeast, TbncPAP1 requires protein cofactor(s) to exert poly(A) polymerase activity in vitro. The recombinant 54kDa TbncPAP2 showed a PAP activity as an individual polypeptide. Proteomic analysis of the TbncPAP1 interactions demonstrated its association with Mtr4 RNA helicase and several RNA binding proteins, including a potential ortholog of Air1p/2p proteins, which indicates the presence of a stable TRAMP-like complex in trypanosomes. Our findings suggest that TbncPAP1 may be a "quality control" nuclear PAP involved in targeting aberrant or anti-sense transcripts for degradation by the 3'-exosome. Such mechanisms are likely to play a major role in alleviating promiscuity of the transcriptional machinery.
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Affiliation(s)
- Ronald D Etheridge
- Department of Microbiology and Molecular Genetics, School of Medicine, B240 Medical Sciences I, University of California, Irvine, CA 92697, USA
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Houseley J, Tollervey D. The nuclear RNA surveillance machinery: The link between ncRNAs and genome structure in budding yeast? BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2008; 1779:239-46. [DOI: 10.1016/j.bbagrm.2007.12.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 12/18/2007] [Accepted: 12/20/2007] [Indexed: 11/26/2022]
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Doley R, Tram NNB, Reza MA, Kini RM. Unusual accelerated rate of deletions and insertions in toxin genes in the venom glands of the pygmy copperhead (Austrelaps labialis) from Kangaroo island. BMC Evol Biol 2008; 8:70. [PMID: 18307759 PMCID: PMC2287176 DOI: 10.1186/1471-2148-8-70] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Accepted: 02/28/2008] [Indexed: 11/20/2022] Open
Abstract
Background Toxin profiling helps in cataloguing the toxin present in the venom as well as in searching for novel toxins. The former helps in understanding potential pharmacological profile of the venom and evolution of toxins, while the latter contributes to understanding of novel mechanisms of toxicity and provide new research tools or prototypes of therapeutic agents. Results The pygmy copperhead (Austrelaps labialis) is one of the less studied species. In this present study, an attempt has been made to describe the toxin profile of A. labialis from Kangaroo Island using the cDNA library of its venom glands. We sequenced 658 clones which represent the common families of toxin genes present in snake venom. They include (a) putative long-chain and short-chain neurotoxins, (b) phospholipase A2, (c) Kunitz-type protease inhibitor, (d) CRISPs, (e) C-type lectins and (f) Metalloproteases. In addition, we have also identified a novel protein with two Kunitz-type domains in tandem similar to bikunin. Conclusion Interestingly, the cDNA library reveals that most of the toxin families (17 out of 43 toxin genes; ~40%) have truncated transcripts due to insertion or deletion of nucleotides. These truncated products might not be functionally active proteins. However, cellular trancripts from the same venom glands are not affected. This unusual higher rate of deletion and insertion of nucleotide in toxin genes may be responsible for the lower toxicity of A. labialis venom of Kangroo Island and have significant effect on evolution of toxin genes.
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Affiliation(s)
- Robin Doley
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore 117543, Singapore.
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Kumari S, Kumar A, Samant M, Sundar S, Singh N, Dube A. Proteomic approaches for discovery of new targets for vaccine and therapeutics against visceral leishmaniasis. Proteomics Clin Appl 2008; 2:372-86. [PMID: 21136840 DOI: 10.1002/prca.200780017] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Indexed: 11/06/2022]
Abstract
Visceral leishmaniasis (VL) is the most devastating type caused by Leishmania donovani, Leishmania infantum, and Leishmania chagasi. The therapeutic mainstay is still based on the antiquated pentavalent antimonial against which resistance is now increasing. Unfortunately, due to the digenetic life cycle of parasite, there is significant antigenic diversity. There is an urgent need to develop novel drug/vaccine targets against VL for which the primary goal should be to identify and characterize the structural and functional proteins. Proteomics, being widely employed in the study of Leishmania seems to be a suitable strategy as the availability of annotated sequenced genome of Leishmania major has opened the door for dissection of both protein expression/regulation and function. Advances in clinical proteomic technologies have enable to enhance our mechanistic understanding of virulence/pathogenicity/host-pathogen interactions, drug resistance thereby defining novel therapeutic/vaccine targets. Expression proteomics exploits the differential expression of leishmanial proteins as biomarkers for application towards early diagnosis. Further using immunoproteomics efforts were also focused on evaluating responses to define parasite T-cell epitopes as vaccine/diagnostic targets. This review has highlighted some of the relevant developments in the rapidly emerging field of leishmanial proteomics and focus on its future applications in drug and vaccine discovery against VL.
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Affiliation(s)
- Shraddha Kumari
- Division of Parasitology, Central Drug Research Institute, Lucknow, Uttar Pradesh, India
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Pahari S, Mackessy SP, Kini RM. The venom gland transcriptome of the Desert Massasauga rattlesnake (Sistrurus catenatus edwardsii): towards an understanding of venom composition among advanced snakes (Superfamily Colubroidea). BMC Mol Biol 2007; 8:115. [PMID: 18096037 PMCID: PMC2242803 DOI: 10.1186/1471-2199-8-115] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2007] [Accepted: 12/20/2007] [Indexed: 11/14/2022] Open
Abstract
Background Snake venoms are complex mixtures of pharmacologically active proteins and peptides which belong to a small number of superfamilies. Global cataloguing of the venom transcriptome facilitates the identification of new families of toxins as well as helps in understanding the evolution of venom proteomes. Results We have constructed a cDNA library of the venom gland of a threatened rattlesnake (a pitviper), Sistrurus catenatus edwardsii (Desert Massasauga), and sequenced 576 ESTs. Our results demonstrate a high abundance of serine proteinase and metalloproteinase transcripts, indicating that the disruption of hemostasis is a principle mechanism of action of the venom. In addition to the transcripts encoding common venom proteins, we detected two varieties of low abundance unique transcripts in the library; these encode for three-finger toxins and a novel toxin possibly generated from the fusion of two genes. We also observed polyadenylated ribosomal RNAs in the venom gland library, an interesting preliminary obsevation of this unusual phenomenon in a reptilian system. Conclusion The three-finger toxins are characteristic of most elapid venoms but are rare in viperid venoms. We detected several ESTs encoding this group of toxins in this study. We also observed the presence of a transcript encoding a fused protein of two well-characterized toxins (Kunitz/BPTI and Waprins), and this is the first report of this kind of fusion in a snake toxin transcriptome. We propose that these new venom proteins may have ancillary functions for envenomation. The presence of a fused toxin indicates that in addition to gene duplication and accelerated evolution, exon shuffling or transcriptional splicing may also contribute to generating the diversity of toxins and toxin isoforms observed among snake venoms. The detection of low abundance toxins, as observed in this and other studies, indicates a greater compositional similarity of venoms (though potency will differ) among advanced snakes than has been previously recognized.
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Affiliation(s)
- Susanta Pahari
- Center for Post Graduate Studies, Sri Bhagawan Mahaveer Jain College, 18/3, 9th Main, Jayanagar 3rd Block, Bangalore, India.
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Abstract
The yeast putative RNA helicase Mtr4p is implicated in exosome-mediated RNA quality control in the nucleus, interacts with the exosome, and is found in the ‘TRAMP’ complex with a yeast nuclear poly(A) polymerase (Trf4p/Pap2p or Trf5p) and a putative RNA-binding protein, Air1p or Air2p. Depletion of the Trypanosoma brucei MTR4-like protein TbMTR4 caused growth arrest and defects in 5.8S rRNA processing similar to those seen after depletion of the exosome. TbNPAPL, a nuclear protein which is a putative homolog of Trf4p/Pap2p, was required for normal cell growth. Depletion of MTR4 resulted in the accumulation of polyadenylated rRNA precursors, while depletion of TbNPAPL had little effect. These results suggest that polyadenylation-dependent nuclear rRNA quality control is conserved in eukaryotic evolution. In contrast, there was no evidence for a trypanosome TRAMP complex since no stable interactions between TbMTR4 and the exosome, TbNPAPL or RNA-binding proteins were detected.
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Affiliation(s)
- Marina Cristodero
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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Gamboa D, Van Eys G, Victoir K, Torres K, Adaui V, Arevalo J, Dujardin JC. Putative markers of infective life stages in Leishmania (Viannia) braziliensis. Parasitology 2007; 134:1689-98. [PMID: 17897481 DOI: 10.1017/s003118200700306x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Gene expression is known to vary significantly during the Leishmania life-cycle. Its monitoring might allow identification of molecular changes associated with the infective stages (metacyclics and amastigotes) and contribute to the understanding of the complex host-parasite relationships. So far, very few studies have been done on Leishmania (Viannia) braziliensis, one of the most pathogenic species. Such studies require, first of all, reference molecular markers. In the present work, we applied differential display analysis (DD analysis) in order to identify transcripts that might be (i) candidate markers of metacyclics and intracellular amastigotes of L. (V.) braziliensis or (ii) potential controls, i.e. constitutively expressed. In total, 48 DNA fragments gave reliable sequencing data, 29 of them being potential markers of infective stages and 12 potential controls. Eight sequences could be identified with reported genes. Validation of the results of DD analysis was done for 4 genes (2 differentially expressed and 2 controls) by quantitative real-time PCR. The infective insect stage-specific protein (meta 1) was more expressed in metacyclic-enriched preparations. The oligopeptidase b showed a higher expression in amastigotes. Two genes, glucose-6-phosphate dehydrogenase and a serine/threonine protein kinase, were found to be similarly expressed in the different biological samples.
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Affiliation(s)
- D Gamboa
- Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, A.P. 4314, Lima 100, Peru
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Hinas A, Larsson P, Avesson L, Kirsebom LA, Virtanen A, Söderbom F. Identification of the major spliceosomal RNAs in Dictyostelium discoideum reveals developmentally regulated U2 variants and polyadenylated snRNAs. EUKARYOTIC CELL 2006; 5:924-34. [PMID: 16757740 PMCID: PMC1489274 DOI: 10.1128/ec.00065-06] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Most eukaryotic mRNAs depend upon precise removal of introns by the spliceosome, a complex of RNAs and proteins. Splicing of pre-mRNA is known to take place in Dictyostelium discoideum, and we previously isolated the U2 spliceosomal RNA experimentally. In this study, we identified the remaining major spliceosomal RNAs in Dictyostelium by a bioinformatical approach. Expression was verified from 17 small nuclear RNA (snRNA) genes. All these genes are preceded by a putative noncoding RNA gene promoter. Immunoprecipitation showed that snRNAs U1, U2, U4, and U5, but not U6, carry the conserved trimethylated 5' cap structure. A number of divergent U2 species are expressed in Dictyostelium. These RNAs carry the U2 RNA hallmark sequence and structure motifs but have an additional predicted stem-loop structure at the 5' end. Surprisingly, and in contrast to the other spliceosomal RNAs in this study, the new U2 variants were enriched in the cytoplasm and were developmentally regulated. Furthermore, all of the snRNAs could also be detected as polyadenylated species, and polyadenylated U1 RNA was demonstrated to be located in the cytoplasm.
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Affiliation(s)
- Andrea Hinas
- Department of Molecular Biology, Biomedical Center, Swedish University of Agricultural Sciences, Box 590, SE-75124 Uppsala, Sweden
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Abstract
The addition of poly(A)-tails to RNA is a process common to almost all organisms. In eukaryotes, stable poly(A)-tails, important for mRNA stability and translation initiation, are added to the 3′ ends of most nuclear-encoded mRNAs, but not to rRNAs. Contrarily, in prokaryotes and organelles, polyadenylation stimulates RNA degradation. Recently, polyadenylation of nuclear-encoded transcripts in yeast was reported to promote RNA degradation, demonstrating that polyadenylation can play a double-edged role for RNA of nuclear origin. Here we asked whether in human cells ribosomal RNA can undergo polyadenylation. Using both molecular and bioinformatic approaches, we detected non-abundant polyadenylated transcripts of the 18S and 28S rRNAs. Interestingly, many of the post-transcriptionally added tails were composed of heteropolymeric poly(A)-rich sequences containing the other nucleotides in addition to adenosine. These polyadenylated RNA fragments are most likely degradation intermediates, as primer extension (PE) analysis revealed the presence of distal fragmented molecules, some of which matched the polyadenylation sites of the proximal cleavage products revealed by oligo(dT) and circled RT–PCR. These results suggest the presence of a mechanism to degrade ribosomal RNAs in human cells, that possibly initiates with endonucleolytic cleavages and involves the addition of poly(A) or poly(A)-rich tails to truncated transcripts, similar to that which operates in prokaryotes and organelles.
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MESH Headings
- Cell Line, Tumor
- Expressed Sequence Tags
- Humans
- Oligonucleotide Probes
- Poly A/analysis
- Polyadenylation
- RNA Stability
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/metabolism
- RNA, Ribosomal, 18S/analysis
- RNA, Ribosomal, 18S/chemistry
- RNA, Ribosomal, 18S/metabolism
- RNA, Ribosomal, 28S/analysis
- RNA, Ribosomal, 28S/chemistry
- RNA, Ribosomal, 28S/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
| | - David Laufer
- Department of Computer Science, Technion—Israel Institute of TechnologyHaifa 32000, Israel
| | - Dan Geiger
- Department of Computer Science, Technion—Israel Institute of TechnologyHaifa 32000, Israel
| | - Gadi Schuster
- To whom correspondence should be addressed. Tel: 972 4 8293171; Fax: 972 4 8295587;
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