@article {49642, title = {Members of a large retroposon family are determinants of post-transcriptional gene expression in Leishmania.}, journal = {PLoS Pathog}, volume = {3}, year = {2007}, month = {2007 Sep 7}, pages = {1291-307}, abstract = {

Trypanosomatids are unicellular protists that include the human pathogens Leishmania spp. (leishmaniasis), Trypanosoma brucei (sleeping sickness), and Trypanosoma cruzi (Chagas disease). Analysis of their recently completed genomes confirmed the presence of non-long-terminal repeat retrotransposons, also called retroposons. Using the 79-bp signature sequence common to all trypanosomatid retroposons as bait, we identified in the Leishmania major genome two new large families of small elements--LmSIDER1 (785 copies) and LmSIDER2 (1,073 copies)--that fulfill all the characteristics of extinct trypanosomatid retroposons. LmSIDERs are approximately 70 times more abundant in L. major compared to T. brucei and are found almost exclusively within the 3{\textquoteright}-untranslated regions (3{\textquoteright}UTRs) of L. major mRNAs. We provide experimental evidence that LmSIDER2 act as mRNA instability elements and that LmSIDER2-containing mRNAs are generally expressed at lower levels compared to the non-LmSIDER2 mRNAs. The considerable expansion of LmSIDERs within 3{\textquoteright}UTRs in an organism lacking transcriptional control and their role in regulating mRNA stability indicate that Leishmania have probably recycled these short retroposons to globally modulate the expression of a number of genes. To our knowledge, this is the first example in eukaryotes of the domestication and expansion of a family of mobile elements that have evolved to fulfill a critical cellular function.

}, keywords = {3{\textquoteright} Untranslated Regions, Animals, Base Sequence, Biological Evolution, Down-Regulation, Gene Expression Regulation, Genome, Protozoan, Leishmania, Leishmania major, Molecular Sequence Data, Retroelements, RNA, Messenger, sequence alignment, Trypanosoma brucei brucei, Trypanosoma cruzi}, issn = {1553-7374}, doi = {10.1371/journal.ppat.0030136}, author = {Bringaud, Frederic and M{\"u}ller, Michaela and Cerqueira, Gustavo Coutinho and Smith, Martin and Rochette, Annie and el-Sayed, Najib M A and Papadopoulou, Barbara and Ghedin, Elodie} } @article {49639, title = {The Trypanosoma cruzi L1Tc and NARTc non-LTR retrotransposons show relative site specificity for insertion.}, journal = {Mol Biol Evol}, volume = {23}, year = {2006}, month = {2006 Feb}, pages = {411-20}, abstract = {

The trypanosomatid protozoan Trypanosoma cruzi contains long autonomous (L1Tc) and short nonautonomous (NARTc) non-long terminal repeat retrotransposons. NARTc (0.25 kb) probably derived from L1Tc (4.9 kb) by 3{\textquoteright}-deletion. It has been proposed that their apparent random distribution in the genome is related to the L1Tc-encoded apurinic/apyrimidinic endonuclease (APE) activity, which repairs modified residues. To address this question we used the T. cruzi (CL-Brener strain) genome data to analyze the distribution of all the L1Tc/NARTc elements present in contigs larger than 10 kb. This data set, which represents 0.91x sequence coverage of the haploid nuclear genome ( approximately 55 Mb), contains 419 elements, including 112 full-length L1Tc elements (14 of which are potentially functional) and 84 full-length NARTc. Approximately half of the full-length elements are flanked by a target site duplication, most of them (87\%) are 12 bp long. Statistical analyses of sequences flanking the full-length elements show the same highly conserved pattern upstream of both the L1Tc and NARTc retrotransposons. The two most conserved residues are a guanine and an adenine, which flank the site where first-strand cleavage is performed by the element-encoded endonuclease activity. This analysis clearly indicates that the L1Tc and NARTc elements display relative site specificity for insertion, which suggests that the APE activity is not responsible for first-strand cleavage of the target site.

}, keywords = {Animals, DNA, Protozoan, DNA-(Apurinic or Apyrimidinic Site) Lyase, Mutagenesis, Insertional, Retroelements, Sequence Deletion, Trypanosoma cruzi}, issn = {0737-4038}, doi = {10.1093/molbev/msj046}, author = {Bringaud, Frederic and Bartholomeu, Daniella C and Blandin, Ga{\"e}lle and Delcher, Arthur and Baltz, Th{\'e}o and el-Sayed, Najib M A and Ghedin, Elodie} } @article {49636, title = {Telomere and subtelomere of Trypanosoma cruzi chromosomes are enriched in (pseudo)genes of retrotransposon hot spot and trans-sialidase-like gene families: the origins of T. cruzi telomeres.}, journal = {Gene}, volume = {346}, year = {2005}, month = {2005 Feb 14}, pages = {153-61}, abstract = {

Here, we sequenced two large telomeric regions obtained from the pathogen protozoan Trypanosoma cruzi. These sequences, together with in silico assembled contigs, allowed us to establish the general features of telomeres and subtelomeres of this parasite. Our findings can be summarized as follows: We confirmed the presence of two types of telomeric ends; subtelomeric regions appeared to be enriched in (pseudo)genes of RHS (retrotransposon hot spot), TS (trans-sialidase)-like proteins, and putative surface protein DGF-1 (dispersed gene family-1). Sequence analysis of the ts-like genes located at the telomeres suggested that T. cruzi chromosomal ends could have been the site for generation of new gp85 variants, an important adhesin molecule involved in the invasion of mammalian cells by T. cruzi. Finally, a mechanism for generation of T. cruzi telomere by chromosome breakage and telomere healing is proposed.

}, keywords = {Amino Acid Sequence, Animals, Base Sequence, Chromosomes, Chromosomes, Artificial, Bacterial, DNA, Protozoan, Genes, Protozoan, Glycoproteins, Molecular Sequence Data, Multigene Family, Neuraminidase, Pseudogenes, Retroelements, Sequence Homology, Amino Acid, Sequence Homology, Nucleic Acid, Telomere, Trypanosoma cruzi}, issn = {0378-1119}, doi = {10.1016/j.gene.2004.10.014}, author = {Kim, Dong and Chiurillo, Miguel Angel and El-Sayed, Najib and Jones, Kristin and Santos, M{\'a}rcia R M and Porcile, Patricio E and Andersson, Bj{\"o}rn and Myler, Peter and da Silveira, Jose Franco and Ram{\'\i}rez, Jos{\'e} Luis} } @article {49635, title = {Gene synteny and evolution of genome architecture in trypanosomatids.}, journal = {Mol Biochem Parasitol}, volume = {134}, year = {2004}, month = {2004 Apr}, pages = {183-91}, abstract = {

The trypanosomatid protozoa Trypanosoma brucei, Trypanosoma cruzi and Leishmania major are related human pathogens that cause markedly distinct diseases. Using information from genome sequencing projects currently underway, we have compared the sequences of large chromosomal fragments from each species. Despite high levels of divergence at the sequence level, these three species exhibit a striking conservation of gene order, suggesting that selection has maintained gene order among the trypanosomatids over hundreds of millions of years of evolution. The few sites of genome rearrangement between these species are marked by the presence of retrotransposon-like elements, suggesting that retrotransposons may have played an important role in shaping trypanosomatid genome organization. A degenerate retroelement was identified in L. major by examining the regions near breakage points of the synteny. This is the first such element found in L. major suggesting that retroelements were found in the common ancestor of all three species.

}, keywords = {Animals, Computational Biology, Evolution, Molecular, Gene Order, Genome, Protozoan, Genomics, Leishmania major, Multigene Family, Recombination, Genetic, Retroelements, Selection, Genetic, Synteny, Trypanosoma brucei brucei, Trypanosoma cruzi, Trypanosomatina}, issn = {0166-6851}, doi = {10.1016/j.molbiopara.2003.11.012}, author = {Ghedin, Elodie and Bringaud, Frederic and Peterson, Jeremy and Myler, Peter and Berriman, Matthew and Ivens, Alasdair and Andersson, Bj{\"o}rn and Bontempi, Esteban and Eisen, Jonathan and Angiuoli, Sam and Wanless, David and Von Arx, Anna and Murphy, Lee and Lennard, Nicola and Salzberg, Steven and Adams, Mark D and White, Owen and Hall, Neil and Stuart, Kenneth and Fraser, Claire M and el-Sayed, Najib M A} } @article {49634, title = {The ingi and RIME non-LTR retrotransposons are not randomly distributed in the genome of Trypanosoma brucei.}, journal = {Mol Biol Evol}, volume = {21}, year = {2004}, month = {2004 Mar}, pages = {520-8}, abstract = {

The ingi (long and autonomous) and RIME (short and nonautonomous) non--long-terminal repeat retrotransposons are the most abundant mobile elements characterized to date in the genome of the African trypanosome Trypanosoma brucei. These retrotransposons were thought to be randomly distributed, but a detailed and comprehensive analysis of their genomic distribution had not been performed until now. To address this question, we analyzed the ingi/RIME sequences and flanking sequences from the ongoing T. brucei genome sequencing project (TREU927/4 strain). Among the 81 ingi/RIME elements analyzed, 60\% are complete, and 7\% of the ingi elements (approximately 15 copies per haploid genome) appear to encode for their own transposition. The size of the direct repeat flanking the ingi/RIME retrotransposons is conserved (i.e., 12-bp), and a strong 11-bp consensus pattern precedes the 5{\textquoteright}-direct repeat. The presence of a consensus pattern upstream of the retroelements was confirmed by the analysis of the base occurrence in 294 GSS containing 5{\textquoteright}-adjacent ingi/RIME sequences. The conserved sequence is present upstream of ingis and RIMEs, suggesting that ingi-encoded enzymatic activities are used for retrotransposition of RIMEs, which are short nonautonomous retroelements. In conclusion, the ingi and RIME retroelements are not randomly distributed in the genome of T. brucei and are preceded by a conserved sequence, which may be the recognition site of the ingi-encoded endonuclease.

}, keywords = {Amino Acid Sequence, Animals, Base Sequence, Consensus Sequence, Genome, Protozoan, Molecular Sequence Data, Retroelements, Sequence Analysis, Trypanosoma brucei brucei}, issn = {0737-4038}, doi = {10.1093/molbev/msh045}, author = {Bringaud, Frederic and Biteau, Nicolas and Zuiderwijk, Eduard and Berriman, Matthew and El-Sayed, Najib M and Ghedin, Elodie and Melville, Sara E and Hall, Neil and Baltz, Th{\'e}o} } @article {49630, title = {Identification of non-autonomous non-LTR retrotransposons in the genome of Trypanosoma cruzi.}, journal = {Mol Biochem Parasitol}, volume = {124}, year = {2002}, month = {2002 Sep-Oct}, pages = {73-8}, abstract = {

As observed for most eukaryotic cells, trypanosomatids contains non-LTR retrotransposons randomly inserted in the nuclear genome. Autonomous retroelements which, code for their own transposition, have been characterized in Trypanosoma brucei (ingi) and Trypanosoma cruzi (L1Tc), whereas non-autonomous retroelements have only been characterized in T. brucei (RIME). Here, we have characterized in the genome of Trypanosoma cruzi four complete copies of a non-autonomous non-LTR retrotransposon, called NARTc. This 0.26 kb NARTc element has the characteristics of non-LTR retrotransposons: the presence a poly(dA) tail and of a short flanking duplicated motif. Analysis of the Genome Survey Sequence databases indicated that the Trypanosoma cruzi haploid genome contains about 140 NARTc copies and about twice as many L1Tc copies. Interestingly, the NARTc and L1Tc retroelements share, with the Trypanosoma brucei ingi and RIME retrotransposons, a common sequence (the first 45 bp with 91\% identity), whereas the remaining sequences are very divergent. This suggests that these four trypanosome non-LTR retrotransposons were derived from the same common ancester and the sequence of their 5{\textquoteright}-extremity may have a functional role. In addition, the genome of Leishmania major contains the same conserved motif present in the trypanosome retroelements, whicle no transposable elements have been detected so far in Leishmania sp.

}, keywords = {Animals, Base Sequence, Computational Biology, Genome, Protozoan, Long Interspersed Nucleotide Elements, Molecular Sequence Data, Retroelements, Short Interspersed Nucleotide Elements, Trypanosoma cruzi}, issn = {0166-6851}, author = {Bringaud, Frederic and Garc{\'\i}a-P{\'e}rez, Jos{\'e} Luis and Heras, Sara R and Ghedin, Elodie and El-Sayed, Najib M and Andersson, Bj{\"o}rn and Baltz, Th{\'e}o and Lopez, Manuel C} } @article {49631, title = {A new, expressed multigene family containing a hot spot for insertion of retroelements is associated with polymorphic subtelomeric regions of Trypanosoma brucei.}, journal = {Eukaryot Cell}, volume = {1}, year = {2002}, month = {2002 Feb}, pages = {137-51}, abstract = {

We describe a novel gene family that forms clusters in subtelomeric regions of Trypanosoma brucei chromosomes and partially accounts for the observed clustering of retrotransposons. The ingi and ribosomal inserted mobile element (RIME) non-LTR retrotransposons share 250 bp at both extremities and are the most abundant putatively mobile elements, with about 500 copies per haploid genome. From cDNA clones and subsequently in the T. brucei genomic DNA databases, we identified 52 homologous gene and pseudogene sequences, 16 of which contain a RIME and/or ingi retrotransposon inserted at exactly the same relative position. Here these genes are called the RHS family, for retrotransposon hot spot. Comparison of the protein sequences encoded by RHS genes (21 copies) and pseudogenes (24 copies) revealed a conserved central region containing an ATP/GTP-binding motif and the RIME/ingi insertion site. The RHS proteins share between 13 and 96\% identity, and six subfamilies, RHS1 to RHS6, can be defined on the basis of their divergent C-terminal domains. Immunofluorescence and Western blot analyses using RHS subfamily-specific immune sera show that RHS proteins are constitutively expressed and occur mainly in the nucleus. Analysis of Genome Survey Sequence databases indicated that the Trypanosoma brucei diploid genome contains about 280 RHS (pseudo)genes. Among the 52 identified RHS (pseudo)genes, 48 copies are in three RHS clusters located in subtelomeric regions of chromosomes Ia and II and adjacent to the active bloodstream form expression site in T. brucei strain TREU927/4 GUTat10.1. RHS genes comprise the remaining sequence of the size-polymorphic "repetitive region" described for T. brucei chromosome I, and a homologous gene family is present in the Trypanosoma cruzi genome.

}, keywords = {Amino Acid Sequence, Animals, Base Sequence, Cloning, Molecular, DNA Primers, DNA, Protozoan, Escherichia coli, Genes, Protozoan, Molecular Sequence Data, Multigene Family, Mutagenesis, Insertional, Phylogeny, Polymorphism, Genetic, Protozoan Proteins, Pseudogenes, Retroelements, sequence alignment, Sequence Homology, Amino Acid, Telomere, Trypanosoma brucei brucei, Trypanosoma cruzi}, issn = {1535-9778}, author = {Bringaud, Frederic and Biteau, Nicolas and Melville, Sara E and Hez, St{\'e}phanie and El-Sayed, Najib M and Leech, Vanessa and Berriman, Matthew and Hall, Neil and Donelson, John E and Baltz, Th{\'e}o} } @article {49701, title = {Species-specific signals for the splicing of a short Drosophila intron in vitro.}, journal = {Mol Cell Biol}, volume = {13}, year = {1993}, month = {1993 Feb}, pages = {1104-18}, abstract = {

The effects of branchpoint sequence, the pyrimidine stretch, and intron size on the splicing efficiency of the Drosophila white gene second intron were examined in nuclear extracts from Drosophila and human cells. This 74-nucleotide intron is typical of many Drosophila introns in that it lacks a significant pyrimidine stretch and is below the minimum size required for splicing in human nuclear extracts. Alteration of sequences of adjacent to the 3{\textquoteright} splice site to create a pyrimidine stretch was necessary for splicing in human, but not Drosophila, extracts. Increasing the size of this intron with insertions between the 5{\textquoteright} splice site and the branchpoint greatly reduced the efficiency of splicing of introns longer than 79 nucleotides in Drosophila extracts but had an opposite effect in human extracts, in which introns longer than 78 nucleotides were spliced with much greater efficiency. The white-apricot copia insertion is immediately adjacent to the branchpoint normally used in the splicing of this intron, and a copia long terminal repeat insertion prevents splicing in Drosophila, but not human, extracts. However, a consensus branchpoint does not restore the splicing of introns containing the copia long terminal repeat, and alteration of the wild-type branchpoint sequence alone does not eliminate splicing. These results demonstrate species specificity of splicing signals, particularly pyrimidine stretch and size requirements, and raise the possibility that variant mechanisms not found in mammals may operate in the splicing of small introns in Drosophila and possibly other species.

}, keywords = {Animals, Base Sequence, Cell Nucleus, Consensus Sequence, DNA, DNA Transposable Elements, Drosophila, Drosophila Proteins, Electrophoresis, Polyacrylamide Gel, HeLa Cells, HUMANS, Introns, Molecular Sequence Data, Mutation, Peptide Hydrolases, Proteins, Regulatory Sequences, Nucleic Acid, Retroelements, RNA Splicing, Species Specificity}, issn = {0270-7306}, author = {Guo, M and Lo, P C and Mount, S M} }