Ingi, a 5.2-kb dispersed sequence element from Trypanosoma brucei that carries half of a smaller mobile element at either end and has homology with mammalian LINEs.

Kimmel, Bruce E.; ole-MoiYoi, Onesmo K.; Young, J. R.

doi:10.1128/mcb.7.4.1465

Cited by 172 publications

(85 citation statements)

References 60 publications

(89 reference statements)

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“…7A). This is consistent with previous reports by others (25) and reflects the highly dispersed genomic organization of the Ingi retroposon family (22). We observed that the decay rate of the majority of the discrete transcripts visible by Northern blotting was similar in ago1 Ϫ/Ϫ and wild-type cells, with the exception of one transcript, indicated by an asterisk in Fig.…”

Section: Ago1 Affects the Accumulation Of Retroposon Transcriptssupporting

confidence: 81%

Argonaute Protein in the Early Divergent Eukaryote Trypanosoma brucei: Control of Small Interfering RNA Accumulation and Retroposon Transcript Abundance

Shi¹,

Djikeng²,

Tschudi³

et al. 2004

Molecular and Cellular Biology

110

140

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Members of the Argonaute protein family have been linked through a combination of genetic and biochemical studies to RNA interference (RNAi) and related phenomena. Here, we describe the characterization of the first Argonaute protein (AGO1) in Trypanosoma brucei, the earliest divergent eukaryote where RNAi has been described so far. AGO1 is predominantly cytoplasmic and is found in a ribonucleoprotein particle with small interfering RNAs (siRNAs), and this particle is present in a soluble form, as well as associated with polyribosomes. A genetic knockout of AGO1 leads to a loss of RNAi, and concomitantly, endogenous retroposonderived siRNAs as well as siRNAs derived from transgenic double-stranded RNA are reduced to almost undetectable levels. Furthermore, AGO1 deficiency leads to an increase in retroposon transcript abundance via mechanisms operating at the transcriptional level and at the RNA stability level. Our results suggest that AGO1 function is required for production and/or stabilization of siRNAs and provide the first evidence for an Argonaute protein being involved in the regulation of retroposon transcript levels.

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Section: Ago1 Affects the Accumulation Of Retroposon Transcriptssupporting

confidence: 81%

Argonaute Protein in the Early Divergent Eukaryote Trypanosoma brucei: Control of Small Interfering RNA Accumulation and Retroposon Transcript Abundance

Shi¹,

Djikeng²,

Tschudi³

et al. 2004

Molecular and Cellular Biology

110

140

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“…6B, all clades were supported with significant bootstrap values (> 50%) using the neighbour-joining method used by the program NJ plot (Perrière and Gouy, 1996). Based on this analysis we found that nimbus (BgI) belongs to clade I (Malik et al, 1999), along with the CiI element of C. intenstinalis (Permanyer, et al, 2003), mosquI from the Aedes aegypti (Tu and Hill 1999), I factor from two different species of Drosophila (Fawcett et al, 1986), and the trypanosome L1 and INGI elements (Kimmel et al, 1987;Martin et al, 1995). Since this is an unrooted tree, the relationship between the major groups cannot be assigned definitively.…”

Section: Phylogenetic Analysis Of the Non-ltr Retrotransposon Nimbus mentioning

confidence: 96%

Nimbus (BgI): An active non-LTR retrotransposon of the Schistosoma mansoni snail host Biomphalaria glabrata

Raghavan

Tettelin²,

Miller

et al. 2007

International Journal for Parasitology

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The freshwater snail Biomphalaria glabrata is closely associated with the transmission of human schistosomiasis. An ecologically sound method has been proposed to control schistosomiasis using genetically modified snails to displace endemic, susceptible ones. To assess the viability of this form of biological control, studies towards understanding the molecular makeup of the snail relative to the presence of endogenous mobile genetic elements are being undertaken since they can be exploited for genetic transformation studies. We previously cloned a 1.95 Kb BamHI fragment in B. glabrata (BGR2) with sequence similarity to the human long interspersed nuclear element (LINE or L1). A contiguous, full-length sequence corresponding to BGR2, hereafter-named nimbus (BgI), has been identified from a B. glabrata bacterial artificial chromosome (BAC) library. Sequence analysis of the 65,764 bp BAC insert contained one full-length, complete nimbus (BgI) element (element I), two full-length elements (elements II and III) containing deletions and flanked by target site duplications and 10 truncated copies. The intact nimbus (BgI) contained two open reading frames (ORFs 1 and 2) encoding the characteristic hallmark domains found in non-long terminal repeat retrotransposons belonging to the I clade; a nucleic acid binding protein in ORF1 and an apurinic/ apyrimidinic endonuclease, reverse transcriptase and RNase H in ORF2. Phylogenetic analysis revealed that nimbus (BgI) is closely related to Drosophila (I factor), mosquito Aedes aegypti (MosquI) and chordate ascidian Ciona intestinalis (CiI) retrotransposons. Nimbus (BgI) represents the first complete mobile element characterized from a mollusk that appears to be transcriptionally active and is widely distributed in snails of the neotropics and the Old World.

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“…) and trypanosomes (Kimmel et al 1987;Teng et al 1995), LTR-retrotransposons have not been found in these lineages. This phylogeny thus suggests that the original LTR-retrotransposon RNH domain was acquired from a non-LTR retrotransposon.…”

Section: Non-ltr Retrotransposons Arose Earlier Than Ltr Retrotranspomentioning

confidence: 99%

Phylogenetic Analysis of Ribonuclease H Domains Suggests a Late, Chimeric Origin of LTR Retrotransposable Elements and Retroviruses

Malik¹,

Eickbush²

2001

Genome Res.

218

200

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We have conducted a phylogenetic analysis of the Ribonuclease HI (RNH) domains present in Eubacteria, Eukarya, all long-term repeat (LTR)-bearing retrotransposons, and several late-branching clades of non-LTR retrotransposons. Analysis of this simple yet highly conserved enzymatic domain from these disparate sources provides surprising insights into the evolution of eukaryotic retrotransposons. First, it indicates that the lineage of elements leading to vertebrate retroviruses acquired a new RNH domain either from non-LTR retrotransposons or from a eukaryotic host genome. The preexisting retroviral RNH domain degenerated to become the tether (connection) domain of the reverse transcriptase (RT)-RNH complex. Second, it indicates that all LTR retrotransposons arose in eukaryotes well after the origin of the non-LTR retrotransposons. Because of the younger age of the LTR retrotransposons, their complex structure, and the absence of any prokaryotic precursors, we propose that the LTR retrotransposons originated as a fusion between a DNA-mediated transposon and a non-LTR retrotransposon. The resulting two-step mechanism of LTR retrotransposition, in which RNA is reverse transcribed away from the chromosomal target site, rather than directly onto the target site, was probably an adaptation to the uncoupling of transcription and translation in eukaryotic cells.

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Ingi, a 5.2-kb dispersed sequence element from Trypanosoma brucei that carries half of a smaller mobile element at either end and has homology with mammalian LINEs.

Cited by 172 publications

References 60 publications

Argonaute Protein in the Early Divergent Eukaryote Trypanosoma brucei: Control of Small Interfering RNA Accumulation and Retroposon Transcript Abundance

Argonaute Protein in the Early Divergent Eukaryote Trypanosoma brucei: Control of Small Interfering RNA Accumulation and Retroposon Transcript Abundance

Nimbus (BgI): An active non-LTR retrotransposon of the Schistosoma mansoni snail host Biomphalaria glabrata

Phylogenetic Analysis of Ribonuclease H Domains Suggests a Late, Chimeric Origin of LTR Retrotransposable Elements and Retroviruses

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