Tec3, a New Developmentally Eliminated DNA Element in
            <i>Euplotes crassus</i>

Jacobs, Mary Ellen; Sánchez-Blanco, Adolfo; Katz, Laura A.; Klobutcher, Lawrence A.

doi:10.1128/ec.2.1.103-114.2003

Cited by 18 publications

(14 citation statements)

References 55 publications

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“…The two bestcharacterized Tec elements, Tec1 and Tec2, are highly abundant (~12 000 copies per genome), are flanked by long terminal inverted repeats (TIRs), and in addition to the tyrosine recombinase, they encode a typical Tc1/mariner DDE-type transposase (Doak et al, 2003). Tec3 is less well characterized, but is also known to have long TIRs (Jacobs et al, 2003). In contrast, cryptons appear at lower copy numbers, they do not have TIRs, do not encode a DDE-type transposase, and they contain some protein-coding domains that are not found in Tec elements.…”

Section: Discussionmentioning

confidence: 99%

“…6). As has been noted earlier (Esposito & Scocca, 1997;Goodwin & Poulter, 2001a;Jacobs et al, 2003), phylogenetic analyses of tyrosine recombinases are hindered by the high level of sequence diversity within the group. This usually means that the nature of the more distant relationships within the group cannot be resolved with certainty using current techniques.…”

Section: Evolutionary Analysesmentioning

confidence: 99%

“…D Goodwin & R. T. M. Poulter, unpublished). In addition, several eukaryotic DNA transposons which bear tyrosine recombinase genes have very recently been described (Doak et al, 2003;Jacobs et al, 2003). These elements were found in the ciliate Euplotes crassus, and like most other DNA transposons they are flanked by long terminal inverted repeats.…”

Section: Introductionmentioning

confidence: 99%

“…Tec1 and Tec2 (Doak et al, 2003) each encode a Tc1/mariner-like DDE-type transposase as well as the tyrosine recombinase, and it is possible that the recombinase serves as a resolvase rather than as a transposase. The full complement of coding regions in Tec3 (Jacobs et al, 2003) is not yet known.…”

Section: Introductionmentioning

confidence: 99%

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Cryptons: a group of tyrosine-recombinase-encoding DNA transposons from pathogenic fungi

2003

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A new group of transposable elements, which the authors have named cryptons, was detected in several pathogenic fungi, including the basidiomycete Cryptococcus neoformans, and the ascomycetes Coccidioides posadasii and Histoplasma capsulatum. These elements are unlike any previously described transposons. An archetypal member of the group, crypton Cn1, is 4 kb in length and is present at a low but variable copy number in a variety of C. neoformans strains. It displays interstrain variations in its insertion sites, suggesting recent mobility. The internal region contains a long gene, interrupted by several introns. The product of this gene contains a putative tyrosine recombinase near its middle, and a region similar in sequence to the DNA-binding domains of several fungal transcription factors near its C-terminus. The element contains no long repeat sequences, but is bordered by short direct repeats which may have been produced by its insertion into the host genome by recombination. Many of the structural features of crypton Cn1 are conserved in the other known cryptons, suggesting that these elements represent the functional forms. The presence of cryptons in ascomycetes and basidiomycetes suggests that this is an ancient group of elements (>400 million years old). Sequence comparisons suggest that cryptons may be related to the DIRS1 and Ngaro1 groups of tyrosine-recombinaseencoding retrotransposons.

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Section: Discussionmentioning

confidence: 99%

Section: Evolutionary Analysesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cryptons: a group of tyrosine-recombinase-encoding DNA transposons from pathogenic fungi

2003

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“…DNA-based transposons have been characterized in the micronuclear genome of several spirotrichous ciliates (14,(28)(29)(30). In T. thermophila, several transposon-like families have been identified.…”

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confidence: 99%

A Non-Long Terminal Repeat Retrotransposon Family Is Restricted to the Germ Line Micronucleus of the Ciliated Protozoan Tetrahymena thermophila

et al. 2004

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The ciliated protozoan Tetrahymena thermophila undergoes extensive programmed DNA rearrangements during the development of a somatic macronucleus from the germ line micronucleus in its sexual cycle. To investigate the relationship between programmed DNA rearrangements and transposable elements, we identified several members of a family of non-long terminal repeat (LTR) retrotransposons (retroposons) in T. thermophila, the first characterized in the ciliated protozoa. This multiple-copy retrotransposon family is restricted to the micronucleus of T. thermophila. The REP (Tetrahymena non-LTR retroposon) elements encode an ORF2 typical of non-LTR elements that contains apurinic/apyrimidinic endonuclease (APE) and reverse transcriptase (RT) domains. Phylogenetic analysis of the RT and APE domains indicates that the element forms a deep-branching clade within the non-LTR retrotransposon family. Northern analysis with a probe to the conserved RT domain indicates that transcripts from the element are small and heterogeneous in length during early macronuclear development. The presence of a repeated transposable element in the genome is consistent with the model that programmed DNA deletion in T. thermophila evolved as a method of eliminating deleterious transposons from the somatic macronucleus.Developmentally programmed DNA rearrangements occur in a wide variety of organisms (reviewed in reference 5). Functions such as altering gene dosage or directly regulating gene expression have been assigned to many but not all examples of programmed DNA rearrangements. A clinically important example of a programmed DNA rearrangement is V(D)J recombination (2). In addition, a variety of mammalian parasites use programmed DNA rearrangements to vary their surface antigens to avoid host immune response (4). The function of other programmed DNA rearrangements is not as clear. The extensive genome rearrangements that occur during nuclear development in the ciliated protozoa provide an example of programmed DNA rearrangements with poorly understood function.Like all ciliated protozoa, the oligohymenopheran Tetrahymena thermophila displays nuclear dimorphism with a mostly transcriptionally silent diploid germ line nucleus (micronucleus) and a polyploid and transcriptionally active somatic nucleus (macronucleus) within the same cell. The macronucleus develops from a mitotic product of the micronucleus during conjugation. When two cells of different mating types conjugate, the micronucleus in each divides meiotically and mitotically to generate a haploid gametic nucleus that is reciprocally exchanged and fuses with that of its partner to form a zygotic nucleus. This zygotic nucleus divides and from one of the products develops a new macronucleus, while the old macronucleus is concurrently degraded. In T. thermophila, macronuclear development involves extensive programmed DNA rearrangements, including chromosome fragmentation, DNA amplification, and site-specific interstitial DNA deletion (12). Interstitial DNA deletion is responsible for t...

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Genomes on the Edge: Programmed Genome Instability in Ciliates

Bracht

Fang

Goldman

et al. 2013

Cell

102

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Ciliates are an ancient and diverse group of microbial eukaryotes that have emerged as powerful models for RNA-mediated epigenetic inheritance. They possess extensive sets of both tiny and long noncoding RNAs that, together with a suite of proteins that includes transposases, orchestrate a broad cascade of genome rearrangements during somatic nuclear development. This Review emphasizes three important themes: the remarkable role of RNA in shaping genome structure, recent discoveries that unify many deeply diverged ciliate genetic systems, and a surprising evolutionary “sign change” in the role of small RNAs between major species groups.

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Tec3, a New Developmentally Eliminated DNA Element in Euplotes crassus

Cited by 18 publications

References 55 publications

Cryptons: a group of tyrosine-recombinase-encoding DNA transposons from pathogenic fungi

Cryptons: a group of tyrosine-recombinase-encoding DNA transposons from pathogenic fungi

A Non-Long Terminal Repeat Retrotransposon Family Is Restricted to the Germ Line Micronucleus of the Ciliated Protozoan Tetrahymena thermophila

Genomes on the Edge: Programmed Genome Instability in Ciliates

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