|Name||HeT-A element||FlyBase ID||FBte0000143|
|Feature type||natural transposable element|
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|Sequences & Components|
|Complete element (bp)||
|Terminal repeat (bp)|
|Sequence Ontology (SO)|
|Insertions & Copy Number|
3 in euchromatin of Release 3 genome annotation, of which zero are full length.
|Target Site Duplication|
|Curated drosophilid orthologs|
HeT-A and TART-element, previously considered to be closely related, have very different transcriptional characteristics. Additionally, features of TART-element sequence organisation resemble those of a subclass of non-LTR elements characterized by unequal terminal repeats. The distinctive transcription patterns of HeT-A and TART-element are conserved in D.yakuba.
HeT-A sequences have been found in the centric heterochromatin of chromosome 3.
The HeT-A promoter is at the 3' end of the element and directs transcription of the HeT-A element immediately downstream in the tandem array in which they are found. The HeT-A element appears to be an evolutionary intermediate between LTR and non-LTR retrotransposons. Considering two HeT-A elements in tandem array, the promoter-containing 3' end of the upstream element is identical to the promoter-containing 3' end of the downstream element, and this "extended element" is structurally and functionally equivalent to an LTR retrotransposon. The promoter-containing 3' end of the upstream element acts as a surrogate for the 5' LTR characteristic of the LTR retrotransposon, although it is actually part of the flanking element. The HeT-A element does not encode its own reverse transcriptase.
Comparison of integrase/transposase domains to new elements containing the DDE signature.
HeT-A promoter activity is located in the 3' end of the element. In HeT-A arrays the 3' sequence of one element directs transcription of its downstream neighbour.
HeT-A element and TART-element may be evolutionarily related to telomerase, in both cases an enzyme extends the end of a chromosome by adding DNA copied from an RNA template.
A HeT-A element has been cloned and sequenced. The unit length of the HeT-A element is approximately 6kb.
The HeT-A element is approximately 6kb in length. It can be divided into three regions; a protein coding region composed of two overlapping reading frames, a 5' non-coding region and a 3' non-coding region (which makes up approximately half the HeT-A element).
Analysis of HeT-A transcripts suggests that HeT-A elements transposase by means of a polyadenylated RNA intermediate and that each element joins to the chromosome end by means of the poly(A) tail of the RNA.
The genomic organization (oligo(A) tails facing proximally at chromosome ends) and sequence analysis of 29 different HeT-A fragments supports the model of telomere elongation by transposition of HeT-A elements.
HeT-A sequences are never found in the euchromatin. Y associated HeT-A clusters have significantly different structures than telomeric clusters, and may arise by different transposition mechanisms.
A transposon family of non-long terminal repeat retrotransposons found at the telomere. HeT-A elements transpose to broken chromosome ends. Evidence suggests that they can also transpose to natural chromosome ends.
HeT-A is a transposable element that heals broken chromosomes: it may have a structural role in telomere organization or maintenance.
Transposition of HeT-A onto broken chromosome ends is implicated in chromosome healing. Ends of X chromosomes with new HeT-A additions receded at the same rate as broken ends before HeT-A elements attached. Approximately 1% of chromosomes per generation aquired new HeT-A sequences of an average of 6kb at their ends, and the rate of addition of new material per generation matches the observed rate of loss caused by incomplete replication at the ends of the DNA molecule. Transposition of HeT-A onto broken chromosome ends is implicated in chromosome healing. Ends of X chromosomes with new HeT-A additions receded at the same rate as broken ends before HeT-A elements attached. Approximately 1% of chromosomes per generation aquired new HeT-A sequences of an average of 6kb at their ends, and the rate of addition of new material per generation matches the observed rate of loss caused by incomplete replication at the ends of the DNA molecule.
Sequence of a HeT-A element includes two overlapping open reading frames that are one nucleotide out of frame with respect to each other. The longer ORF contains Cys-His motifs strongly resembling nucleic acid binding domains of gag-like proteins and the overall organisation is reminiscent of LINE elements.
HeT-As is transcribed and are conserved in the D.melanogaster species subgroup. It may play a role in the structure and/or function of telomeres.
construct_comment: Associated with telomeres.
The distribution of different subfragments of HeT-A DNA throughout the genome has been studied.
|Synonyms & Secondary IDs ( 15 )|
(Kern and Begum, 2008, Zhang et al., 2011, Maxwell et al., 2006, Raffa et al., 2005, Klattenhoff et al., 2007, Zaratiegui, 2007, Vagin et al., 2006, Villasante et al., 2007, Pane et al., 2011, Klenov et al., 2007, George et al., 2006, Lim and Kai, 2007, Gunawardane et al., 2007, Traverse et al., 2010, Shpiz et al., 2011, Shpiz et al., 2007, Torok et al., 2007, Brennecke et al., 2007, Savitsky et al., 2002, Kalmykova et al., 2008, Frydrychova et al., 2008, Shpiz et al., 2008, Yin and Lin, 2007, Nardon et al., 2003, Horwich et al., 2007, Debaryshe and Pardue, 2011, Frydrychova et al., 2007, Kawamura et al., 2008, Deloger et al., 2009, Frydrychova et al., 2008, Chen et al., 2007, Anand and Kai, 2012, Cenci et al., 2003, Mason et al., 2003, Shpiz et al., 2009, Lim et al., 2009, Li et al., 2009, Phalke et al., 2009, Oikemus et al., 2006, Gao et al., 2010, Fuller et al., 2010, Gou et al., 2010, Rozhkov et al., 2010, Handler et al., 2011, George et al., 2010, Khurana et al., 2010, Tan et al., 2012, Wang and Elgin, 2011, Sienski et al., 2012, Takács et al., 2012, Klenov et al., 2011, Sreesankar et al., 2012, Olivieri et al., 2012)
(Purdy and Su, 2004, Fedic et al., 2004, Kapitonov and Jurka, 2003, Leonardo and Nuzhdin, 2002, Bartolome et al., 2002, Bestor, 1999, Miller et al., 1999, Siriaco et al., 1999, Georgiev et al., 1999, Dimitri and Junakovic, 1999, Abdulla, 1997, Capy et al., 1997, Anonymous, 1994, Saito et al., 2006, Pane et al., 2007, Gvozdev et al., 2005, Ghildiyal et al., 2008, Pane et al., 2007, Doheny et al., 2008, Chen et al., 2007, Navarro et al., 2009, Klattenhoff et al., 2009, Bergman et al., 2006, Patil and Kai, 2010, Preall et al., 2012)
telomeric HeT-A element
|Secondary FlyBase IDs|
|References ( 225 )|
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|Recent research papers ( 15 )|
|Recent reviews (0)|
|All reviews listed in FlyBase were published before 2011|