MER121 (DF0000719)

Possible hAT DNA transposon, MER121 subfamily


This element was originally discovered in the human genome and described with a 270 bp long consensus. It was preliminarily classified as a "possible nonautonomous DNA transposon", although none of structural hallmarks of DNA transposons were detected at the time. In 2004, an updated 412-bp version of the MER121 consensus was obtained. In 2006 it was shown [1] that MER121 is a conserved element -- all mammallian genomes contain a few hundred conserved copies of MER121 at orthologous positions. In 2007, the MER121 consensus was improved and characterized by 13-15 bp TIRs, including TA termini. Based on this observation, MER121 was classified as a putative Mariner DNA transposon, characterized by the TA target site duplications. Later, MER121 was reclassified as a member of the hAT superfamily of DNA transposons, based on observation of 8 bp target site duplications around some of full-length copies. It was also noticed that the TIRs of MER121 are similar to TIRs of some hAT transposons from frogs and fish, e.g. hAT-N2_XT. MER121 copies occur at orthologous sites in therian and monotreme genomes, though it has not been detected in chicken or lizard. Note that MER stands for MEdium Reiteration frequency interspersed repeat. As such, MERs as a group are a grab bag of DNA transposons and retrotransposons.


  1. A large family of ancient repeat elements in the human genome is under strong selection.
    Kamal M, Xie X, Lander ES;
    Proc Natl Acad Sci U S A 2006;103:2740-2745 Pubmed


Accession Name Wikipedia
Type DNA Transposon Article
Class Cut and Paste
Superfamily hAT?

Note: Uncertain classification.

Hit Statistics

The model is 401 positions long. The average length of non-redundant hits to the model is 259.8. This table shows the number of hits above score thresholds:

Species Gathering Trusted
non-redundant all hits non-redundant all hits
Mus musculus 655 665 550 555
Homo sapiens 1302 1378 1012 1056

External Database Links

  • Repbase : MER121 [Requires Repbase registration]