Maque, a family of extremely short interspersed repetitive elements: characterization, possible mechanism of transposition, and evolutionary implications

Database analysis revealed a novel family of very short interspersed repeti tive elements named Maque in the African malaria mosquito, Anopheles gambia e. Past mobility of Maque was demonstrated by evidence of its insertion tha t resulted in a target duplication. Approximately 220 copies of Maque were present in the A. gambiae genome. Although only approximately 60 bp long, M aque has the appearance of a distinct transposition unit. Eleven of the 12 Maque elements found in the database were flanked by 9-14 bp direct repeats , indicating that their transposition was relatively recent. Sequence compa rison and phylogenetic analyses suggest that there are at least two subgrou ps within the Maque family, suggesting that they may have been originated f rom more than one source. Five of the 12 Maque elements had at least one ot her repetitive element nearby. Three of the Maque elements were found near genes. However, Maque was not found in the coding regions of genes or in an y of the expressed sequence tags (ESTs), which is consistent with its signi ficantly biased distribution toward A + T rich regions. Several characteris tics of Maque indicate that it is likely a non-autonomous retro-element. Th e evolutionary origin of Maque and the differences between Maque and other known retro-elements including short interspersed repetitive elements (SINE s) are discussed. A hypothesis is proposed in which short sequences contain ing just the reverse transcriptase recognition signal (RTRS) could potentia lly contribute to exon shuffling and the genesis of some primordial SINEs. (C) 2001 Elsevier Science B.V. All rights reserved.