Identification of a non-LTR retrotransposon from the gypsy moth

A family of highly repetitive elements, named LDT1, has been identified in the gypsy moth, Lymantria dispar. The complete element is 5.4 kb in length and lacks long-terminal repeats. The element contains two open reading frames with a significant amino acid sequence similarity to several non-LTR retrotransposons. The first open reading frame contains a region that potentially encodes a polypeptide similar to DNA-binding GAG-like proteins. The second encodes a polypeptide resembling both endonuclease and reverse transcriptase sequences. All members of the LDT1 element family sequenced thus far have poly-A tails or A-rich tails of 12-18 nucleotides in length, but lack a poly-A addition signal in the expected location. The amplification of retrotransposon insertion junction regions in different gypsy moth individuals indicates that polymorphisms exist at some of the insertion sites, suggesting that this element is or was, until recently, capable of transposition.