TAS, A RETROTRANSPOSON FROM THE PARASITIC NEMATODE ASCARIS-LUMBRICOIDES

The cloned retrotransposon Tas OE3 from the genome of the parasitic ne matode Ascaris lumbricoides was completely sequenced. The element is f lanked by long terminal repeats (LTR) and contains three distinct regi ons encoding putative proteins typical for retroid elements. The first region, ORF1, encodes a putative Gag protein including a 'Leu zipper' , a nucleic acid binding motif, as well as an aspartic protease domain . The second region contains an incomplete ORF (ORF2) with sequence si milarities to known retroviral reverse transcriptases (RT), ribonuclea ses H and integrases. A third ORF, which is located adjacent to the 3' LTR, might encode an env-like protein. Based on amino-acid sequence a nalysis of the RT domain, Tas falls into a new subgroup of LTR-contain ing retrotransposons.