Characterization of LST-R533: uncovering a novel repetitive element in Leishmania.

We have previously isolated and sequenced a novel repetitive element, now named LST-R533, which is present in four different regions of one extremity of Leishmania major chromosome 20. The repeats are polymorphic in size, ranging from 367 to 533 bp and contain an internal 81 bp sequence with highly conserved segments (14-81 bp long) dispersed throughout the parasite's genome. These sequences were not found in coding regions of any predicted gene in L. major Friedlin genome, but are part of untranslated regions of some Leishmania transcripts. Analysis of the 81 bp sequence revealed significant degrees of identity with retrotransposons described in several other organisms. The presence of the sequence in other species from genus Leishmania was determined by Southern hybridisation and DNA sequencing. This analysis indicated the conservation of the 81-nucleotide element in all the Leishmania species evaluated. No sequences corresponding to LST-R533 or the 81 bp element were found on either Trypanosoma brucei or Trypanosoma cruzi databanks.