Characterization of a non-long terminal repeat retrotransposon cDNA (L1Tc) from Trypanosoma cruzi: homology of the first ORF with the ape family of DNA repair enzymes.

In the present paper we describe the characterization of a Trypanosoma cruzi cDNA (L1Tc) corresponding to a transcript from a new long terminal repeat (LTR) retrotransposon. This element is present in a high-copy number, and is found dispersed throughout the T. cruzi genome. Northern analysis shows an abundant expression of L1Tc-related sequences with a major band of about 5 kb. The transcript has at its 3' end a fragment of a highly repetitive DNA sequence (E12A), at its 5' end a ribosomal mobile element-like sequence and three putative open reading frames (ORF) in different frames. The ORF2 codes for a protein which has significant homology with the retrotranscriptase-related sequences from non-LTR retrotransposons containing the seven domains present in all the retrotranscriptase and retrotranscriptase-related proteins. The ORF3 codes for a gag-like protein showing unusual cysteine motifs present in all non-LTR trypanosomatid elements, similar to the C2H2 zinc finger family of transcription factors. Interestingly, ORF1 codes for a protein with significant homology to the major human AP endonuclease protein, and maintains in similar positions most of the amino acid domains described for all the Ape family of proteins. The presence of Ape-related sequences, described for the first time in a non-LTR retrotransposon (L1Tc), may have functional relevance for these types of elements.