El copyright pertenece a Oxford University Press. La publicación original está disponible en http://nar.oxfordjournals.org/?code=nar&.cgifields=codeL1Tc is the best represented autonomous LINE of the Trypanosoma cruzi genome, throughout which several functional copies may exist. In this study, we show that the first 77 bp of L1Tc (Pr77) (also present in the T. cruzi non-autonomous retrotransposon NARTc, in the Trypanosoma brucei RIME/ingi elements, and in the T. cruzi, T. brucei and Leishmania major degenerate L1Tc/ingi-related elements [DIREs]) behave as a promoter element that activates gene transcription. The transcription rate promoted by Pr77 is 10–14-fold higher than that mediated by sequences located upstream from the T. cruzi tandemly repeated genes KMP11 and the GAPDH. The Pr77 promoter-derived mRNAs initiate at nucleotide +1 of L1Tc, are unspliced and translated. L1Tc transcripts show a moderate half life and are RNA pol II dependent. The presence of an internal promoter at the 5′ end of L1Tc favors the production of full-length L1Tc RNAs and reinforces the hypothesis that this mobile element may be naturally autonomous in its transposition.This work was supported by BMC2003–00834 from Plan Nacional IþDþI (MEC, Spain) and PAI ref. P05-CVI-01227 (Junta de Andalucı´ a, Spain). S.R.H. was supported by a MEC Predoctoral Fellowship, Spain. Funding to pay the Open Access publication charge was provided by PAI CVI-155 (Junta de Andalucia, Spain).Peer reviewed