Identification of a cis-acting gene regulatory element from the lemdr1 locus of Leishmania enriettii.

The goal of this work is to identify those elements which control gene expression in the parasitic protozoan, Leishmania enriettii. To date there has been no report of a transcriptional controlling element identified in this parasite. In the present study, we have found that a region of the lemdr1 locus of L. enriettii can down-regulate the steady state mRNA level of the reporter neomycin phosphotransferase gene when it is placed in an extrachromosomal expression vector, pALTneo. Through deletion analysis, we have mapped a putative regulatory sequence to the flanking region upstream of the lemdr1 gene. This cis regulatory element is shown to control gene expression in an orientation-dependent and position independent manner. By performing nuclear run-on analysis, we have demonstrated that this element mainly exerts its effect at the transcriptional level by determining the strandedness of transcription on the pALTneo vector. The identification of this novel cis regulatory element should further our understanding of the transcriptional process in Leishmania and other related trypanosomatids.