Entamoeba histolytica EhPgp5 transcriptional activation depends on putative emetine response elements

The multidrug resistance EhPgp5 gene promoter is active in drug resistant clone C2 trophozoites and its activity increases when trophozoites are cultured in the presence of emetine, suggesting that the EhPgp5 gene shows an inducible drug dependent mechanism. We analyzed different promoter fragments to detect those regions that activate transcription in the presence of emetine. Trophozoites were transfected with p375Pgp5, p259Pgp5, p187Pgp5, and p76Pgp5 plasmids and incubated with different emetine concentrations. p375Pgp5 and p259Pgp5 plasmids were able to drive CAT expression in A and C2 trophozoites only in the presence of emetine. CAT activity was turned off in the absence of drug. Interestingly, no CAT activity was detected in the presence or in the absence of emetine with p187Pgp5 plasmid in which 59 bp were deleted at the 5' end of the EhPgp5 minimal promoter (p259Pgp5). These results suggest that the overexpression of the EhPgp5 gene is a consequence of transcriptional activation of the gene promoter by putative drug responsive elements, located within the -111 to -170 bp of the transcription initiation site.