Unusual features of poly[dT-dG]center dot[dC-dA] stretches in CDS-flankingregions of Trypanosoma cruzi genome

In trypanosomatids, the mechanisms of gene expression regulation are not ye t well understood. The genes are organized into long polycistronic transcri ption units separated by intergenic regions that may contain the signaling information for nucleic acid processing. Poly-dinucleotides are frequent in these regions and have been proposed to be involved in gene expression reg ulation. We analyzed their frequency in CDS-flanking sequences of sense str ands in Trypanosoma cruzi and established that all but poly[dC-dC], poly[dC -dG], and poly[dG-dG] are significantly more frequent than expected by chan ce. Poly[dT-dG](.)[dC-dA] is among the longest and most frequent polydinucl eotides and shows a remarkable strand asymmetry. Furthermore, electrophoret ic mobility shift assays using T. cruzi epimastigotes nuclear extracts demo nstrated the existence of at least, one sequence specific single-strand bin ding activity for each strand. These results strongly suggest that poly[dT- dG](.)[dC-dA] sequence is involved in regulatory mechanisms of relevance fo r the parasite biology. (C) 2001 Academic Press.