Positive and negative effects of deletions and mutations within the 5' flanking sequences of Plasmodium falciparum DNA polymerase delta

Abstract

The DNA polymerase delta gene from Plasmodium falciparum is associated with a 1.76 kb 5' untranslated region and a promoter containing long homopolymeric (dA:dT) tracts and intrinsic DNA curvature. Here, a comprehensive deletion and mutational analysis of the DNA Pol(delta) upstream sequences has been undertaken to define functionally important regions. Removal of promoter-proximal DNA was shown to upregulate luciferase reporter gene expression and the ATG-proximal portion of the 5' untranslated region was required in conjunction with the promoter for reporter activity. In contrast to the ATG-proximal 5' untranslated region, deletion of the central part of the untranslated region had a positive effect on expression. Disruption of a homopolymeric (dA:dT) tract adjacent to the main transcription start site both derepressed gene expression and reduced the intrinsic curvature of DNA fragments containing this sequence.