A potential H-DNA element in the MUC1 promoter does not influence transcription.

A purine/pyrimidine mirror repeat element (M-PMR3) in the MUC1 promoter has been shown to form H-DNA under in vitro conditions. We investigated this element for biological function in the regulation of transcription of this gene. Chloramphenicol acetyltransferase reporter-promoter constructs were prepared in which the mirror repeat element (PMR3) was intact, deleted, or modified, and their activities were evaluated by transient transfection assays into the cell lines Capan-2, PANC1, and HT-29. Deletion or modification of M-PMR3 increased expression of chloramphenicol acetyltransferase activity in MUC1-expressing cells; however, a role for an H-DNA structure in this activity was not supported by the results.