Characterization and regulation of the nonerythroid porphobilinogen deaminase promoter

The non-erythroid porphobilinogen deaminase (E.C. 4.3.1.8) promoter was investigated according to sequence changes and transcriptional activity. The minimal promoter sequence required for maximal transcription, was localized by deletion mapping to -243 to -115 relative to the translational start site. A negative transcriptional element was found between -55 and +1, indicating a repression mechanism. A new polymorphism was identified, at position -235 within the minimal promoter, both in acute intermittent porphyria patients and healthy control subjects. The polymorphic variants did not affect expression of cloned promoter fragments under the conditions used.