CHARACTERIZATION OF THE DECAY-ACCELERATING FACTOR GENE PROMOTER REGION

Decay-accelerating factor (DAF) expression modulates susceptibility of cells to autologous complement attack. To characterize the regulatory region controlling DAF gene transcription, genomic DNA extending from 815 base pairs (bp) upstream to almost-equal-to 4 kilobases downstream of DAF's AUG codon (designated +1) was cloned and sequenced. The 5' flanking sequence showed 59-76% G+C content (-355 to +1), at least one GC box(es) (-135 to -131), and variable length sequences (from -629 to -285) conforming to the motifs TCCTCC and TC(n). Nuclease S1 digestions and primer extensions localized a major transcriptional start site to -82/ -81, 38 bp downstream of a possible TATA variant, (A)TTTAA. In COS cell transfections, the sequence encompassing -815 to -67 functioned 2.5% as efficiently as the Rous sarcoma virus 3' long terminal repeat, but following deletion upstream of -355 its activity increased almost-equal-to 4-fold. Two octanucleotides exhibiting partial homology to phorbol 12-myristate 13-acetate (PMA) and cAMP responsive elements (PREs and CREs, respectively) were detected, and the respective modulators enhanced transcriptional efficiency 2- and almost-equal-to 10-fold, respectively. Thus, the DAF gene promoter (i) exhibits sequences resembling both conventional and unconventional transcriptional control elements, (ii) possesses a region with negative regulatory activity, and (iii) responds to PMA and cAMP induction presumably via PRE- and CRE-like enhancer elements.