Reciprocal regulation of expression of the human adenosine 5′‐triphosphate binding cassette, sub‐family A, transporter 2 (ABCA2) promoter by the early growth response‐1 (EGR‐1) and Sp‐family transcription factors

摘要

The human ABCA2 transporter gene encodes a member of a large family of ATP‐binding proteins that transport a variety of macromolecules across biological membranes. We have performed luciferase reporter gene assays with promoter constructs comprising the 5′‐flanking region to identify cis‐regulatory DNA elements and have mapped the minimal promoter region to 321 bp upstream of the translation start site. We have discovered a functional role for two GC‐boxes located in the proximal promoter of the ABCA2 gene that contain overlapping sites for the EGR‐1 and Sp1 transcription factors. We observed that oligonucleotides containing overlapping EGR‐1/Sp1 sites bind the Sp1, Sp3 and Sp4 transcription factors. When BE(2)‐M17 cells were treated with phorbol 12‐myristate 13‐acetate, we observed inducible expression and binding of the EGR‐1 transcription factor to the two GC‐boxes. Transfection of Sp1, Sp3 or Sp4 expression constructs into Drosophila S2 induced a dose‐dependent increase in transcriptional activation of the ABCA2 promoter, but transfection of EGR‐1 alone failed to activate transcription. When increasing amounts of EGR‐1 were transfected into the BE(2)‐M17 neuroblastoma cells we observed a dose‐dependent decrease in expression of the ABCA2 promoter, although expression of the endogenous ABCA2 gene increased following transfection of EGR‐1.