Multiple DNA Elements Responsible for Transcriptional Regulation of the
Ornithine Decarboxylase Gene by Protein Kinase A
Mitchell S. Abrahamsen, Run-Sheng Li, Walter Dietrich-Goetz, and David
R. Morris
Transcription of the ornithine decarboxylase (ODC) gene is rapidly elevated
by activation of protein kinase A (PKA). The additive influence of three
cis-acting elements is responsible for this regulation in an adrenal carcinoma
cell line. Two sites, CRE2 at -48 base pairs (bp) relative to the start
of transcription and CRE3 at +95 bp, are identical to the core motif of
the cAMP-responsive element (CRE) of the somatostatin gene and are conserved
in the mouse, rat and human ODC genes. Mutation of CRE2 resulted in a substantial
decrease in basal promoter activity, as well as a 5-fold decrease in inducibility
of the ODC promoter by PKA. CRE3 did not contribute to the basal activity
of the ODC promoter, but mutation of this site resulted in a 2-fold decrease
in inducibility by PKA. Deletion of a 45-bp sequence (GC-box) located 5'
of CRE2, also resulted in a 2-fold decrease in inducibility of the ODC
promoter. DNase I protection revealed the presence of protein binding at
CRE2, the TATA box and the GC-box of the ODC promoter. Mutation of CRE2
resulted in loss of protection of this sequence, as well as the 3' extension
of the footprint over the TATA box, without affecting interactions at the
GC box. Antibodies to the well characterized CRE-binding protein CREB recognized
proteins binding to CRE2, suggesting that binding of CREB, or an antigenically
related protein, is important for the activity of CRE2. Additionally, recombinant
CREB bound to a DNA probe containing the CRE2 sequence.