Pur alpha, a single-stranded DNA binding protein, suppresses the enhancer activity of cAMP response element (CRE)

Pur alpha, a single-stranded DNA binding protein, recognizes a PUR element (GGN repeat). We have reported that Pur alpha binds to a single-stranded ol igonucleotide probe containing the cAMP response element (CRE) of rat somat ostatin gene using a gel mobility shift assay. Here, we showed that Pur alp ha binds to the probe only in the presence of a PUR element by a more detai led characterization. We also examined the effects of Pur alpha on the enha ncer activity of the somatostatin CRE in PC12 cells using the reporter gene assay. Transfected Pur alpha suppressed the CRE enhancer activity stimulat ed by forskolin (which increases intracellular cAMP), but suppression was n ot observed when the PUR element was deleted. The neurite extension induced by forskolin was inhibited by the transfection of Pur alpha, but that by N GF was not suppressed. The c-fos mRNA induced by forskolin, but not by NGF, was also suppressed by Pur alpha transfection. These results indicate that Pur alpha suppresses the biological activities induced by forskolin, but n ot by NGF, in PC12 cells and that Pur alpha could interfere with a cAMP-CRE signal pathway. (C) 2000 Elsevier Science B.V. All rights reserved.