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

Abstract

Purα, a single-stranded DNA binding protein, recognizes a PUR element (GGN repeat). We have reported that Purα binds to a single-stranded oligonucleotide probe containing the cAMP response element (CRE) of rat somatostatin gene using a gel mobility shift assay. Here, we showed that Purα binds to the probe only in the presence of a PUR element by a more detailed characterization. We also examined the effects of Purα on the enhancer activity of the somatostatin CRE in PC12 cells using the reporter gene assay. Transfected Purα suppressed the CRE enhancer activity stimulated by forskolin (which increases intracellular cAMP), but suppression was not observed when the PUR element was deleted. The neurite extension induced by forskolin was inhibited by the transfection of Purα, but that by NGF was not suppressed. The c-fos mRNA induced by forskolin, but not by NGF, was also suppressed by Purα transfection. These results indicate that Purα suppresses the biological activities induced by forskolin, but not by NGF, in PC12 cells and that Purα could interfere with a cAMP-CRE signal pathway.