Specific domain of cGMP-dependent protein kinase I beta but not I alpha, functions as a transcriptional activator in yeast

Recently, cyclic GMP-dependent protein kinase (cGK) was shown to translocat e to the nucleus and regulate gene transcription. To determine whether cGK I proteins function as transcriptional activators,we produced the construct s of cGK I alpha or I beta fused with the DNA binding domain of the yeast t ranscriptional activator GAL4. Here, we demonstrate that the amino-terminal region of cGK I beta (amino acids 1-107) exhibits transcriptional activati on in yeast, However, full-length cGK I alpha and I beta and the amino-term inal region of cGK I alpha had no transcriptional activation function, Amin o acid replacement in the leucine zipper motif of the amino-terminal region of cGK I beta substantially reduced transcriptional activation, These resu lts suggest that the I beta-specific region in cGK I proteins may interact with other proteins by way of the leucine zipper motif and has a transcript ional activation function.