Specific domain of cGMP-dependent protein kinase Ibeta but not Ialpha functions as a transcriptional activator in yeast.

Recently, cyclic GMP-dependent protein kinase (cGK) was shown to translocate to the nucleus and regulate gene transcription. To determine whether cGK I proteins function as transcriptional activators, we produced the constructs of cGK Ialpha or Ibeta fused with the DNA binding domain of the yeast transcriptional activator GAL4. Here, we demonstrate that the amino-terminal region of cGK Ibeta (amino acids 1-107) exhibits transcriptional activation in yeast. However, full-length cGK Ialpha and Ibeta and the amino-terminal region of cGK Ialpha had no transcriptional activation function. Amino acid replacement in the leucine zipper motif of the amino-terminal region of cGK Ibeta substantially reduced transcriptional activation. These results suggest that the Ibeta-specific region in cGK I proteins may interact with other proteins by way of the leucine zipper motif and has a transcriptional activation function.