dibutyryl-cyclic-gmp and carbobenzoxy-leucyl-leucyl-norvalinal

The rat gastric GATA DNA-binding protein, GATA-6 (GATA-GT1), was stably expressed in CHO-K1 cells. The GATA-6 protein was localized in the nucleus but not in the cytoplasm. Interestingly, when cells were treated with dibutyryl cAMP, the GATA-6 protein was specifically degraded. Such a phenomenon was not observed in the presence of 5'-AMP or dibutyryl cGMP. The cellular level of the GATA-6 protein was restored upon removal of dibutyryl cAMP. Degradation was also induced by cholera toxin, which increased the cellular cAMP concentration, and was inhibited by a protein kinase A inhibitor. However, activators of protein kinase C did not have any effect. The degradation was inhibited by proteasome inhibitors (PSI (benzyloxycarbonyl-Ile-Glu(O-t-Bu)-Ala-leucinal) and MG115 (benzyloxycarbonyl-Leu-Leu-norvalinal)) but not by those of lysosomes and serine proteases. These results suggest that a kinase-mediated protein phosphorylation is the cellular signal for degradation of the GATA-6 protein. This finding constitutes a novel aspect of regulation by GATA DNA-binding proteins, which are essential for developmental processes and tissue-specific transcription.

Topics: Amino Acid Sequence; Animals; Bucladesine; CHO Cells; Cholera Toxin; Conserved Sequence; Cricetinae; Cyclic AMP; Dibutyryl Cyclic GMP; Diglycerides; DNA-Binding Proteins; Fluorescent Antibody Technique, Indirect; Gastric Mucosa; GATA6 Transcription Factor; Inositol 1,4,5-Trisphosphate; Kinetics; Leupeptins; Molecular Sequence Data; Oligopeptides; Proadifen; Protease Inhibitors; Rats; Recombinant Fusion Proteins; Tetradecanoylphorbol Acetate; Transcription Factors; Transfection; Zinc Fingers