CO2 response for expression of ribulose-1,5-bisphosphate carboxylase/oxygenase genes is inhibited by AT-rich decoy in the cyanobacterium

The CO2-regulatory function of the AT-rich element in the promoter for ribulose-1,5-bisphosphate carboxylase/oxygenase (rbc) genes in the cyanobacterium Synechococcus sp. PCC7002 was analyzed using the transcription factor decoy approach. Double-stranded phosphorothioate AT-rich oligonucleotides with high affinity for a sequence-specific DNA-binding protein were successfully introduced into cyanobacterial cells in culture without any transfection reagent. The AT-rich decoy oligonucleotides interfered with CO2 regulation of rbc expression by blocking the binding of the sequence-specific DNA-binding protein, indicating that the AT-rich element plays a critical role in CO2 regulation for rbc genes. The decoy oligonucleotide approach to cyanobacteria provides a simple and excellent tool for investigating transcriptional regulation in vivo. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.