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

The CO(2)-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 CO(2) 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 CO(2) regulation for rbc genes. The decoy oligonucleotide approach to cyanobacteria provides a simple and excellent tool for investigating transcriptional regulation in vivo.