Abstract
PSEUDO RESPONSE REGULATOR9 (PRR9), PRR7, and PRR5 are involved in circadian clock mechanism that generates circadian rhythms. PRR9, PRR7, and PRR5 proteins negatively regulate accumulation of mRNA for CARCADIAN CLOCK ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), while the molecular functions of PRR proteins were unknown.
In this report, we analyzed PRR proteins using T87 Arabidopsis cultured cells. The dual-luciferase reporter assay was developed, and the assay allowed us to calculate promoter activity of CCA1 gene in vivo. Transiently expressed PRR9-CFP, PRR7-CFP, and PRR5-CFP proteins localized in the nuclei of cells, and PRR proteins can repress transcriptional activity of CCA1 promoter. The DEX-GR system revealed the essential role of nuclear localization to PRR function. PRR proteins conjugated to intrinsic transcriptional activator VP16 could activate CCA1 promoter, suggesting that PPR proteins can bind to DNA directly. These results suggested that PRR are nuclear localized proteins and repress CCA1 promoter directly.
