Bezafibrate induces plasminogen activator inhibitor-1 gene expression in a CLOCK-dependent circadian manner.
A functional interaction between peroxisome proliferator-activated receptor alpha (PPARalpha) and components of the circadian clock has been suggested, but whether these transcriptional factors interact to regulate the expression of their target genes remains obscure. Here we used a PPARalpha ligand, bezafibrate, to search for PPARalpha-regulated genes that are expressed in a CLOCK-dependent circadian manner. Microarray analyses using hepatic RNA isolated from bezafibrate treated-wild type, Clock mutant (Clk/Clk), and PPARalpha-null mice revealed that 136 genes are transcriptionally regulated by PPARalpha in a CLOCK-dependent manner. Among them, we focused on the plasminogen activator inhibitor-1 (PAI-1) gene, because its expression typically shows circadian variation, and it has transcriptional response elements for both PPAR and CLOCK. The bezafibrate-induced expression of PAI-1 mRNA was attenuated in Clk/Clk mice and in PPARalpha-null mice. The protein levels of PPARalpha were reduced in Clk/Clk hepatocytes. However, the overexpression of PPARalpha could not rescue bezafibrate-induced PAI-1 expression in Clk/Clk hepatocytes, suggesting that impaired bezafibrate-induced PAI-1 expression in Clk/Clk mice is not due to reduced PPARalpha expression. Luciferase reporter and chromatin immunoprecipitation analyses using primary hepatocytes demonstrated that DNA binding of both PPARalpha and CLOCK is essential for bezafibrate-induced PAI-1 gene expression. Pull-down assays in vitro showed that both PPARalpha and its heterodimerized partner retinoic acid receptor-alpha can serve as potential interaction targets of CLOCK. The present findings revealed that molecular interaction between the circadian clock and the lipid metabolism regulator affects the bezafibrate-induced gene expression.
Oishi
Katsutaka
K
Biological Clock Research Group, Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan.
Koyanagi
Satoru
S
Matsunaga
Naoya
N
Kadota
Koji
K
Ikeda
Eriko
E
Hayashida
Satoru
S
Kuramoto
Yukako
Y
Shimeno
Hiroshi
H
Soeda
Shinji
S
Ohdo
Shigehiro
S
D000818:Animals; D001483:Base Sequence; D001629:Bezafibrate / Q000494:pharmacology*; D056926:CLOCK Proteins / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D002940:Circadian Rhythm; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000187:drug effects*; D051379:Mice; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D047493:PPAR alpha / Q000187:drug effects; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D047493:PPAR alpha; D017395:Plasminogen Activator Inhibitor 1; D056926:CLOCK Proteins; C538944:Clock protein, mouse; D001629:Bezafibrate