KLF6 and HSF4 transcriptionally regulate multidrug resistance transporters during inflammation

Endotoxin-induced inflammation alters the hepatic expression of the drug efflux transporter genes mdr1b (Abcb1b) and mrp3 (Abcc3) in rats. In this study, we identified a novel kruppel-like zinc finger protein 6 (KLF6) cis-element on the rat mdr1b promoter which is important for basal activity and IL-1β and endotoxin-mediated induction in gene transcription. Interestingly, KLF6 also functioned as a negative transcriptional regulator, inhibiting TNF-α-mediated induction of mdr1b. Furthermore, novel CCAAT/enhancer binding protein β (C/EBPβ) and heat shock factor 4 (HSF4) transcription binding sites were identified on the rat mrp3 promoter. Deletion of the HSF4 element significantly increased transcriptional activity of the mrp3 gene when exposed to TNF-α. Endotoxin treatment significantly affected transcriptional activity only in C/EBPβ and HSF4 double deletion mrp3 promoter constructs. In summary, KLF6 and HSF4 are stimuli-specific regulatory elements which may be important in the control of the rat mdr1b and mrp3 genes during health and disease.