FIGURE 7.

RAR-β is upstream of HNF-1β in ATRA-mediated stimulation of DRA expression. Caco-2 cells were transfected with scrambled, HNF-1β-specific and RAR-β-specific small interfering RNA (siRNA) for 48 h. The cells were then treated with 10 μm ATRA for an additional 24 h. Total RNA and protein was extracted. A, (i) quantitative real-time RT-PCR was performed utilizing HNF-1β gene specific primers and (ii) protein expression of HNF-1β was examined using anti-HNF1-β antibody in cells where RAR-β was silenced. B, (i) quantitative real-time RT-PCR was performed utilizing RAR-β gene-specific primers and (ii) protein expression of RAR-β was examined using anti-RAR-β antibody in the cells where HNF-1β was silenced. Data represent the relative expression of HNF-1β or RAR-β normalized to the respective GAPDH mRNA (internal control) levels. Results are expressed as fold-changes in mRNA levels compared with control. For protein expression, a representative blot of 3 separate experiments is shown. Results of densitometric analysis are expressed as HNF-1β or RAR-β/GAPDH levels. Values represent mean ± S.E. of 3 different experiments. *, p < 0.05; **, p < 0.001 compared with control.