Fig. 2.

RARβ activates Saa3 transcription by binding directly to its promoter. (A) RARβ binding to the Saa3 promoter was measured by ChIP assay with an anti-RARβ antibody. Bound promoter sequences were detected by qPCR with primers flanking each predicted retinoic acid response element (RARE, indicated by *). (B) The RARE located 224 nt upstream of the Saa3 start site (RARE -224) was further validated by ChIP. n = 3 replicates per group; data represent three independent experiments. (C) Luciferase reporter assay for Saa3 promoter activity. A 4,103-bp fragment of the Saa3 promoter was fused to a firefly luciferase reporter and RARE -224 was mutated as shown in A. MODE-K cells were transfected with the wild-type (wt) or mutant (mut) reporter plasmids or empty vector and were treated with retinol and LPS for 24 h. n = 3 replicates/group; data represent two independent experiments. Means ± SEM are plotted. *P < 0.05; **P < 0.01, as determined by Student’s t test.