FIGURE 5.

AP-1 regulates both basal and IL-1β-induced promoter activity. A, human chondrocyte cells were transfected with pAP-1-Luc (pCMV-(AP-1)₃) and treated with IL-1β or vehicle for 12 h. Relative luciferase activity is calculated as fold change over that of empty vector (pCMV). B, point mutation analysis showing AP-1 site-dependent transcriptional activity of the XT-I promoter in chondrocytes. Luciferase activity of the wild-type (WT) and its mutant constructs (mAP-1–1020, mAP-1–640, and mAP-1–590) were measured in chondrocytes treated (12 h) with IL-1β or vehicle. Relative luciferase activity is calculated as fold change over that of WT in untreated cells. Data are expressed as mean ± S.D. of three separate experiments (*, p < 0.05; #, p < 0.05).