2.

IL-1β represses TβRII expression via Sp1 site at position −25. A: HAC, transfected with an Sp1 consensus sequence (Sp1 decoy), were incubated in DMEM + 2% FCS in the presence or not of IL-1β (1 ng/ml) for 24 hrs. Thereafter, TβRII mRNA versus GAPDH level was determined by RT-PCR. B: Subconfluent cultures of chondrocytes were treated with IL-1β (1 ng/ml) for 48 hrs in the presence or absence of mithramycin (100 or 150 nM). TβRII expression was analysed at mRNA level by real-time RT-PCR (B).