Figure 6 Impact of p300 and cyclic AMP response element‐binding protein (CBP) overexpression on matrix metalloproteinase 13 (MMP13) mRNA and promoter activity. (A) Chondrocytes were either not transfected or transfected with pCMVβ or cytomegalovirus (CMV)‐p300 vectors (2 μg each), and total cellular protein (40 μg) was analysed after 48 h by western blotting for p300 and β actin levels. (B,C) Chondrocytes transfected with p300 or CBP expression vectors (2 μg) for 48 h were further treated for 24 h as indicated and MMP13 and glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) mRNAs were analysed by reverse transcriptase‐PCR. (D) Chondrocytes were cotransfected with MMP13 luciferase promoter (4 μg), Renilla luciferase (4 μg) vectors and pCMVβ or pCMVβ‐p300 or pCMVβ‐CBP (2 μg each) and luciferase activity was measured. The values are mean (SD) of three separate experiments. IFN, interferon; IL, interleukin.