Oligonucleotide decoy mimicking αA-crystallin-binding protein 1 binding site on mouse Col2a1 enhancer stimulates transcription from the adjacent Col2a1 promoter in chondrogenic ATDC5 cell

A 48-bp sequence element in intron 1 of the alpha1(II) collagen gene (Col2a1) acts as an enhancer of Col2a1 transcription and contains binding sites for the transcription activator SOX9 and repressor alphaA-crystallin-binding protein 1 (CRYBP1). We hypothesized that abrogating CRYBP1 binding should increase transcription from a promoter associated with the Col2a1 enhancer. We tested this hypothesis by cotransfecting an oligonucleotide (ODN) decoy for CRYBP1 and a luciferase-based reporter vector under the transcriptional control of the Col2a1 promoter linked to the 100-bp enhancer in chondrogenic ATDC5 cells. As a control, we used decoy ODN corresponding to the SOX9 binding site. Transfection with CRYBP1 decoy increased luciferase activity by >2.5-fold in the absence or presence of insulin, whereas SOX9 decoy ODN decreased luciferase activity to about 50% under similar conditions. In addition, the repressive effect of interleukin-1 on Col2a1 transcription through decreasing SOX9 messenger ribonucleic acid (mRNA) expression and increasing CRYBP1 mRNA expression, was counteracted by CRYBP1 decoy ODN. These results provide a rationale for gene therapy in degenerative joint diseases by elevating Col2a1 expression in chondrocytes through oligomimetics of repressor binding sites.