Gene expression of type II collagen is regulated by direct interaction with Kruppel-like factor 4 and AT-rich interactive domain 5B.

We have previously found and characterized two pairs of enhancer elements, E1 and E2, in the type II collagen alpha 1 chain (COL2A1) gene. Subsequent studies have suggested that these enhancers function differently in the regulation of gene expression. For example, histone deacetylase 10 modifies only the E2 enhancer region to affect gene expression. Therefore, in this study, we aimed to clarify the transcriptional complex formed at each enhancer region by identifying transcription factors that specifically bind to each enhancer element. To this end, we used chondrocytic cell lines established using our unique silent reporter system and overexpressed candidate transcription factors in these cells. We found two transcription factors, other than the SOX trio, that directly bound to COL2A1 and regulated its expression. The first was Kruppel-like factor-4 (KLF4), which bound to the promoter proximal region, and the second was AT-rich interactive domain 5B (ARID5B) which bound to the E1 enhancer element. Further studies are needed to identify factors that specifically bind to the E2 enhancer element. In any case, our findings provide an important insight into the molecular mechanisms underlying the regulation of COL2A1. In this paper, we reevaluated the previous analysis of transcription factors involved in the regulation of COL2A1 expression.