Transcription factor that, in osteoblasts, activates the decoy receptor for RANKL, TNFRSF11B, which in turn regulates osteoclast differentiation. Acts in synergy with the Wnt-responsive LEF1/CTNNB1 pathway. Recognizes variations of the palindromic sequence 5'-ATTCCCNNGGGAATT-3' (By similarity). Forms either a homodimer or a heterodimer with a related family member (By similarity). Interacts with SIX1 (PubMed:27923061). Belongs to the COE family.