Transcription factor required for myelination of differentiated oligodendrocytes. Required for the conversion of oligodendrocytes from the premyelinating to the myelinating state. In the developing central nervous system (CNS), involved in the maintenance in the progenitor stage by promoting the cell cycle. Specifically binds to the 5′-TCAT-3′ DNA sequence (By similarity). Has transcription repressor activity in vitro.