Transcription factor that plays a central role in developing and mature glia. Specifically activates expression of myelin genes, during oligodendrocyte (OL) maturation, thereby playing a central role in oligodendrocyte maturation and CNS myelination. The transactivation domains TAM and TAC (for transactivation domain in the middle and at the C-terminus, respectively) are required to contact transcriptional coactivators and basal transcriptional machinery components and thereby induce gene transactivation.