Constitutes a precursor of the transcription factor. Mediates the autocatalytic cleavage that releases the Myelin regulatory factor, N-terminal component that specifically activates transcription of central nervous system (CNS) myelin genes.; Membrane-bound part that has no transcription factor activity and remains attached to the endoplasmic reticulum membrane following cleavage.; Transcription factor that specifically activates expression of myelin genes such as MBP, MOG, MAG, DUSP15 and PLP1 during oligodendrocyte (OL) maturation, thereby playing a central role in oligodendrocyte maturation and CNS myelination. Specifically recognizes and binds DNA sequence 5'-CTGGYAC-3' in the regulatory regions of myelin-specific genes and directly activates their expression. Not only required during oligodendrocyte differentiation but is also required on an ongoing basis for the maintenance of expression of myelin genes and for the maintenance of a mature, viable oligodendrocyte phenotype.