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 (By similarity). 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 during oligodendrocyte (OL) maturation, thereby playing a central role in oligodendrocyte maturation and CNS myelination. Homotrimer. Translocates from the cytoplasm to the nucleus upon autocatalytic cleavage. The peptidase S74 domain, also named Intramolecular Chaperone Auto-processed (ICA) domain or Intramolecular Chaperone Domain (ICD), has protease activity and mediates autocatalytic processing of the protein to generate the Myelin regulatory factor, N-terminal active transcription factor and the Myelin regulatory factor, C-terminal components. Follows autocatalytic cleavage via the peptidase S74 domain. Autoprocessing is apparently constitutive and is essential for transcriptional activity. Belongs to the MRF family.