Ubiquitin Proteasome Pathway Participate In Spen Homolog MINT-mediated Transcription Regulation

In mammalian cells, the ubiquitin-proteasome pathway is the principal system that mediates selectively the degradation of short-lived proteins related to such cellular activities as cell cycle progression, the response to stress, antigen processing, signal transduction, transcriptional regulation, DNA repair, apoptosis, and organelle biogenesis. Ubiquitylation occurs as a result of the sequential action of four classes of enzymes, E1 or ubiquitin activating enzyme, E2 or ubiquitin conjugating enzyme, E3 or ubiquitin protein ligase and E4 or ubiquitin chain assembly factor. E1, the first enzyme in the ubiquitylation pathway, forms a thiol-ester bond between its active site cysteine and the carboxyl-terminal glycine of ubiquitin. The activated ubiquitin on E1 is subsequently transferred to the active site cysteine of an E2 by transesterification. E3 binds ubiquitin-charged E2 and substrate and facilitates formation of an isopeptide linkage between the carboxyl-terminal glycine of ubiquitin and the ε amino group of an internal lysine residue on the substrate, or an ubiquitin already attached to the protein. Ubiquitin chain assembly factor or E4 is...