Meta-Biol

• Pathways

The Fringe family (CAZy family GT31) of glycosyltransferases in mammals includes LFNG (lunatic fringe; MIM:602576), MFNG (manic fringe; MIM:602577) and RFNG (radical fringe; MIM:602578). Fringe enzymes function in the Golgi apparatus where they initiate the elongation of O-linked fucose on fucosylated peptides by the addition of a beta-1,3-N-acetylglucosaminyl group (GlcNAc) (Moloney et al. 2000). Fringe enzymes elongate conserved O fucosyl residues conjugated to EGF repeats of NOTCH, modulating NOTCH activity (Cohen et al. 1997, Johnston et al. 1997) by decreasing the affinity of NOTCH extracellular domain for JAG ligands (Bruckner et al. 2000). In developing mouse thymocytes, Lfng enhances Notch1 activation by Dll4, resulting in prolonged Notch1 signaling that promotes self-renewal of TCR-beta-expressing progenitors (Yuan et al. 2011). Since the exact preference, if any, of fringe enzymes for NOTCH O-fucose sites is not known, the extension of an O-fucosyl residue at an unknown protein position is shown.