title: Structural analysis of Notch-regulating Rumi reveals basis for pathogenic mutations.
abstract: Rumi O-glucosylates the EGF repeats of a growing list of proteins essential in metazoan development, including Notch. Rumi is essential for Notch signaling, and Rumi dysregulation is linked to several human diseases. Despite Rumi's critical roles, it is unknown how Rumi glucosylates a serine of many but not all EGF repeats. Here we report crystal structures of Drosophila Rumi as binary and ternary complexes with a folded EGF repeat and/or donor substrates. These structures provide insights into the catalytic mechanism and show that Rumi recognizes structural signatures of the EGF motif, the U-shaped consensus sequence, C-X-S-X-(P/A)-C and a conserved hydrophobic region. We found that five Rumi mutations identified in cancers and Dowling-Degos disease are clustered around the enzyme active site and adversely affect its activity. Our study suggests that loss of Rumi activity may underlie these diseases, and the mechanistic insights may facilitate the development of modulators of Notch signaling.
authors.affiliation: Biology Department, Brookhaven National Laboratory, Upton, New York, USA.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Yu
authors.affiliation: Complex Carbohydrate Research Center, the University of Georgia, Athens, Georgia, USA.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takeuchi
authors.affiliation: Complex Carbohydrate Research Center, the University of Georgia, Athens, Georgia, USA.
authors.forename: Megumi
authors.initials: M
authors.lastname: Takeuchi
authors.affiliation: Biology Department, Brookhaven National Laboratory, Upton, New York, USA.
authors.forename: Qun
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Kantharia
authors.affiliation: Complex Carbohydrate Research Center, the University of Georgia, Athens, Georgia, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Haltiwanger
authors.affiliation: Biology Department, Brookhaven National Laboratory, Upton, New York, USA.|Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA.
authors.forename: Huilin
authors.initials: H
authors.lastname: Li
mesh_terms: D000818:Animals; D055162:Biocatalysis; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D051379:Mice; D009154:Mutation; D011487:Protein Conformation
chemical_list: D029721:Drosophila Proteins; D005964:Glucosyltransferases; C527374:Rumi protein, Drosophila