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Nature Structural & Molecular Biology 15, 849–857 (1 August 2008) | doi:10.1038/nsmb.1457

A conserved face of the Jagged/Serrate DSL domain is involved in Notch trans-activation and cis-inhibition

Jemima Cordle , Steven Johnson , Joyce Zi Yan Tay , Pietro Roversi , Marian B Wilkin , Beatriz Hern|[aacute]|ndez de Madrid , Hideyuki Shimizu , Sacha Jensen , Pat Whiteman , Boquan Jin , Christina Redfield , Martin Baron , Susan M Lea & Penny A Handford

The Notch receptor and its ligands are key components in a core metazoan signaling pathway that regulates the spatial patterning, timing and outcome of many cell-fate decisions. Ligands contain a disulfide-rich Delta/Serrate/LAG-2 (DSL) domain required for Notch trans-activation or cis-inhibition. Here we report the X-ray structure of a receptor binding region of a Notch ligand, the DSL-EGF3 domains of human Jagged-1 (J-1DSL-EGF3). The structure reveals a highly conserved face of the DSL domain, and we show, by functional analysis of Drosophila melanogster ligand mutants, that this surface is required for both cis- and trans-regulatory interactions with Notch. We also identify, using NMR, a surface of Notch-1 involved in J-1DSL-EGF3 binding. Our data imply that cis- and trans-regulation may occur through the formation of structurally distinct complexes that, unexpectedly, involve the same surfaces on both ligand and receptor.