Measuring ubiquitin chain linkage: Rap80 uses a molecular ruler mechanism for ubiquitin linkage specificity

Abstract

DNA double-stranded breaks lead to the recruitment of the Rnf8-Ubc13 complex to the damage site where they catalyse K63-linked ubiquitination. Receptor-associated protein 80 (Rap80) subsequently binds the K63-linked chains and brings with it a BRCA1 complex. Sato et al (2009) solve the crystal structure of the Rap80-UIM1- UIM2:K63-linked diubiquitin complex to show that a contiguous helix spans the UIM1-UIM2 region and defines the relative orientation of the two UIMs for optimal binding to K63-linked chains. This study provides important insights into how protein ubiquitination triggers specific downstream signalling events. © 2009 European Molecular Biology Organization.