The length of a ubiquitin chain is a general determinant for selective recognition by ubiquitin-binding proteins

Abstract

The attachment of differently linked ubiquitin (Ub) chains of varying length to proteins is a prevalent posttranslational modification in eukaryotic cells. The fate of a modified protein is determined by Ub-binding proteins (UBPs) that interact with Ub chains in a linkage-selective manner. Therefore, proteome-wide interaction studies using differently linked Ub chains have become an increased focus of research activities. However, the impact and functional consequences of chain length on the binding selectivity of UBPs remain mostly elusive, due to a lack of available tools and sufficient amounts of pure, length-defined Ub chains. Here, we generated linkage- and length-defined Ub chains using click-chemistry and Gel Eluted Liquid Fraction Entrapment Elelectrophoresis (GELFrEE) fractionation and employed such defined polymers in affinity-based enrichment assays to identify length- and linkage-selective interactors on a proteome-wide scale. For the first time, this revealed that the length of a Ub chain has generally a major impact on its ability to be selectively recognized by UBPs.