Structural basis for ubiquitylation by HOIL-1

Qilong Wu; Marios G Koliopoulos; Katrin Rittinger; Benjamin Stieglitz

doi:10.3389/fmolb.2022.1098144

Structural basis for ubiquitylation by HOIL-1

Front Mol Biosci. 2023 Jan 6:9:1098144. doi: 10.3389/fmolb.2022.1098144. eCollection 2022.

Authors

Qilong Wu¹, Marios G Koliopoulos², Katrin Rittinger², Benjamin Stieglitz¹

Affiliations

¹ Department of Biochemistry, School of Biological and Behavioural Sciences, Queen Mary University of London, London, United Kingdom.
² Molecular Structure of Cell Signalling Laboratory, The Francis Crick Institute, London, United Kingdom.

Abstract

The linear ubiquitin chain assembly complex synthesises linear Ub chains which constitute a binding and activation platform for components of the TNF signalling pathway. One of the components of LUBAC is the ubiquitin ligase HOIL-1 which has been shown to generate oxyester linkages on several proteins and on linear polysaccharides. We show that HOIL-1 activity requires linear tetra-Ub binding which enables HOIL-1 to mono-ubiquitylate linear Ub chains and polysaccharides. Furthermore, we describe the crystal structure of a C-terminal tandem domain construct of HOIL-1 comprising the IBR and RING2 domains. Interestingly, the structure reveals a unique bi-nuclear Zn-cluster which substitutes the second zinc finger of the canonical RING2 fold. We identify the C-terminal histidine of this bi-nuclear Zn-cluster as the catalytic base required for the ubiquitylation activity of HOIL-1. Our study suggests that the unique zinc-coordinating architecture of RING2 provides a binding platform for ubiquitylation targets.

Keywords: E3 ligase; HOIL-1L; HOIP; LUBAC; RBCK1; TNF signalling; amylopectinosis; ubiquitin.