The CUL4B‐based E3 ubiquitin ligase regulates mitosis and brain development by recruiting phospho‐specific DCAFs

The paralogs CUL4A and CUL4B assemble cullin‐RING E3 ubiquitin ligase (CRL) complexes regulating multiple chromatin‐associated cellular functions. Although they are structurally similar, we found that the unique N‐terminal extension of CUL4B is heavily phosphorylated during mitosis, and the phosphor...

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Published in:The EMBO journal 2023-09, Vol.42 (17), p.e112847-n/a
Main Authors: Stier, Anna, Gilberto, Samuel, Mohamed, Weaam I, Royall, Lars N, Helenius, Jonne, Mikicic, Ivan, Sajic, Tatjana, Beli, Petra, Müller, Daniel J, Jessberger, Sebastian, Peter, Matthias
Format: Article
Language:English
Subjects:
Actin
Binding
Biochemical analysis
Brain
Cell division
Cellular structure
Chromatin
Cullin
Cullin 4B
Cytoskeleton
cytoskeleton regulation
Forebrain
Immunoprecipitation
Intellectual disabilities
Mitosis
Mutation
N-Terminus
Neurodevelopment
Organoids
Phosphorylation
Receptors
Scaffolds
Substrates
Ubiquitin
Ubiquitin-protein ligase
ubiquitin–proteasome system
Ventricle
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Summary:The paralogs CUL4A and CUL4B assemble cullin‐RING E3 ubiquitin ligase (CRL) complexes regulating multiple chromatin‐associated cellular functions. Although they are structurally similar, we found that the unique N‐terminal extension of CUL4B is heavily phosphorylated during mitosis, and the phosphorylation pattern is perturbed in the CUL4B‐P50L mutation causing X‐linked intellectual disability (XLID). Phenotypic characterization and mutational analysis revealed that CUL4B phosphorylation is required for efficient progression through mitosis, controlling spindle positioning and cortical tension. While CUL4B phosphorylation triggers chromatin exclusion, it promotes binding to actin regulators and to two previously unrecognized CUL4B‐specific substrate receptors (DCAFs), LIS1 and WDR1. Indeed, co‐immunoprecipitation experiments and biochemical analysis revealed that LIS1 and WDR1 interact with DDB1, and their binding is enhanced by the phosphorylated N‐terminal domain of CUL4B. Finally, a human forebrain organoid model demonstrated that CUL4B is required to develop stable ventricular structures that correlate with onset of forebrain differentiation. Together, our study uncovers previously unrecognized DCAFs relevant for mitosis and brain development that specifically bind CUL4B, but not the CUL4B‐P50L patient mutant, by a phosphorylation‐dependent mechanism. Synopsis The cullin‐RING E3 ligase family CRL4 is based on two structurally similar scaffold subunits, CUL4A and CUL4B. Here, the unique N‐terminal extension in the CUL4B paralogue is found to be heavily phosphorylated in mitosis, which promotes the recruitment of a specific set of substrate receptors (DCAFs). The N-terminus of CUL4B is phosphorylated during mitosis, and efficient phosphorylation is required for proper progression through mitosis. CRL4B, but not CRL4A, recruits phospho‐specific DCAFs such as LIS1 and WDR1, which are involved in cytoskeleton regulation. CUL4B is required to develop stable ventricular structures in human forebrain organoids. A CUL4B patient mutation (P50L) alters mitotic phosphorylation and leads to X‐linked intellectual disability (XLID). Heavy phosphorylation of a unique N‐terminal extension distinguishing CUL4B from its paralogue CUL4A promotes the recruitment of a specific set of substrate receptors involved in cytoskeleton regulation.
ISSN:0261-4189
1460-2075
DOI:10.15252/embj.2022112847