MAU2 and NIPBL Variants Impair the Heterodimerization of the Cohesin Loader Subunits and Cause Cornelia de Lange Syndrome
Résumé
The NIPBL/MAU2 heterodimer loads cohesin onto chromatin. Mutations in NIPBL account for most cases of the rare developmental disorder Cornelia de Lange syndrome (CdLS). Here we report a MAU2 variant causing CdLS, a deletion of seven amino acids that impairs the interaction between MAU2 and the NIPBL N terminus. Investigating this interaction, we discovered that MAU2 and the NIPBL N terminus are largely dispensable for normal cohesin and NIPBL function in cells with a NIPBL early truncating mutation. Despite a predicted fatal outcome of an out-of-frame single nucleotide duplication in NIPBL, engineered in two different cell lines, alternative translation initiation yields a form of NIPBL missing N-terminal residues. This form cannot interact with MAU2, but binds DNA and mediates cohesin loading. Altogether, our work reveals that cohesin loading can occur independently of functional NIPBL/MAU2 complexes and highlights a novel mechanism protective against out-of-frame mutations that is potentially relevant for other genetic conditions. © 2020 The AuthorsParenti et al. describe mutations causative for CdLS that affect the interaction between NIPBL and MAU2, the two subunits of the cohesin loader complex. This study further reveals a protective mechanism that rescues NIPBL expression in the presence of early truncating variants by using alternative translation initiation site. © 2020 The Authors
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