PT  - JOURNAL ARTICLE
AU  - Corinne A. Tovey
AU  - Chisato Tsuji
AU  - Alice Egerton
AU  - Fred Bernard
AU  - Antoine Guichet
AU  - Marc de la Roche
AU  - Paul T. Conduit
TI  - Auto-inhibition of Cnn binding to γ-TuRCs prevents ectopic microtubule nucleation and cell division defects
AID  - 10.1101/2020.10.05.326587
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2020.10.05.326587
4099  - http://biorxiv.org/content/early/2021/03/26/2020.10.05.326587.short
4100  - http://biorxiv.org/content/early/2021/03/26/2020.10.05.326587.full
AB  - γ-tubulin ring complexes (γ-TuRCs) nucleate microtubules. They are recruited to centrosomes in dividing cells via binding to N-terminal CM1 domains within γ-TuRC-tethering proteins, including Drosophila Cnn. Binding promotes microtubule nucleation and is restricted to centrosomes in dividing cells, but the mechanism regulating binding remains unknown. Here we identify an extreme N-terminal “CM1 auto-inhibition” (CAI) domain found specifically within the centrosomal isoform of Cnn (Cnn-C) that inhibits γ-TuRC binding. Robust binding occurs after removal of the CAI domain or with the addition of phospho-mimetic mutations, suggesting that phosphorylation helps relieve inhibition. We show that regulation of Cnn binding to γ-TuRCs is isoform-specific and that mis-regulation of binding can result in ectopic cytosolic microtubules and major defects during cell division. We also find that human CDK5RAP2 is auto-inhibited from binding γ-TuRCs, suggesting conservation across species. Overall, our results shed light on how and why CM1 domain binding to γ-TuRCs is regulated.Summary (for the online JCB table of contents and alerts) We show that auto-inhibition regulates the binding between microtubule nucleating complexes and proteins that tether them to sites of microtubule nucleation. Failure to properly regulate this binding can lead to ectopic cytosolic microtubule nucleation and major defects during cell division.Competing Interest StatementThe authors have declared no competing interest.