The Role of NEDD1 Phosphorylation by Aurora A in Chromosomal Microtubule Nucleation and Spindle Function

Abstract

Chromatin directs de novo microtubule (MT) nucleation in dividing cells by generating a gradient of GTP-bound Ran protein (RanGTP) that controls the activity of a number of spindle assembly factors (SAFs). It is now well established that these MTs are essential for the assembly of a functional bipolar spindle. Although it has been shown that RanGTP-dependent MT nucleation requires γ-tubulin and a number of RanGTP-regulated proteins, the mechanism involved is still poorly understood. We previously showed that the mitotic kinase Aurora A, which is activated in a RanGTP-dependent manner in mitotic cells, has a role in this pathway. Here we show that Aurora A interacts with and phosphorylates the γTURC adaptor protein NEDD1 at a single residue, Ser405. Ser405 phosphorylation is not required for centrosomal MT nucleation but is critical for MT nucleation in the vicinity of the chromosomes in mitotic cells. Moreover, it is essential for RanGTP aster formation and chromatin-driven MT assembly in Xenopus egg extracts. Our data suggest that one important function of Aurora A in mitotic cells is to promote MT nucleation around the chromatin by phosphorylating NEDD1, and thereby to promote functional spindle assembly.

MZT1 regulates microtubule nucleation by linking γTuRC assembly to adapter-mediated targeting and activation

“…Consistent with this notion, the regulatory factors NEDD1 and CDK5RAP2 have a significantly higher turnover rate compared to the γTuRC structural core subunits γ-tubulin, GCP2, GCP3, GCP4, GCP5 and GCP6 (Jakobsen et al, 2011). Moreover, NEDD1 is phosphorylated at multiple sites to specifically control γTuRC function in distinct mitotic nucleation pathways (Gomez-Ferreria et al, 2012;Haren et al, 2009;Johmura et al, 2011;Lüders et al, 2006;Pinyol et al, 2013;Scrofani et al, 2015;Sdelci et al, 2012;Teixidó-Travesa et al, 2010. Future work will show whether human MZT1 is subject to similar regulation.…”

Aurora A kinase and its substrate TACC3 are required for central spindle assembly

“…Interestingly, AurA has been shown to be required for MT nucleation/stabilization through the RanGTP-dependent pathway in the early phases of mitosis [4,8,18]. We have shown here that AurA kinase activity is required during anaphase for central spindle assembly.…”

“…AurA is required for mitotic entry, centrosome maturation and separation and for bipolar spindle formation [3]. Further insights into AurA function have been obtained through the identification of some of its substrates [3][4][5]. One of its best characterized substrate is TACC3, a protein that promotes MT stabilization through its interaction with chTOG/XMAP215 [6].…”

The Cep192-Organized Aurora A-Plk1 Cascade Is Essential for Centrosome Cycle and Bipolar Spindle Assembly

“…In keeping with this notion, it was shown that NEDD1 is phosphorylated by AurA and Plk1 (Haren et al, 2009; Pinyol et al, 2013; Zhang et al, 2009) and that its phosphorylation status depends on Cep192 in mammalian cells (Gomez-Ferreria et al, 2012). …”