Distinct Roles of the Chromosomal Passenger Complex in the Detection of and Response to Errors in Kinetochore-Microtubule Attachment

Abstract

Summary The Chromosomal Passenger Complex (CPC) localizes to centromeres in early mitosis to activate its subunit Aurora B kinase. However, it is unclear if centromeric CPC localization contributes to CPC functions beyond Aurora B activation. Here, we show that an activated CPC that cannot localize to centromeres supports functional assembly of the outer kinetochore, but is unable to correct errors in kinetochore-microtubule attachment in Xenopus egg extracts. We find that CPC has two distinct roles at centromeres: one to properly phosphorylate Ndc80 to regulate attachment, and a second, conserved kinase-independent role in the proper composition of inner kinetochore proteins. Although a fully assembled inner kinetochore is not required for outer kinetochore assembly, we find it is essential to recruit tension indicators, such as BubR1 and 3F3/2, to erroneous attachments. Thus, centromeric CPC is necessary for tension-dependent removal of erroneous attachments, and for the kinetochore composition required to detect tension loss.

Untangling the contribution of Haspin and Bub1 to Aurora B function during mitosis

“…Because activation of Aurora B depends on clustering of the CPC (Kelly et al, 2007, 2010; Wang et al, 2011), clustering and activation of Aurora B most likely takes place at an alternative location, in the absence of Haspin and Bub1 activity. This could simply be chromatin, as we observed low levels of Aurora B dispersed over the chromatin in Bub1-inhibited Haspin CM cells, and in Xenopus laevis egg extracts this was shown to be sufficient for the activation of Aurora B kinase activity (Haase et al, 2017; Kelly et al, 2007). Alternatively, recent work proposed a role for microtubules that traverse the centromere in depositing active Aurora B from the centromere at the kinetochore (Trivedi et al, 2019).…”

“…We deem it unlikely that a microtubule-associated pool of the CPC is responsible for the KT substrate phosphorylation in Bub1-inhibited Haspin CM cells because we observed no difference in Hec1 phosphorylation in either low (0.33 µM) or high (3.3 µM) concentrations of nocodazole. However, we cannot exclude that the CPC core complex, consisting of Borealin, Survivin, and the N terminus of INCENP, might play a role in Aurora B–dependent KT substrate phosphorylation independently of microtubule binding and inner centromere clustering of Aurora B (Haase et al, 2017). Finally, a potential third, transient kinetochore-associated pool of Aurora B, one that does not depend on Haspin and Bub1 kinase activity, may phosphorylate the KMN network (Caldas et al, 2013; DeLuca et al, 2011; Fischböck-Halwachs et al, 2019; García-Rodríguez et al, 2019; Broad et al, 2020).…”

Enrichment of Aurora B kinase at the inner kinetochore controls outer kinetochore assembly

“…Outer kinetochore assembly is entirely dependent on the phosphorylation of Dsn1 by Aurora B kinase in Xenopus egg extracts In Xenopus egg extracts, the assembly and maintenance of kinetochores is completely dependent on the mitotic kinase Aurora B, but the underlying phosphosubstrates are unclear (Emanuele et al, 2005(Emanuele et al, , 2008Haase et al, 2017). In human, chicken, and yeast cells, Aurora B phosphorylation of multiple residues within the Dsn1 subunit of the Mis12C plays a partial role in kinetochore assembly ( Fig.…”

Aurora B-INCENP localization at centromeres/inner kinetochores is essential for chromosome bi-orientation in budding yeast

“…Intriguingly, in the Xenopus egg extract system, the inner kinetochore was not fully assembled when INCENP lacked its N-terminus (in contrast to human cells); in this circumstance, this INCENP mutant could no longer support error correction even if the outer kinetochore assembly seemed normal [40]. Therefore, inner kinetochore components may indeed support Aurora B-INCENP localization and error correction, independently of Survivin, in vertebrate cells.…”