Aurora B-INCENP Localization at Centromeres/Inner Kinetochores Is Required for Chromosome Bi-orientation in Budding Yeast

Abstract

Summary For proper chromosome segregation in mitosis, sister kinetochores must interact with microtubules from opposite spindle poles (chromosome bi-orientation) [ 1 , 2 ]. To promote bi-orientation, Aurora B kinase disrupts aberrant kinetochore-microtubule interactions [ 3 , 4 , 5 , 6 ]. It has long been debated how Aurora B halts this action when bi-orientation is established and tension is applied across sister kinetochores. A popular explanation for it is that, upon bi-orientation, sister kinetochores are pulled in opposite directions, stretching the outer kinetochores [ 7 , 8 ] and moving Aurora B substrates away from Aurora-B-localizing sites at centromeres (spatial separation model) [ 3 , 5 , 9 ]. This model predicts that Aurora B localization at centromeres is required for bi-orientation. However, this notion was challenged by the observation that Bir1 (yeast survivin), which recruits Ipl1-Sli15 (yeast Aurora B-INCENP) to centromeres, can become dispensable for bi-orientation [ 10 ]. This raised the possibility that Aurora B localization at centromeres is dispensable for bi-orientation. Alternatively, there might be a Bir1-independent mechanism for recruiting Ipl1-Sli15 to centromeres or inner kinetochores [ 5 , 9 ]. Here, we show that the COMA inner kinetochore sub-complex physically interacts with Sli15, recruits Ipl1-Sli15 to the inner kinetochore, and promotes chromosome bi-orientation, independently of Bir1, in budding yeast. Moreover, using an engineered recruitment of Ipl1-Sli15 to the inner kinetochore when both Bir1 and COMA are defective, we show that localization of Ipl1-Sli15 at centromeres or inner kinetochores is required for bi-orientation. Our results give important insight into how Aurora B disrupts kinetochore-microtubule interaction in a tension-dependent manner to promote chromosome bi-orientation.

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

“…Aurora B kinase is also required for the correction of erroneous kinetochore-microtubule attachments (Krenn and Musacchio, 2015). However, the exact roles of the central region in error correction are not fully understood (Vader et al, 2007;Fink et al, 2017;Fischböck-Halwachs et al, 2019;García-Rodríguez et al, 2019), likely due to the fact that the central region also regulates kinetochore assembly, the SAC, and microtubule assembly (current study; Tseng et al, 2010;Wheelock et al, 2017). Future efforts are required to identify additional kinetochore substrates that require high local concentrations of Aurora B.…”

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

“…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).…”

Bub3 and Bub1 maintain the balance of kinetochore-localized Aurora B Kinase and Protein Phosphatase I to Regulate Chromosome Segregation and Anaphase Onset in Meiosis

“…In mitosis, there are four known Ipl1 kinetochore recruitment pathways, with one of the pathways through Bub3/Bub1/Sgo1 (Cho and Harrison, 2011;Edgerton et al, 2016;Fischbock-Halwachs et al, 2019;Garcia-Rodriguez et al, 2019;Kawashima et al, 2010;Peplowska et al, 2014;Verzijlbergen et al, 2014;Yoon and Carbon, 1999). We hypothesize that the Bub3/Bub1/Sgo1 recruitment pathway is crucial for full Ipl1 localization or maintenance in meiosis II.…”

“…For example, the CPC binds histone H3, when phosphorylated by haspin kinases (Edgerton et al, 2016;Kelly et al, 2010;Niedzialkowska et al, 2012;Wang et al, 2010;Yamagishi et al, 2010). And, in budding yeast, two additional pathways are also known to recruit Ipl1 (the budding yeast Aurora B homolog): i) the CPC binds to kinetochore protein Ndc10, a subunit of the Cbf3 centromere-binding complex, and ii) Sli15-Ipl1 binds to the inner kinetochore COMA complex (Cho and Harrison, 2011;Fischbock-Halwachs et al, 2019;Garcia-Rodriguez et al, 2019;Yoon and Carbon, 1999). In budding yeast mitosis, loss of any one of these pathways does not severely disrupt chromosome biorientation, but may cause an increase in aneuploidy.…”