BUBR1 Pseudokinase Domain Promotes Kinetochore PP2A-B56 Recruitment, Spindle Checkpoint Silencing, and Chromosome Alignment

Abstract

Highlights d BUBR1 KARD and pseudokinase domains often co-present in vertebrates d BUBR1 pseudokinase is necessary for KARD phosphorylation and PP2A-B56 recruitment d The pseudokinase regulates SAC exit and chromosome alignment via PP2A-B56 d BUB1 kinase activity is required for optimal BUBR1 KARD phosphorylation

There’s more to death than life: Noncatalytic functions in kinase and pseudokinase signaling

“…Moreover, there are divergent reports of nucleotide binding and activity by the Drosophila protein, compared with human BUBR1 ( 9 , 70 ). Coevolution analyses suggest that a phosphorylation-dependent phosphatase docking site (known as a KARD motif) has been positively selected in conjunction with the BUBR1 pseudokinase domains ( 71 ). Mutational studies revealed that residues within the pseudoactive site of the BUBR1 pseudokinase domain, but not catalysis itself, are essential to the ability of BUBR1 to regulate KARD phosphorylation and scaffold assembly ( 71 ).…”

“…Coevolution analyses suggest that a phosphorylation-dependent phosphatase docking site (known as a KARD motif) has been positively selected in conjunction with the BUBR1 pseudokinase domains ( 71 ). Mutational studies revealed that residues within the pseudoactive site of the BUBR1 pseudokinase domain, but not catalysis itself, are essential to the ability of BUBR1 to regulate KARD phosphorylation and scaffold assembly ( 71 ). Phosphorylation of the KARD motif in BUBR1 was essential as part of a phosphorylation relay, because it then facilitates scaffolding of an active complex with PP2A.…”

“…Phosphorylation of the KARD motif in BUBR1 was essential as part of a phosphorylation relay, because it then facilitates scaffolding of an active complex with PP2A. The posited model proposes that an intramolecular interaction between the pseudokinase and KARD motifs promotes phosphorylation, potentially by stabilizing the KARD region ( 71 ). Such a model will be an intriguing to examine further, given the key role of BUBR1 in checkpoint silencing and mitotic exit.…”

Bub1 and CENP-U redundantly recruit Plk1 to stabilize kinetochore-microtubule attachments and ensure accurate chromosome segregation

“…Our data support a model in which parallel recruitment of Plk1 to kinetochores by CENP-U and Bub1 stabilizes KT-MT attachment, thereby ensuring proper chromosome alignment and segregation (Figure 7I). Our observations further suggest that Bub1 may also play a Plk1 recruitment-independent role in chromosome alignment under normal conditions, possibly through promoting the kinetochore localization of BubR1 in complex with protein phosphatase 2A (PP2A) that stabilizes KT-MT attachment (Gama Braga et al, 2020;Hayward et al, 2019;Kruse et al, 2013;Suijkerbuijk et al, 2012;Vallardi et al, 2019;Xu et al, 2013). A number of proteins, including Bub1 (Qi et al, 2006), CENP-U (Kang et al, 2006), BubR1 (Elowe et al, 2007;Matsumura et al, 2007), the CPC (Goto et al, 2006;Sun et al, 2012), NCAPG2 (Kim et al, 2014), CLASP2 (Maia et al, 2012), RSF1 (Lee et al, 2018), USP16 (Zhuo et al, 2015), Sgo1 (Pouwels et al, 2007), Dynactin (Yeh et al, 2013), NudC (Nishino et al, 2006), and CLIP-170 (Amin et al, 2014), are reported to be Plk1 receptors at the centromere/kinetochore.…”

A bifunctional kinase-phosphatase module integrates mitotic checkpoint and error-correction signalling to ensure mitotic fidelity

“…To create the phosphatase-dominant situation, B56γ was tethered to the C-terminus of BUBR1 in place of the KARD and pseudokinase domain (BUBR1 B56γ ). Note, that the only known function of the pseudokinase is to regulate KARD phosphorylation and therefore PP2A-B56 recruitment (Gama Braga et al , 2020). To create the analogous kinase-dominant situation, that KARD was deleted together with the pseudokinase domain by removing the entire C-terminus (BUBR1 ΔPP2A(ΔC) ).…”