Probing the catalytic functions of Bub1 kinase using the small molecule inhibitors BAY-320 and BAY-524

Abstract

The kinase Bub1 functions in the spindle assembly checkpoint (SAC) and in chromosome congression, but the role of its catalytic activity remains controversial. Here, we use two novel Bub1 inhibitors, BAY-320 and BAY-524, to demonstrate potent Bub1 kinase inhibition both in vitro and in intact cells. Then, we compared the cellular phenotypes of Bub1 kinase inhibition in HeLa and RPE1 cells with those of protein depletion, indicative of catalytic or scaffolding functions, respectively. Bub1 inhibition affected chromosome association of Shugoshin and the chromosomal passenger complex (CPC), without abolishing global Aurora B function. Consequently, inhibition of Bub1 kinase impaired chromosome arm resolution but exerted only minor effects on mitotic progression or SAC function. Importantly, BAY-320 and BAY-524 treatment sensitized cells to low doses of Paclitaxel, impairing both chromosome segregation and cell proliferation. These findings are relevant to our understanding of Bub1 kinase function and the prospects of targeting Bub1 for therapeutic applications.DOI: http://dx.doi.org/10.7554/eLife.12187.001

Chromosomal instability: A common feature and a therapeutic target of cancer

“…Extremely shortened mitosis induces massive chromosome missegregation and/or tetraploidization that elevates cell stress beyond the lethal level [164,165]. In line with the idea, inhibitors of Mps1 kinase were shown to exert anti-tumor activities [166][167][168], and anti-SAC compounds were reported to sensitize cancer cells to microtubule-targeting drugs [169][170][171][172].…”

Phylogenomics-guided discovery of a novel conserved cassette of short linear motifs in BubR1 essential for the spindle checkpoint

“…We performed iterated sensitive homology searches with jackhammer (Finn et al, 2011) (based on the TPR, kinase, CDI, GLEBS and KEN boxes) using a permissive E-value and bitscore cut-off to include diverged homologs on uniprot release 2016_08 and Ensemble Genomes 32 (http://www.ebi.ac.uk/Tools/hmmer/search/jackhmmer). Incompletely predicted genes were searched against whole genome shotgun contigs (wgs, http://www.ncbi.nlm.nih.gov/genbank/wgs) using tblastn.…”

Defects in centromeric/pericentromeric histone H2A T120 phosphorylation by hBUB1 cause chromosome missegregation producing multinucleated cells

“…It was shown that Bub1 phosphorylates the conserved histone H2A serine 121, which corresponds to H2A threonine 120 in humans. The histone H2A S121A mutant, in which all cellular H2A serine 121 is replaced by alanine, mimics the Bub1 kinase-dead mutant (Bub1-KD) in perturbing the centromeric localization of the Shugoshin protein, which is also associated with the pericentromeric chromosomal region and plays multiple roles in ensuring the accuracy of chromosome segregation during both mitosis and meiosis (Asghar et al, 2015;Baron et al, 2016;Lin, Jia, Tomchick, Luo, & Yu, 2014;Liu, Jia, & Yu, 2013;Liu et al, 2015;Marston, 2015). In addition to its role in histone H2A phosphorylation, it has also been reported that over-expression of Bub1 drives chromosomal instability through hyperactivation of Aurora B kinase (Ricke, Jeganathan, & van Deursen, 2011).…”