We report the development of a high-throughput screening platform to identify inhibitors of the membrane-bound A1Ao-ATP synthase from the rumen methanogen Methanobrevibacter ruminantium M1. Inhibitors identified in the screen were tested... more
We report the development of a high-throughput screening platform to identify inhibitors of the membrane-bound A1Ao-ATP synthase from the rumen methanogen Methanobrevibacter ruminantium M1. Inhibitors identified in the screen were tested against growing cultures of M. ruminantium, validating the approach to identify new inhibitors of methanogens.
The mitotic checkpoint protein Bub1 is essential for embryogenesis and survival of proliferating cells, and bidirectional deviations from its normal level of expression cause chromosome missegregation, aneuploidy, and cancer... more
The mitotic checkpoint protein Bub1 is essential for embryogenesis and survival of proliferating cells, and bidirectional deviations from its normal level of expression cause chromosome missegregation, aneuploidy, and cancer predisposition in mice. To provide insight into the physiological significance of this critical mitotic regulator at a modular level, we generated Bub1 mutant mice that lack kinase activity using a knockin gene-targeting approach that preserves normal protein abundance. In this paper, we uncover that Bub1 kinase activity integrates attachment error correction and mitotic checkpoint signaling by controlling the localization and activity of Aurora B kinase through phosphorylation of histone H2A at threonine 121. Strikingly, despite substantial chromosome segregation errors and aneuploidization, mice deficient for Bub1 kinase activity do not exhibit increased susceptibility to spontaneous or carcinogen-induced tumorigenesis. These findings provide a unique example of a modular mitotic activity orchestrating two distinct networks that safeguard against whole chromosome instability and reveal the differential importance of distinct aneuploidy-causing Bub1 defects in tumor suppression.
It is now clear that both centrioles and their surrounding pericentriolar material (PCM) are capable of self-assembly. Whereas centrioles are normally duplicated during G1-S phase, PCM components may be loaded onto centrosomes in both a... more
It is now clear that both centrioles and their surrounding pericentriolar material (PCM) are capable of self-assembly. Whereas centrioles are normally duplicated during G1-S phase, PCM components may be loaded onto centrosomes in both a microtubule-dependent and -independent manner at all stages of the cell cycle. Centrosomes enlarge dramatically after mitotic entry, when both Aurora A and Polo-like kinases cooperate to recruit additional gamma-tubulin ring complexes and microtubule-associated proteins to assist spindle formation.
The Aurora kinases play critical roles in the regulation of mitosis and are frequently overexpressed or amplified in human tumors. Selective inhibitors may provide a new therapy for the treatment of tumors with Aurora kinase... more
The Aurora kinases play critical roles in the regulation of mitosis and are frequently overexpressed or amplified in human tumors. Selective inhibitors may provide a new therapy for the treatment of tumors with Aurora kinase amplification. Herein we describe our lead optimization efforts within a 7-azaindole-based series culminating in the identification of GSK1070916 (17k). Key to the advancement of the series was the introduction of a 2-aryl group containing a basic amine onto the azaindole leading to significantly improved cellular activity. Compound 17k is a potent and selective ATP-competitive inhibitor of Aurora B and C with K(i)* values of 0.38 +/- 0.29 and 1.5 +/- 0.4 nM, respectively, and is >250-fold selective over Aurora A. Biochemical characterization revealed that compound 17k has an extremely slow dissociation half-life from Aurora B (>480 min), distinguishing it from clinical compounds 1 and 2. In vitro treatment of A549 human lung cancer cells with compound 17k...
Aurora kinases play a vital part in successful mitosis and cell division. Aberrant Aurora-A and -B expression is commonly seen in various types of tumors. Small molecule Aurora inhibitors have already entered clinical trials. Aurora-A... more
Aurora kinases play a vital part in successful mitosis and cell division. Aberrant Aurora-A and -B expression is commonly seen in various types of tumors. Small molecule Aurora inhibitors have already entered clinical trials. Aurora-A amplification has been shown to be associated with breast tumors from BRCA2-mutation carriers and such patients might therefore be candidates for treatment with Aurora kinase inhibitors. There is a need to identify markers that can predict sensitivity to Aurora inhibition. In this study sensitivity to the inhibitor ZM447439 was tested on a panel of 15 non-malignant and malignant epithelial cell lines that differed with respect to BRCA2 and p53 status and related to level of Aurora kinase expression. The IC(50) value for cell survival ranged from 1.9-8.1 μM and was not related to presence or absence of BRCA2 mutation. The levels of Aurora-A and -B expression correlated with each other but sensitivity towards ZM447439 did not correlate with levels of Aurora-A and -B mRNA expression, alone. Cells treated with the Aurora kinase inhibitor completed mitosis but cytokinesis was inhibited resulting in polyploidy and multinucleation. Different levels of polyploidy could not be fully explained by defects in p53. Only cell lines with a combination of high Aurora-A and -B expression, BRCA2 mutation and p53 defects showed more sensitivity towards Aurora inhibition than other cell lines. In conclusion, BRCA2-mutated cells showed variable sensitivity towards Aurora kinase inhibition. The level of sensitivity could not be predicted by Aurora expression levels alone but BRCA2 mutated tumors with high Aurora expression and non-functional p53 are likely candidates for treatment with Aurora inhibitors.
Aurora kinase inhibitors have attracted a great deal of interest as a new class of antimitotic agents. We report a novel class of Aurora inhibitors based on a pentacyclic scaffold. A prototype pentacyclic inhibitor 32 (AKI-001) derived... more
Aurora kinase inhibitors have attracted a great deal of interest as a new class of antimitotic agents. We report a novel class of Aurora inhibitors based on a pentacyclic scaffold. A prototype pentacyclic inhibitor 32 (AKI-001) derived from two early lead structures improves upon the best properties of each parent and compares favorably to a previously reported Aurora inhibitor, 39 (VX-680). The inhibitor exhibits low nanomolar potency against both Aurora A and Aurora B enzymes, excellent cellular potency (IC50 < 100 nM), and good oral bioavailability. Phenotypic cellular assays show that both Aurora A and Aurora B are inhibited at inhibitor concentrations sufficient to block proliferation. Importantly, the cellular activity translates to potent inhibition of tumor growth in vivo. An oral dose of 5 mg/kg QD is well tolerated and results in near stasis (92% TGI) in an HCT116 mouse xenograft model.
Breast cancer is a heterogeneous disease displaying some degree of familial clustering. Highly penetrant breast cancer susceptibility genes represent approximately 20-25% of the familial aggregation of breast cancer. A significant... more
Breast cancer is a heterogeneous disease displaying some degree of familial clustering. Highly penetrant breast cancer susceptibility genes represent approximately 20-25% of the familial aggregation of breast cancer. A significant proportion of this familial aggregation of breast cancer is thus yet to be explained by other breast cancer susceptibility genes. Given the high susceptibility conferred by the two major breast cancer predisposition genes, BRCA1 and BRCA2 and the implication of these genes in many key cellular processes, assessment of genes encoding BRCA1-interacting proteins as plausible breast cancer candidate genes is thus attractive. In this study, four genes encoding BRCA1-interacting proteins were analyzed in a cohort of 96 breast cancer individuals from high-risk non-BRCA1/BRCA2 French Canadian families. Although no deleterious truncating germline mutations or aberrant spliced mRNA species were identified, a total of 10, 4, 11 and 6 variants were found in the AURKA,...
Entamoeba histolytica is responsible for amoebiasis in humans. Its atypical cell cycle events and unique stress defense mechanisms make it different from other protozoan parasites. Comparative homology search identified seven homologs of... more
Entamoeba histolytica is responsible for amoebiasis in humans. Its atypical cell cycle events and unique stress defense mechanisms make it different from other protozoan parasites. Comparative homology search identified seven homologs of aurora kinases (EhAK1-7) in E. histolytica. Aurora kinases are well-known essential regulators of mitotic and meiotic cell division in eukaryotic organisms. EhAK6 contains a unique C-terminal endonuclease V domain, which is not reported in any other known aurora kinases. Endonuclease V domain-containing proteins are known to repair DNA in prokaryotes. Interestingly, we found that the mRNA expression of EhAK6 is increased upon UV-C irradiation in wild-type and also in the EhAK6 over-expressing transformants, in this primitive protozoan parasite. Several DNA repair proteins and EhSir2a, a Sir2 homolog known to be involved in regulating microtubular assembly were found to be the interactors of EhAK6 but not for the other aurora kinases in E. histolytica. We have predicted the theoretical model of EhAK6 and analyzed its interaction with the interactors by molecular docking. We propose that EhAK6, an aurora kinase homolog may be involved in DNA repair system in this human pathogen.
