The molecular mechanisms that ensure accurate chromosome segregation in mitosis and meiosis are of fundamental importance to the conservation of euploidy in eukaryotes. Errors in this process (e.g., chromosome nondisjunction and chromosome loss) result in aneuploidy—the phenotypic consequences of which are usually profound, including cancer, birth defects, and developmental disorders such as Down syndrome. In humans, errors in chromosome segregation may trigger the onset of neoplasia by uncovering the expression of recessive oncogenic phenotypes, or by contributing to the development of specific aneuploidies. The centromere, a single locus per chromosome, is essential to ensure high fidelity of chromosome transmission. The kinetochore (the protein complex at the centromere) mediates attachment of chromosomes to spindle microtubules and directs chromosome movement during mitosis. Cells have a surveillance system, the spindle checkpoint, which can delay mitotic progression by transiently inhibiting the anaphase-promoting complex in response to defective kinetochore-microtubule attachment. Defects in kinetochore function and the spindle checkpoint result in aneuploidy. Considerable evidence indicates a role of a dysfunctional spindle checkpoint in tumorigenesis.
In most eukaryotes, the centromere is associated with large arrays of repetitive DNA, but has no defined DNA sequence. Consequently, heritability of the centromere is thought to involve epigenetic modifications. CENP-A, the centromeric histone H3 variant, is thought to be a strong candidate for the epigenetic mark. After DNA replication, centromeric nucleosomes, including existing CENP-A, are distributed to the replicated chromatids, and newly synthesized CENP-A deposition occurs at the centromere in G1 in humans. This regulation is crucial for proper centromere inheritance and function. One of our goals is to determine the function of post-translational modifications (PTMs) of CENP-A in the regulation of CENP-A deposition at the centromere and the assembly of kinetochore complexes.
Neocentromeres originate from non-centromeric regions of chromosomes, (i.e., not alpha-satellite DNA). The formation of complex rearranged chromosomes, each containing a neocentromere, has been observed in cancer cells, particularly hematological malignancies. Addition of a neocentromere to a chromosome with an endogenous centromere creates a dicentric state, which results in extensive genomic instability displaying hallmarks of cellular transformation. In colon cancer, CENP-A is overexpressed, and this overexpression is associated with mistargeting of CENP-A to non-centromeric chromatin. These findings suggest that overexpression of CENP-A might cause aneuploidy by creating neocentromeres. In addition, genomic amplification of the CENP-A locus occurred in neuroendocrine prostate cancer (15% of cases) and breast cancer (10% of cases).
Thus, elucidating the mechanism of neocentromere formation will contribute to understanding the mechanism of “cancer evolution” that results in resistance to cancer therapy.
Niikura Y, Kitagawa R and Kitagawa K. CENP-A Ubiquitylation is the epigenetic mark for centromere identify. Cell Reports 2016, 15: 61-76.
Niikura Y andKitagawa K. Immunofluorescence analysis of endogenous and exogenous centromere-kinetochore proteins. J Vis Exp. 2016 Mar 3;(109). doi: 10.3791/53732.
Ogi H, Sakuraba Y, Kitagawa R, Xiao L, Shen C, Cynthia M, Ohta S, Arnold MA, Ramirez N, Houghton PJ, and Kitagawa K. The Oncogenic Role of the Cochaperone Sgt1. Oncogenesis 2015 2015 May 18;4:e149.
Niikura Y, Kitagawa R, Ogi H, Abdulle R, Pagala V, and Kitagawa K. CENP-A K124 Ubiquitylation Is Required for CENP-A Deposition at the Centromere. Developmental Cell 2015 Mar 9;32(5):589-603.
Ohkuni K, Abdulle R, and Kitagawa K. Degradation of centromeric histone H3 variant Cse4 requires the Fpr3 peptidyl-prolyl cis-trans isomerase. Genetics 2014; 196(4):1041-5.
Bian Y, Kitagawa R, Bansal PK, Fujii Yo, Stepanov A, and Kitagawa K. Synthetic genetic array screen identifies PP2A as a therapeutic target in Mad2-overexpressing tumors. Proc Natl Acad Sci U S A. 2014; 111(4):1628-33
Kikuchi K, Narita T, Pham VT, Iijima J, Hirota K, Keka IS, Mohiuddin M, Okawa K, Hori T, Fukagawa T, Essers J, Kanaar R, Whitby MC, Sugasawa K, Taniguchi Y, Kitagawa K, Takeda S. Structure-specific endonucleases Xpf and Mus81 play overlapping but essential roles in DNA repair by homologous recombination. Cancer Res. 2013; 73(14):4362-71
Ohkuni K and Kitagawa K, Role of transcription at centromeres in budding yeast. Transcription 2012; 3(4).
Ohkuni K and Kitagawa K, Endogenous Transcription at the Centromere Facilitates Centromere Activity in Budding Yeast. Current Biology 2011; 21(20):1695-703.
Yang C, Tang X, Guo X, Niikura Y, Kitagawa K, Cui K, Wong STC, Fu L, and Xu B, Aurora-B Mediated ATM Serine 1403 Phosphorylation Is Required For Mitotic ATM Activation and the Spindle Checkpoint. Molecular Cell 2011; 44(4):597-608.
Kitagawa K, Too early to say, "no targeting of mitosis!" Nat Rev Clin Oncol. 2011; 8(7):444.
Goto GH, Mishra A, Abdulle R, Slaughter CA, and Kitagawa K, Bub1-mediated Adaptation of the Spindle Checkpoint. PLoS Genetics 2011; 7(1):e1001282.
Kikuchi K, Niikura Y, Kitagawa K, and Kikuchi A, Dishevelled, a Wnt signaling component, is involved in mitotic progression in cooperation with Plk1. EMBO J. 2010; 29(20):3470-83.
Niikura Y, Ogi H, Kikuchi K, Kitagawa K, BUB3 that dissociates from BUB1 activates caspase-independent mitotic death (CIMD). Cell Death Differ. 2010; 17(6):1011-24.
Bansal PK, Mishra A, High AA, Abdulle R, Kitagawa K, Sgt1 dimerization is negatively regulated by protein kinase CK2-mediated phosphorylation at S361; J Biol Chem. 2009; 284(28):18692-8.
Bansal PK, Nourse A, Abdulle R, Kitagawa K. Sgt1 dimerization is required for yeast kinetochore assembly. J Biol Chem. 2009; 284(6):3586-92.
Kitagawa K* and Niikura Y. Caspase-Independent Mitotic Death (CIMD). Cell Cycle. 2008; 7(8):1001-5.
Ohkuni K, Abdulle R, Tong AH, Boone C, and Kitagawa K. Ybp2 Associates with the Central Kinetochore of Saccharomyces cerevisiae and Mediates Proper Mitotic Progression. PLoS ONE. 2008;3(2):e1617.
Niikura Y, Dixit A, Scott R, Perkins G and Kitagawa K. BUB1 mediation of caspase-independent mitotic death determines cell fate. J. Cell Biol. 2007;178(2):283-96. (Faculty of 1000 Biology: F1000 Factor 6.0: Must Read http://www.f1000biology.com/article/id/1088744/eva....
Scaglione KM, Bansal PK, Deffenbaugh AE, Kiss A, Moore JM, Korolev S, Cocklin R, Goebl M, Kitagawa K, and Skowyra D. SCF E3 -mediated autoubiquitination negatively regulates activity of the Cdc34 E2 but plays a nonessential role in the catalytic cycle in vitro and in vivo. Mol. Cell. Biol. 2007;27(16):5860-70.
Niikura Y, Ohta S, Vandenbeldt KJ, Abdulle R, McEwen BF and Kitagawa K. 17-AAG, an Hsp90 inhibitor, causes kinetochore defects: a novel mechanism by which 17-AAG inhibits cell proliferation. Oncogene 2006; 25:4133-46 (Faculty of 1000 Biology: F1000 Factor 3.0: Recommended http://www.f1000biology.com/article/id/1033229/eva....
Kondo-Okamoto N, Ohkuni K, Kitagawa K, McCaffery JM, Shaw JM, Okamoto K. The novel F-box protein Mfb1p regulates mitochondrial connectivity and exhibits asymmetric localization in yeast. Mol. Biol. Cell 2006; 17:3756-67.
Bansal PK, Abdulle R, and Kitagawa K. Sgt1 associates with molecular chaperones: an initial step of assembly of the core kinetochore complex. Mol. Cell. Biol. 2004 Sep;24(18):8069-79.
Steensgaard P, Garre M, Muradore I, Transidico P, Nigg EA, Kitagawa K, Earnshaw WC, Faretta M, Musacchio A. Sgt1 is required for human kinetochore assembly. EMBO Rep. 2004 Jun;5(6):626-31. Epub 2004 May 07.
Niikura Y and Kitagawa K. Identification of a Novel Splice Variant: Human SGT1B (SUGT1B). DNA sequence. 2003 Dec;14(6):436-41.
Kitagawa K, Abdulle R, Bansal PK, Cagney G, Fields S, and Hieter P. Requirement of Skp1-Bub1 interaction for kinetochore-mediated activation of the spindle checkpoint. Mol. Cell. 2003 May;11(5):1201-13.
Nowotny M, Spiechowicz M, Jastrzebska B, Filipek A, Kitagawa K, Kuznicki J. Calcium-regulated interaction of Sgt1 with S100A6 (calcyclin) and other S100 proteins. J. Biol. Chem. 2003 Jul 18;278(29):26923-8. Epub 2003 May 13.
Kitagawa K and Abdulle R. In vivo site-directed mutagenesis of yeast plasmids by using a three-fragment homologous recombination system. Biotechniques. 2002 Aug;33(2):288, 290, 292 passim.
Schadick KH, Fourcade M, Boumenot P, Seitz JJ, Morrell JL, Chang L, Gould KL, Partridge JF, Allshire RC, Kitagawa K, Hieter P, and Hoffman CS.* Schizosaccharomyces pombe Git7p, a member of the Saccharomyces cerevisiae Sgt1p family, is required for Pglucose/cAMP signaling, cell wall integrity, and septation. Eukaryot Cell. 2002 Aug;1 (4):558-67.
Dubacq C, Guerois R, Courbeyrette R, Kitagawa K, and Mann C. Sgt1p contributes to cAMP pathway activity and physically interacts with the adenylyl cyclase Cyr1p/Cdc35p in budding yeast. Eukaryot Cell. 2002 Aug;1 (4):568-82.