This is probably due to increased microtubule mass in the metaphase spindle, owing to the formation of kinetochore fibers and their stabilization upon cyclin A destruction (Kabeche and Compton, 2013), which may underlie the Hec1-S55 phosphorylation on kinetochores at a distance from spindle poles. Chromosome oscillation facilitates Aurora ACdependent phosphorylation of Hec1-S55 during metaphase We addressed the relationship between chromosome oscillation and Hec1-S55 phosphorylation during metaphase, particularly whether chromosome oscillation promotes Hec1 phosphorylation. for efficient chromosome oscillation. Furthermore, enhancement of chromosome oscillation reduced the number of erroneous kinetochoreCmicrotubule attachments and chromosome missegregation, whereas inhibition of Aurora A during metaphase improved such errors. We propose that Aurora ACmediated metaphase Hec1-S55 phosphorylation through chromosome oscillation, together with Hec1-S69 phosphorylation, ensures mitotic fidelity by eliminating erroneous kinetochoreCmicrotubule attachments. Attenuated chromosome oscillation and the producing reduced Hec1-S55 phosphorylation may be a cause of CIN in malignancy cell lines. Graphical Abstract Open AR-M 1000390 hydrochloride in a separate window Introduction Most cancer cells have an abnormal quantity of chromosomes, known as aneuploidy (Ben-David and Amon, 2020; Weaver and Cleveland, 2006). Aneuploidy in malignancy cells usually results from chromosomal instability (CIN), a disorder in which chromosome missegregation happens at a high rate (Bakhoum and Compton, 2012a; Gordon et al., 2012; Tanaka and Hirota, 2016). Aneuploidy caused by CIN is generally disruptive to cellular fitness, but the resultant genetic heterogeneity is supposed to promote tumor formation and progression through clonal selection of any cells that acquire growth advantage. For proper chromosome segregation, kinetochores within the sister chromatids of replicated chromosomes must attach to microtubules from reverse spindle poles, referred to as amphitelic attachment or bi-orientation (Tanaka, 2013; Tanaka et al., 2005). The spindle assembly checkpoint (SAC) and the error correction mechanism guarantee bi-orientation establishment for those chromosomes: the SAC delays anaphase onset in the presence of unattached kinetochores, while Aurora kinases are involved in the correction of erroneous attachments, such as monotelic, syntelic, and merotelic attachment (Godek et al., 2015; Tanaka, 2002). Among these, merotelic attachment, in which a solitary kinetochore attaches to microtubules from both spindle poles, is not detected from the SAC and is thus considered as a main cause of CIN (Cimini, 2008). Conditions such as improved formation of merotelic attachment due to centrosome amplification AR-M 1000390 hydrochloride and reduced correction of merotelic attachment due to microtubule stabilization or reduced Aurora B activity have been proposed to induce CIN in malignancy cells (Holland and Cleveland, 2012; Tanaka and Hirota, 2016), even though underlying causes are not fully recognized. Correction of the erroneous kinetochoreCmicrotubule attachments LAMP2 by Aurora kinases is mainly performed by phosphorylation of Hec1, a component of the Ndc80 complex that is involved in the attachment of kinetochores to microtubules (DeLuca et al., 2006). It has been demonstrated that phosphorylation of the N-terminal tail of Hec1 reduces the affinity of the Ndc80 complex to microtubules and destabilizes kinetochoreCmicrotubule attachments, facilitating the error correction (Wimbish and DeLuca, 2020; Zaytsev et al., 2014). Aurora B, which is mainly recognized at inner centromere, plays a major part in the error correction (Cimini et al., 2006; Lampson and Cheeseman, 2011), whereas Aurora A, which resides within the spindle particularly in the poles, is known to phosphorylate Hec1 when chromosomes are near spindle poles (Chmtal et al., 2015; Ye et al., 2015). Interestingly, recent works have shown that Aurora A phosphorylates Hec1 at serine 69 (Hec1-S69) not only during prometaphase but also during metaphase, when chromosomes are aligned in the spindle equator distant from spindle poles (Bucko et al., 2019; DeLuca et al., 2018). During metaphase in mammalian cells, kinetochore pairs repeatedly move around the spindle equator, known as chromosome oscillation (Jaqaman et al., 2010; Skibbens et al., 1993; Wan et al., 2012), but the physiological tasks of such oscillation remain elusive. We found that chromosome oscillation is definitely attenuated in malignancy cell lines, and this is definitely correlated with reduced Hec1 phosphorylation at serine 55 (Hec1-S55) during metaphase. Furthermore, a portion of Aurora A residing in the spindle is mainly responsible for the metaphase Hec1-S55 phosphorylation. Intriguingly, the Hec1-S55 phosphorylation, together with phosphorylation at Hec1-S69, promotes chromosome oscillation and contributes to the correction of erroneous AR-M 1000390 hydrochloride kinetochoreCmicrotubule AR-M 1000390 hydrochloride attachments, therefore ensuring faithful chromosome segregation. Our data suggest that reduction of the metaphase Hec1-S55 phosphorylation by Aurora A due to attenuated chromosome oscillation is one of the causes of CIN in malignancy cell lines. Results Chromosome oscillation is definitely attenuated in malignancy cell lines First, we compared chromosome oscillation in human being retinal pigment epithelial (RPE-1) cells, a nontransformed cell collection, and the HeLa malignancy cell collection. When cells were caught in metaphase AR-M 1000390 hydrochloride by treatment with MG132, a proteasome inhibitor that prohibits progression from.
This is probably due to increased microtubule mass in the metaphase spindle, owing to the formation of kinetochore fibers and their stabilization upon cyclin A destruction (Kabeche and Compton, 2013), which may underlie the Hec1-S55 phosphorylation on kinetochores at a distance from spindle poles
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