Sds22 regulates aurora B activity and microtubule–kinetochore interactions at mitosis

SummaryIf uncorrected, merotelic kinetochore attachments can induce mis-segregated chromosomes in anaphase. We show that checkpoint kinase 1 (Chk1) protects vertebrate cells against merotelic attachments and lagging chromosomes and is required for correction of merotelic attachments during a prolonged metaphase. Decreased Chk1 activity leads to hyper-stable kinetochore microtubules, unstable binding of MCAK, Kif2b and Mps1 to centromeres or kinetochores and reduced phosphorylation of Hec1 by Aurora-B. Phosphorylation of Aurora-B at serine 331 (Ser331) by Chk1 is high in prometaphase and decreases significantly in metaphase cells. We propose that Ser331 phosphorylation is required for optimal localization of MCAK, Kif2b and Mps1 to centromeres or kinetochores and for Hec1 phosphorylation. Furthermore, inhibition of Mps1 activity diminishes initial recruitment of MCAK and Kif2b to centromeres or kinetochores, impairs Hec1 phosphorylation and exacerbates merotelic attachments in Chk1-deficient cells. We propose that Chk1 and Mps1 jointly regulate Aurora-B, MCAK, Kif2b and Hec1 to correct merotelic attachments. These results suggest a role for Chk1 and Mps1 in error correction.

Section: Chk1 Prevents Merotelic Attachments 1241supporting

confidence: 78%

Chk1 and Mps1 jointly regulate correction of merotelic kinetochore attachments

Petsalaki

Zachos

2013

“…Therefore, it has been proposed that B56-PP2A is directly responsible for K-fiber formation by reversing Aurora-B-mediated phosphorylation of the KMN network components. However, PP1 rather than PP2A has been shown to reverse phosphorylation on the kinetochore substrates of Aurora B, including the KMN network components (DeLuca et al, 2011;Lesage et al, 2011;Liu et al, 2010;Posch et al, 2010). Furthermore, it is possible that the increased phosphorylation of the KMN network components in B56-depleted cells might be secondary to the defect in promoting chromosome movement towards the metaphase plate.…”

Section: Introductionmentioning

confidence: 94%

“…Moreover, unlike directly disrupting the KMN network by depletion of NUF2 (Cai et al, 2009a), rescuing chromosome movement by co-depletion of HSET and B56 subunits was sufficient to restore both K-fiber formation and their function in mitotic exit. PP1, rather than PP2A, is thought to be the major phosphatase involved in directly stabilizing K-fibers, as PP1 has been shown to reverse phosphorylation on the kinetochore substrates of Aurora B, including the KMN network (DeLuca et al, 2011;Lesage et al, 2011;Liu et al, 2010;Posch et al, 2010). Notably, blocking KNL1-mediated recruitment of PP1 to the kinetochores markedly compromises the formation of cold-stable K-fibers, but not chromosome congression .…”

Section: Promoting Chromosome Movement In B56-depleted Cells Is Suffimentioning

confidence: 99%

B56-PP2A regulates motor dynamics for mitotic chromosome alignment

Virshup

Lee

2014

Proper alignment of duplicated chromosomes at the metaphase plate involves both motor-driven chromosome movement and the functional and physical end-on connection (K-fiber formation) between the kinetochore and the plus-end of microtubules. The B56 family of protein phosphatase 2A (PP2A) regulatory subunits (B56-PP2A), through their interaction with the mitotic checkpoint protein BUBR1, are required for proper chromosome alignment, but the underlying mechanism(s) has remained elusive. Here, we show that B56-PP2A promotes chromosome alignment primarily by balancing chromosome movement towards the metaphase plate, rather than by directly establishing stable K-fibers. Notably, the poleward movement of chromosomes in cells depleted of the B56 family can be rescued by depletion of HSET (also known as kinesin-14 or KIFC1), a major minus-end-directed motor protein. Strikingly, K-fiber formation can be restored if chromosome movement to the metaphase plate is rescued in B56-depleted cells. Furthermore, the B56-BUBR1 interaction is required for promoting motor-driven chromosome movement towards the metaphase plate. Thus, we propose that B56-PP2A functions in mitotic chromosome alignment by balancing chromosome movement towards the metaphase plate, which is essential for the subsequent establishment of stable and functional kinetochore-microtubule attachments, and mitotic exit.

“…(CDCA2) holoenzyme and the PP1-PPP1R7 (SDS22) holoenzyme (Posch et al, 2010;Vagnarelli et al, 2006).…”

Section: Journal Of Cell Sciencementioning

confidence: 99%

Protein phosphatases and the regulation of mitosis

Barr

Elliott

Grüneberg

2011

Catalytic mechanisms and inhibitor sensitivityPSTPs and PTPs use completely different catalytic mechanisms to dephosphorylate their substrates (Barford et al., 1998). Briefly, the PTPs share the conserved active site motif HCX 5 R, in which the essential catalytic cysteine acts as a nucleophile and forms an intermediate phospho-cysteine during hydrolysis (Barford et al., 1998;Fauman and Saper, 1996). By contrast, the phosphatases of Summary Dynamic control of protein phosphorylation is necessary for the regulation of many cellular processes, including mitosis and cytokinesis. Indeed, although the central role of protein kinases is widely appreciated and intensely studied, the importance of protein phosphatases is often overlooked. Recent studies, however, have highlighted the considerable role of protein phosphatases in both the spatial and temporal control of protein kinase activity, and the modulation of substrate phosphorylation. Here, we will focus on recent advances in our understanding of phosphatase structure, and the importance of phosphatase function in the control of mitotic spindle formation, chromosome architecture and cohesion, and cell division. ) and iron (Fe 2+ ), which are coordinated by a set of conserved amino acid residues (Shi, 2009). These bound metal ions coordinate the phosphate group of the substrate and stabilize the negative charge, thus facilitating nucleophilic attack on the phosphorus by a water molecule and hydrolysis of the phosphate ester bond (Goldberg et al., 1995). The catalytic subunits of the PPP family are so similar (Fig. 1A) that all family members are inhibited by the potent algal toxins microcystin-LR and okadaic acid (Fig. 1B), and share three substrate-peptide-binding grooves that lead to the catalytic site (Fig. 1C).Despite their similarity, the catalytic subunits of PPP family members PP1 and PP2A can be distinguished, to some extent, by their sensitivity to inhibition by okadaic acid. PP2A is inhibited by okadaic acid in the subnanomolar range [half-maximal inhibitory concentration (IC 50 )0.1 nM], whereas PP1 requires 100-fold higher concentrations of okadaic acid for inhibition . At a structural level, this can be explained by the absence of specific hydrophobic residues in the catalytic cleft of PP1 that are present in PP2A and are required for tight binding of the hydrophobic end of okadaic acid . However, although the catalytic subunits of PP1 and PP2A are highly active in isolation, and can be discriminated in terms of toxin sensitivity, they lack appreciable substrate specificity (Agostinis et al., 1992; Imaoka et al., 1983;Mumby et al., 1987). This close similarity and activity of their catalytic subunits are difficult to reconcile with their biological functions and specific substrates observed in cells. It is therefore unsurprising that these catalytic subunits associate with specific regulatory subunits that direct the biological activity of the PPP family phosphatases in living cells. As we will discuss later, this is necessary to explain how PP1...