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Evidence that Aurora B is implicated in spindle checkpoint signalling independently of error correction.

Santaguida S, Vernieri C, Villa F, Ciliberto A, Musacchio A - EMBO J. (2011)

Bottom Line: Here, we report an analysis of the role of Aurora B in the spindle checkpoint under conditions believed to uncouple the effects of Aurora B inhibition on the checkpoint from those on error correction.Thus, Aurora B might contribute to spindle checkpoint signalling independently of error correction.Our results support a model in which Aurora B is at the apex of a signalling pyramid whose sensory apparatus promotes the concomitant activation of error correction and checkpoint signalling pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Oncology, European Institute of Oncology, Milan, Italy.

ABSTRACT
Fidelity of chromosome segregation is ensured by a tension-dependent error correction system that prevents stabilization of incorrect chromosome-microtubule attachments. Unattached or incorrectly attached chromosomes also activate the spindle assembly checkpoint, thus delaying mitotic exit until all chromosomes are bioriented. The Aurora B kinase is widely recognized as a component of error correction. Conversely, its role in the checkpoint is controversial. Here, we report an analysis of the role of Aurora B in the spindle checkpoint under conditions believed to uncouple the effects of Aurora B inhibition on the checkpoint from those on error correction. Partial inhibition of several checkpoint and kinetochore components, including Mps1 and Ndc80, strongly synergizes with inhibition of Aurora B activity and dramatically affects the ability of cells to arrest in mitosis in the presence of spindle poisons. Thus, Aurora B might contribute to spindle checkpoint signalling independently of error correction. Our results support a model in which Aurora B is at the apex of a signalling pyramid whose sensory apparatus promotes the concomitant activation of error correction and checkpoint signalling pathways.

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Synergistic effects from inhibiting Aurora B and other checkpoint and kinetochore proteins. (A) HeLa cells were depleted of Nuf2 (a subunit of the Ndc80 complex), Mps1 or Aurora B by RNAi. Depletion of Nuf2 also destabilizes the Ndc80 subunit of the complex (Meraldi et al, 2004). (B, C) HeLa cells were released from a double thymidine arrest and treated with 3.3 μM nocodazole and the indicated inhibitors in combination with the indicated RNAi-based depletions. Cells were analysed by time-lapse video microscopy. Time spent in mitosis was evaluated based on mitotic rounding up of cells. Values represent mean and s.d. and were calculated from at least 50 cells for each condition.
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f6: Synergistic effects from inhibiting Aurora B and other checkpoint and kinetochore proteins. (A) HeLa cells were depleted of Nuf2 (a subunit of the Ndc80 complex), Mps1 or Aurora B by RNAi. Depletion of Nuf2 also destabilizes the Ndc80 subunit of the complex (Meraldi et al, 2004). (B, C) HeLa cells were released from a double thymidine arrest and treated with 3.3 μM nocodazole and the indicated inhibitors in combination with the indicated RNAi-based depletions. Cells were analysed by time-lapse video microscopy. Time spent in mitosis was evaluated based on mitotic rounding up of cells. Values represent mean and s.d. and were calculated from at least 50 cells for each condition.

Mentions: Results so far indicate that hesperadin has negative consequences on the checkpoint even when microtubules have been completely depolymerized to exclude effects from inhibiting error correction. Thus, our results challenge the contention that Aurora B influences the checkpoint exclusively through error correction (Yang et al, 2009). We note that this contention was based on the undemonstrated assumption that 100 nM hesperadin is sufficient to completely abrogate Aurora B activity, but our results on the duration of the mitotic arrest at different doses of hesperadin (Supplementary Table SI; Figure 2B) suggest that this might not be the case. This issue is further addressed in experiments presented in Figures 4, 5 and 6.


Evidence that Aurora B is implicated in spindle checkpoint signalling independently of error correction.

Santaguida S, Vernieri C, Villa F, Ciliberto A, Musacchio A - EMBO J. (2011)

Synergistic effects from inhibiting Aurora B and other checkpoint and kinetochore proteins. (A) HeLa cells were depleted of Nuf2 (a subunit of the Ndc80 complex), Mps1 or Aurora B by RNAi. Depletion of Nuf2 also destabilizes the Ndc80 subunit of the complex (Meraldi et al, 2004). (B, C) HeLa cells were released from a double thymidine arrest and treated with 3.3 μM nocodazole and the indicated inhibitors in combination with the indicated RNAi-based depletions. Cells were analysed by time-lapse video microscopy. Time spent in mitosis was evaluated based on mitotic rounding up of cells. Values represent mean and s.d. and were calculated from at least 50 cells for each condition.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3102279&req=5

f6: Synergistic effects from inhibiting Aurora B and other checkpoint and kinetochore proteins. (A) HeLa cells were depleted of Nuf2 (a subunit of the Ndc80 complex), Mps1 or Aurora B by RNAi. Depletion of Nuf2 also destabilizes the Ndc80 subunit of the complex (Meraldi et al, 2004). (B, C) HeLa cells were released from a double thymidine arrest and treated with 3.3 μM nocodazole and the indicated inhibitors in combination with the indicated RNAi-based depletions. Cells were analysed by time-lapse video microscopy. Time spent in mitosis was evaluated based on mitotic rounding up of cells. Values represent mean and s.d. and were calculated from at least 50 cells for each condition.
Mentions: Results so far indicate that hesperadin has negative consequences on the checkpoint even when microtubules have been completely depolymerized to exclude effects from inhibiting error correction. Thus, our results challenge the contention that Aurora B influences the checkpoint exclusively through error correction (Yang et al, 2009). We note that this contention was based on the undemonstrated assumption that 100 nM hesperadin is sufficient to completely abrogate Aurora B activity, but our results on the duration of the mitotic arrest at different doses of hesperadin (Supplementary Table SI; Figure 2B) suggest that this might not be the case. This issue is further addressed in experiments presented in Figures 4, 5 and 6.

Bottom Line: Here, we report an analysis of the role of Aurora B in the spindle checkpoint under conditions believed to uncouple the effects of Aurora B inhibition on the checkpoint from those on error correction.Thus, Aurora B might contribute to spindle checkpoint signalling independently of error correction.Our results support a model in which Aurora B is at the apex of a signalling pyramid whose sensory apparatus promotes the concomitant activation of error correction and checkpoint signalling pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Oncology, European Institute of Oncology, Milan, Italy.

ABSTRACT
Fidelity of chromosome segregation is ensured by a tension-dependent error correction system that prevents stabilization of incorrect chromosome-microtubule attachments. Unattached or incorrectly attached chromosomes also activate the spindle assembly checkpoint, thus delaying mitotic exit until all chromosomes are bioriented. The Aurora B kinase is widely recognized as a component of error correction. Conversely, its role in the checkpoint is controversial. Here, we report an analysis of the role of Aurora B in the spindle checkpoint under conditions believed to uncouple the effects of Aurora B inhibition on the checkpoint from those on error correction. Partial inhibition of several checkpoint and kinetochore components, including Mps1 and Ndc80, strongly synergizes with inhibition of Aurora B activity and dramatically affects the ability of cells to arrest in mitosis in the presence of spindle poisons. Thus, Aurora B might contribute to spindle checkpoint signalling independently of error correction. Our results support a model in which Aurora B is at the apex of a signalling pyramid whose sensory apparatus promotes the concomitant activation of error correction and checkpoint signalling pathways.

Show MeSH