Biology subjects

Kops, G. J.

Publications and source records attributed to Kops, G. J..

3 recordsLinked to original sources

bioRxiv2018

Interactions between N-terminal modules in MPS1 enable spindle checkpoint silencing

AO_SCPCAPBSTRACTC_SCPCAPFaithful chromosome segregation relies on the ability of the spindle assembly checkpoint (SAC) to delay anaphase onset until all chromosomes are attached to the mitotic spindle via their kinetochores. MPS1 kinase is recruited to unattached kinetochores to initiate SAC signaling, and is removed from kinetochores once stable microtubule attachments have been formed to allow normal mitotic progression. Here we show that a helical fragment within the kinetochore-targeting NTE module of MPS1 is required for interactions with kinetochores, and also forms intramolecular interactions with its adjacent TPR domain. Bypassing this NTE-TPR interaction results in high MPS1 levels at kinetochores due to loss of regulatory input into MPS1 localization, ineffecient MPS1 delocalization from kinetochores upon microtubule attachment, and SAC silencing defects. These results show that SAC responsiveness to attachments relies on regulated intramolecular interactions in MPS1 and highlight the sensitivity of mitosis to perturbations in the dynamics of the MSP1-NDC80-C interactions.

cell biology↗

bioRxiv2018

Dynamic Kinetochore Size Regulation Promotes Microtubule Capture And Chromosome Biorientation In Mitosis

Faithful chromosome segregation depends on the ability of sister kinetochores to attach to spindle microtubules. An outer layer of the kinetochore known as the fibrous corona transiently expands in early mitosis and disassembles upon microtubule capture. Neither the functional importance nor the mechanistic basis for this are known. Here we show that the dynein adaptor Spindly and the RZZ kinetochore complex drive fibrous corona formation in a dynein-independent manner. C-terminal farnesylation and MPS1 kinase activity cause conformational changes of Spindly that promote oligomerization of RZZ:Spindly complexes into a corona-like meshwork in cells and in vitro. Concurrent with corona expansion, Spindly potentiates corona shedding by recruiting dynein via three conserved short linear motifs. Expanded, non-sheddable fibrous coronas engage in extensive, long-lived lateral microtubule interactions that persist to metaphase and result in fused sister kinetochores, formation of merotelic attachments and chromosome segregation errors in anaphase. Thus, dynamic kinetochore size regulation in mitosis is coordinated by a single, Spindly-based mechanism that promotes initial microtubule capture and subsequent correct maturation of attachments.

cell biology↗

bioRxiv2016

Phylogenomics-guided discovery of a novel conserved cassette of short linear motifs in BubR1 essential for the spindle checkpoint

The spindle assembly checkpoint (SAC) maintains genomic integrity by preventing progression of mitotic cell division until all chromosomes are stably attached to spindle microtubules. The SAC critically relies on the paralogs Bub1 and BubR1/Mad3, which integrate kinetochore-spindle attachment status with generation of the anaphase inhibitory complex MCC. We previously reported on the widespread occurrences of independent gene duplications of an ancestral MadBub gene in eukaryotic evolution and the striking parallel subfunctionalization that lead to loss of kinase function in BubR1/Mad3-like paralogs. We now present an elaborate subfunctionalization analysis that includes all known motifs in Bub1 and BubR1, and show that ancestral features are consistently retained in the same functional paralog: GLEBS/CDI/CDII/kinase in the Bub1-like and KEN1/KEN2/D-Box in the BubR1/Mad3-like. The recently described ABBA motif can be found in either or both paralogs. We however discovered two additional ABBA motifs that flank KEN2. This cassette of ABBA1-KEN2-ABBA2 forms a strictly conserved module in all ancestral and BubR1/Mad3-like proteins, suggestive of a specific and crucial SAC function. Indeed, deletion of the ABBA motifs in human BUBR1 abrogates the SAC and affects APC/C-Cdc20 interactions. Our detailed comparative genomics analyses thus enabled discovery of a conserved cassette of motifs essential for the SAC and shows how this approach can be used to uncover hitherto unrecognized functional protein features.

cell biology↗