Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

MAD1: Kinetochore Receptors and Catalytic Mechanisms.

ABSTRACT: The mitotic checkpoint monitors kinetochore-microtubule attachment, delays anaphase onset and prevents aneuploidy when unattached or tensionless kinetochores are present in cells. Mitotic arrest deficiency 1 (MAD1) is one of the evolutionarily conserved core mitotic checkpoint proteins. MAD1 forms a cell cycle independent complex with MAD2 through its MAD2 interaction motif (MIM) in the middle region. Such a complex is enriched at unattached kinetochores and functions as an unusual catalyst to promote conformational change of additional MAD2 molecules, constituting a crucial signal amplifying mechanism for the mitotic checkpoint. Only MAD2 in its active conformation can be assembled with BUBR1 and CDC20 to form the Mitotic Checkpoint Complex (MCC), which is a potent inhibitor of anaphase onset. Recent research has shed light on how MAD1 is recruited to unattached kinetochores, and how it carries out its catalytic activity. Here we review these advances and discuss their implications for future research.

SUBMITTER: Luo Y

PROVIDER: S-EPMC5949338 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

MAD1: Kinetochore Receptors and Catalytic Mechanisms.

Luo Yibo Y Ahmad Ejaz E Liu Song-Tao ST

Frontiers in cell and developmental biology 20180507

The mitotic checkpoint monitors kinetochore-microtubule attachment, delays anaphase onset and prevents aneuploidy when unattached or tensionless kinetochores are present in cells. Mitotic arrest deficiency 1 (MAD1) is one of the evolutionarily conserved core mitotic checkpoint proteins. MAD1 forms a cell cycle independent complex with MAD2 through its MAD2 interaction motif (MIM) in the middle region. Such a complex is enriched at unattached kinetochores and functions as an unusual catalyst to p ...[more]

PMID: 29868582

Similar Datasets

Molecular mechanism of Mad1 kinetochore targeting by phosphorylated Bub1.

Project description:During metaphase, in response to improper kinetochore-microtubule attachments, the spindle assembly checkpoint (SAC) activates the mitotic checkpoint complex (MCC), an inhibitor of the anaphase-promoting complex/cyclosome (APC/C). This process is orchestrated by the kinase Mps1, which initiates the assembly of the MCC onto kinetochores through a sequential phosphorylation-dependent signalling cascade. The Mad1-Mad2 complex, which is required to catalyse MCC formation, is targeted to kinetochores through a direct interaction with the phosphorylated conserved domain 1 (CD1) of Bub1. Here, we present the crystal structure of the C-terminal domain of Mad1 (Mad1CTD ) bound to two phosphorylated Bub1CD1 peptides at 1.75 Å resolution. This interaction is mediated by phosphorylated Bub1 Thr461, which not only directly interacts with Arg617 of the Mad1 RLK (Arg-Leu-Lys) motif, but also directly acts as an N-terminal cap to the CD1 α-helix dipole. Surprisingly, only one Bub1CD1 peptide binds to the Mad1 homodimer in solution. We suggest that this stoichiometry is due to inherent asymmetry in the coiled-coil of Mad1CTD and has implications for how the Mad1-Bub1 complex at kinetochores promotes efficient MCC assembly.

| S-EPMC8391104 | biostudies-literature

Cep57 is a Mis12-interacting kinetochore protein involved in kinetochore targeting of Mad1-Mad2.

Project description:The spindle assembly checkpoint (SAC) arrests cells in mitosis by sensing unattached kinetochores, until all chromosomes are bi-oriented by spindle microtubules. Kinetochore accumulation of the SAC component Mad1-Mad2 is crucial for SAC activation. However, the mechanism by which Mad1-Mad2 accumulation at kinetochores is regulated is not clear. Here we find that Cep57 is localized to kinetochores in human cells, and binds to Mis12, a KMN (KNL1/Mis12 complex/Ndc80 complex) network component. Cep57 also interacts with Mad1, and depletion of Cep57 results in decreased kinetochore localization of Mad1-Mad2, reduced SAC signalling and increased chromosome segregation errors. We also show that the microtubule-binding activity of Cep57 is involved in the timely removal of Mad1 from kinetochores. Thus, these findings reveal that the KMN network-binding protein Cep57 is a mitotic kinetochore component, and demonstrate the functional connection between the KMN network and the SAC.

| S-EPMC4729865 | biostudies-other

Cyclin B1 scaffolds MAD1 at the kinetochore corona to activate the mitotic checkpoint.

Project description:Cyclin B:CDK1 is the master kinase regulator of mitosis. We show here that, in addition to its kinase functions, mammalian Cyclin B also scaffolds a localised signalling pathway to help preserve genome stability. Cyclin B1 localises to an expanded region of the outer kinetochore, known as the corona, where it scaffolds the spindle assembly checkpoint (SAC) machinery by binding directly to MAD1. In vitro reconstitutions map the key binding interface to a few acidic residues in the N-terminal region of MAD1, and point mutations in this sequence abolish MAD1 corona localisation and weaken the SAC. Therefore, Cyclin B1 is the long-sought-after scaffold that links MAD1 to the corona, and this specific pool of MAD1 is needed to generate a robust SAC response. Robustness arises because Cyclin B1:MAD1 localisation loses dependence on MPS1 kinase after the corona has been established, ensuring that corona-localised MAD1 can still be phosphorylated when MPS1 activity is low. Therefore, this study explains how corona-MAD1 generates a robust SAC signal, and it reveals a scaffolding role for the key mitotic kinase, Cyclin B1:CDK1, which ultimately helps to inhibit its own degradation.

| S-EPMC7298293 | biostudies-literature

Structure of human Mad1 C-terminal domain reveals its involvement in kinetochore targeting.

Project description:The spindle checkpoint prevents aneuploidy by delaying anaphase onset until all sister chromatids achieve proper microtubule attachment. The kinetochore-bound checkpoint protein complex Mad1-Mad2 promotes the conformational activation of Mad2 and serves as a catalytic engine of checkpoint signaling. How Mad1 is targeted to kinetochores is not understood. Here, we report the crystal structure of the conserved C-terminal domain (CTD) of human Mad1. Mad1 CTD forms a homodimer and, unexpectedly, has a fold similar to those of the kinetochore-binding domains of Spc25 and Csm1. Nonoverlapping Mad1 fragments retain detectable kinetochore targeting. Deletion of the CTD diminishes, does not abolish, Mad1 kinetochore localization. Mutagenesis studies further map the functional interface of Mad1 CTD in kinetochore targeting and implicate Bub1 as its receptor. Our results indicate that CTD is a part of an extensive kinetochore-binding interface of Mad1, and rationalize graded kinetochore targeting of Mad1 during checkpoint signaling.

| S-EPMC3340083 | biostudies-literature

Control of the spindle checkpoint by lateral kinetochore attachment and limited Mad1 recruitment.

Project description:We observed the dynamic recruitment of spindle checkpoint proteins Mad1 and Bub1 to detached kinetochores in budding yeast using real-time live-cell imaging and quantified recruitment in fixed cells. After induced de novo kinetochore assembly at one pair of sister centromeres, Mad1 appeared after the kinetochore protein Mtw1. Detached kinetochores were not associated with the nuclear envelope, so Mad1 does not anchor them to nuclear pore complexes (NPCs). Disrupting Mad1's NPC localization increased Mad1 recruitment to detached sister kinetochores. Conversely, increasing the number of detached kinetochores reduced the amount of Mad1 per detached kinetochore. Bub1 also relocalized completely from the spindle to detached sister centromeres after kinetochore assembly. After their capture by microtubules, Mad1 and Bub1 progressively disappeared from kinetochores. Sister chromatids that arrested with a lateral attachment to one microtubule exhibited half the Mad1 of fully detached sisters. We propose that detached kinetochores compete with alternate binding sites in the nucleus to recruit Mad1 and Bub1 from available pools that are small enough to be fully depleted by just one pair of detached kinetochores and that lateral attachment licenses Mad1 removal from kinetochores after a kinetic delay.

| S-EPMC4501360 | biostudies-literature

A direct role of Mad1 in the spindle assembly checkpoint beyond Mad2 kinetochore recruitment.

Project description:The spindle assembly checkpoint (SAC) ensures accurate chromosome segregation by delaying entry into anaphase until all sister chromatids have become bi-oriented. A key component of the SAC is the Mad2 protein, which can adopt either an inactive open (O-Mad2) or active closed (C-Mad2) conformation. The conversion of O-Mad2 into C-Mad2 at unattached kinetochores is thought to be a key step in activating the SAC. The "template model" proposes that this is achieved by the recruitment of soluble O-Mad2 to C-Mad2 bound at kinetochores through its interaction with Mad1. Whether Mad1 has additional roles in the SAC beyond recruitment of C-Mad2 to kinetochores has not yet been addressed. Here, we show that Mad1 is required for mitotic arrest even when C-Mad2 is artificially recruited to kinetochores, indicating that it has indeed an additional function in promoting the checkpoint. The C-terminal globular domain of Mad1 and conserved residues in this region are required for this unexpected function of Mad1.

| S-EPMC3989694 | biostudies-literature

BubR1 is essential for kinetochore localization of other spindle checkpoint proteins and its phosphorylation requires Mad1.

Project description:The spindle checkpoint delays anaphase onset until all chromosomes have attached properly to the mitotic spindle. Checkpoint signal is generated at kinetochores that are not bound with spindle microtubules or not under tension. Unattached kinetochores associate with several checkpoint proteins, including BubR1, Bub1, Bub3, Mad1, Mad2, and CENP-E. I herein show that BubR1 is important for the spindle checkpoint in Xenopus egg extracts. The protein accumulates and becomes hyperphosphorylated at unattached kinetochores. Immunodepletion of BubR1 greatly reduces kinetochore binding of Bub1, Bub3, Mad1, Mad2, and CENP-E. Loss of BubR1 also impairs the interaction between Mad2, Bub3, and Cdc20, an anaphase activator. These defects are rescued by wild-type, kinase-dead, or a truncated BubR1 that lacks its kinase domain, indicating that the kinase activity of BubR1 is not essential for the spindle checkpoint in egg extracts. Furthermore, localization and hyperphosphorylation of BubR1 at kinetochores are dependent on Bub1 and Mad1, but not Mad2. This paper demonstrates that BubR1 plays an important role in kinetochore association of other spindle checkpoint proteins and that Mad1 facilitates BubR1 hyperphosphorylation at kinetochores.

| S-EPMC2173820 | biostudies-literature

Catalytic Receptors

Project description: Not available

| S-EPMC3315632 | biostudies-literature

The RZZ complex requires the N-terminus of KNL1 to mediate optimal Mad1 kinetochore localization in human cells.

Project description:The spindle assembly checkpoint is a surveillance mechanism that blocks anaphase onset until all chromosomes are properly attached to microtubules of the mitotic spindle. Checkpoint activity requires kinetochore localization of Mad1/Mad2 to inhibit activation of the anaphase promoting complex/cyclosome in the presence of unattached kinetochores. In budding yeast and Caenorhabditis elegans, Bub1, recruited to kinetochores through KNL1, recruits Mad1/Mad2 by direct linkage with Mad1. However, in human cells it is not yet established which kinetochore protein(s) function as the Mad1/Mad2 receptor. Both Bub1 and the RZZ complex have been implicated in Mad1/Mad2 kinetochore recruitment; however, their specific roles remain unclear. Here, we investigate the contributions of Bub1, RZZ and KNL1 to Mad1/Mad2 kinetochore recruitment. We find that the RZZ complex localizes to the N-terminus of KNL1, downstream of Bub1, to mediate robust Mad1/Mad2 kinetochore localization. Our data also point to the existence of a KNL1-, Bub1-independent mechanism for RZZ and Mad1/Mad2 kinetochore recruitment. Based on our results, we propose that in humans, the primary mediator for Mad1/Mad2 kinetochore localization is the RZZ complex.

| S-EPMC4680571 | biostudies-literature

CENP-I and Aurora B act as a molecular switch that ties RZZ/Mad1 recruitment to kinetochore attachment status.

Project description:The RZZ (Rod, ZW10, and Zwilch) complex and Mad1 proteins tightly associate with kinetochores to generate the spindle checkpoint signal, but they are released when a kinetochore forms mature microtubule attachments. Here we demonstrate that the centromere protein CENP-I is required to generate a stable association of RZZ and Mad1 with kinetochores. CENP-I also inhibits their removal by dynein stripping. This regulation of Mad1 and RZZ dissociation functions independently of Aurora B, which regulates their association. We show that the microtubule status of each kinetochore independently dictates the recruitment of Aurora B kinase, kinase activity on a kinetochore substrate, and loading of spindle checkpoint proteins. This dynamic regulation of Mad1 association by Aurora B is only uncovered when CENP-I is depleted, consistent with our finding that CENP-I inhibits the dissociation of Mad1. We conclude that the dual activities of Aurora B and CENP-I generate a molecular switch that maintains a robust spindle checkpoint signal at prometaphase kinetochores until they attain mature attachments to microtubules.

| S-EPMC4033774 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data