Speriolin is a sperm centrosome protein []that form a complex with CDC20, CDC27 and TUBG1. It interacts with Cdc20 and is only detected in testis in humans [, ]. The function of speriolin and speriolin-like proteins is unknown.
Proteins containing this domain are checkpoint proteins involved in cell division. This region has been shown to be essential for the binding of Bub1 and Mad3 to Cdc20 [].
Human ANAPC15 is a component of the anaphase promoting complex/cyclosome (APC/C), a cell cycle-regulated E3 ubiquitin ligase that controls progression through mitosis and the G1 phase of the cell cycle. In the complex, it plays a role in the release of the mitotic checkpoint complex (MCC) from the APC/C; it is not required for APC/C activity itself, but promotes the turnover of CDC20 and MCC on the APC/C, thereby participating to the responsiveness of the spindle assembly checkpoint. It also required for degradation of CDC20 [].
This entry represents the C terminus of the sperm centrosome protein speriolin [, ].Speriolin is a sperm centrosome protein []that form a complex with CDC20, CDC27 and TUBG1. It interacts with Cdc20 and is only detected in testis in humans [, ]. The function of speriolin and speriolin-like proteins is unknown.
This represents the mitotic checkpoint serine/threonine-protein kinase Bub1. Saccharomyces cerevisiae Bub1 has a paralogue, Mad3, which is also included in this entry. Bub1 forms a complex with Mad1 and Bub3 that is crucial for preventing cell cycle progression into anaphase in the presence of spindle damage [], while Mad3 is a component of the spindle-assembly complex consisting of Mad2, Mad3, Bub3 and Cdc20 []. Mad3 contains a D-box and two KEN- boxes, which function together to mediate Cdc20-Mad3 interaction. Mad3 and an anaphase-promoting complex (APC) substrate, Hsl1, compete for Cdc20 binding in a D-box- and KEN-box-dependent manner [].Similar to its yeast homologues, human Bub1 is a critical component of the mitotic checkpoint that delays the onset of anaphase until all chromosomes have established bipolar attachment to the microtubules. In interphase cells it localises to centrosomes and suppresses centrosome amplification via regulating Plk1 activity []. Mutations in the human Bub1 gene have been linked to cancers [, ].
This family consists of pindle assembly checkpoint protein Mad1. The mitotic spindle checkpoint monitors proper attachment of the bipolar spindle to the kinetochores of aligned sister chromatids and causes a cell cycle arrest in prometaphase when failures occur. Multiple components of the mitotic spindle checkpoint have been identified in Saccharomyces cerevisiae and higher eukaryotes. In Saccharomyces cerevisiae, the existence of a Mad1-dependent complex containing Mad2, Mad3, Bub3 and Cdc20 has been demonstrated [].
This entry represents Mad1 and Cdc20-bound-Mad2 binding proteins that are involved in the cell-cycle surveillance mechanism called the spindle checkpoint []. This mechanism monitors the proper bipolar attachment of sister chromatids to spindle microtubules and ensures the fidelity of chromosome segregation during mitosis. A key player in mitosis is Mad2, which exhibits an unusual two-state behaviour. A Mad1-Mad2 core complex recruits cytosolic Mad2 to kinetochores through Mad2 dimerisation and converts Mad2 to a conformer amenable to Cdc20 binding. p31comet inactivates the checkpoint by binding to Mad1- or Cdc20-bound Mad2 in such a way as to stop Mad2 activation and to promote the dissociation of the Mad2-Cdc20 complex [].
The anaphase promoting complex/cyclosome (APC/C) is a cell cycle-regulated E3 ubiquitin ligase that controls progression through mitosis and the G1 phase of the cell cycle. The APC/C consists of thirteen different subunits and, in somatic cells, has two co-activators: Cdc20 and Cdh1 (also known as Fzr1), which associate with the APC/C core at defined stages of the cell cycle. APC/C is only active between metaphase and the end of the next G1 phase. During this time, APC/CCdc20 initiates anaphase and mitotic exit,while APC/CCdh1 contributes to mitotic exit and establishment of a stable G1 state []. This entry represents the APC/C subunit 16 [].
Mad2 is a central component of the spindle assembly checkpoint, which is a feedback control that prevents cells with incompletely assembled spindles from leaving mitosis [, ]. In Saccharomyces cerevisiae, it is a component of the mitotic checkpoint complex (MCC) which consists of MAD2, MAD3, BUB3 and CDC20, and of the MAD2-CDC20 subcomplex, both of which appear to be assembled during mitoisis independently of the kinetochore. MCC and presumably the MAD2-CDC20 subcomplex inhibit the ubiquitin ligase activity of the anaphase promoting complex/cyclosome (APC/C) by preventing its activation by CDC20 [, , ].
The anaphase promoting complex/cyclosome (APC/C) is a multisubunit ubiquitin ligase that targets mitotic regulators for degradation in exit from mitosis. At the end of mitosis, APC/C is activated by phosphorylation and association with the WD-40 protein Cdc20/Fizzy []. The inhibitory phosphorylation of Cdc20/Fizzy may have a role as a safeguard to keep the cyclosome inactive in early mitosis and under conditions of mitotic checkpoint arrest []. This entry includes Cdc20/Fizzy homologues from fungi, plants and animals.Three characterised budding yeasts homologues are included in this entry: Cdc20, Cdh1 and Ama1. Cdc20 and Cdh1 have been shown to activate APC/C during mitosis, while Ama1 is a meiosis-specific activator of the APC/C []. The APC/C-Cdh1 is also found involved in the cellular response to DNA damage []. Protein cortex from Drosophila melanogasterwhich is a female meiosis-specific activator of the anaphase promoting complex/cyclosome (APC/C) required for the completion of meiosis in oocytes, is also included in this entry. Cortex activates the ubiquitin ligase activity and substrate specificity of APC/C and triggers the sequential degradation of mitotic cyclins in meiosis [, ].
