TRIP13 and APC15 drive mitotic exit by turnover of interphase- and unattached kinetochore-produced MCC

Abstract

The mitotic checkpoint ensures accurate chromosome segregation through assembly of the mitotic checkpoint complex (MCC), a soluble inhibitor of the anaphase-promoting complex/cyclosome (APC/C) produced by unattached kinetochores. MCC is also assembled during interphase by Mad1/Mad2 bound at nuclear pores, thereby preventing premature mitotic exit prior to kinetochore maturation and checkpoint activation. Using degron tagging to rapidly deplete the AAA+ ATPase TRIP13, we show that its catalytic activity is required to maintain a pool of open-state Mad2 for MCC assembly, thereby supporting mitotic checkpoint activation, but is also required for timely mitotic exit through catalytic disassembly of MCC. Strikingly, combining TRIP13 depletion with elimination of APC15-dependent Cdc20 ubiquitination/degradation results in a complete inability to exit mitosis, even when MCC assembly at unattached kinetochores is prevented. Thus, mitotic exit requires MCC produced either in interphase or mitosis to be disassembled by TRIP13-catalyzed removal of Mad2 or APC15-driven ubiquitination/degradation of its Cdc20 subunit.

Closure motif-mediated state changes of the HORMA protein ASY1

“…The findings here support a hypothesis that PCH2/TRIP13 proteins promote both the establishment and disassembly of the HORMAD signaling involved in different processes of both mitosis and meiosis in different organisms from yeast to animal and plant species. Our results support the finding that the defects in SAC activation in the absence of PCH2/TRIP13 are likely due to the deficiency of the conformational dynamics of the closed Mad2 (C-Mad2) to O-Mad2, thus abolishing MCC formation (19,40). Consistent with this assumption, the absence of PCH2/TRIP13 in C. elegans and human cells leads specifically Mad2 to an exclusively closed conformation and thus results in the failure of MCC assembly (33,39).…”

“…The necessity of PCH2 for both the chromosomal assembly and disassembly of ASY1 during meiosis largely resembles the roles of PCH2/TRIP13 orthologs in the spindle-assembly checkpoint (SAC), a mechanism ensuring that all chromosomes are attached to spindle fibers before anaphase and hence preventing aneuploidy (32)(33)(34)(35)(36). PCH2/TRIP13 proteins have been found to be required for not only the inactivation of SAC by disassembling the mitotic checkpoint complex (MCC) comprising BubR1, Bub3, CDC20 and the HORMA protein Mad2, but also for the establishment of the SAC by replenishing the opened Mad2 (O-Mad2) for MCC assembly (33,(37)(38)(39)(40). The findings here support a hypothesis that PCH2/TRIP13 proteins promote both the establishment and disassembly of the HORMAD signaling involved in different processes of both mitosis and meiosis in different organisms from yeast to animal and plant species.…”

HORMA domain proteins and a Pch2-like ATPase regulate bacterial cGAS-like enzymes to mediate bacteriophage immunity

“…Upon entrance into mitosis, large-scale assembly of Mad2 into a "mitotic checkpoint complex" with the closure motif-bearing protein Cdc20 overwhelms the disassembly capacity of Pch2/TRIP13, resulting in checkpoint activation. After successful kinetochore-microtubule attachment and cessation of mitotic checkpoint complex assembly, the checkpoint is inactivated as existing complexes are disassembled by Pch2/TRIP13 and an alternative pathway (Kim et al, 2018). In a similar manner, we propose that in the absence of a foreign threat, bacterial HORMA domain proteins are maintained in the inactive "open" state by continual activity of Pch2 (Fig.…”

“…Our data support a model for HORMA/Pch2 regulation of CD-NTase activity in bacteria that is remarkably reminiscent of the roles of Mad2 and Pch2/TRIP13 in the eukaryotic spindle assembly checkpoint. In this checkpoint pathway, the HORMA domain protein Mad2 is kept in its inactive open state through constant low-level conformational conversion by Pch2/TRIP13 (Kim et al, 2018;Poon, 2016, 2018). Upon entrance into mitosis, large-scale assembly of Mad2 into a "mitotic checkpoint complex" with the closure motif-bearing protein Cdc20 overwhelms the disassembly capacity of Pch2/TRIP13, resulting in checkpoint activation.…”

<p>Combinational phototherapy and hypoxia-activated chemotherapy favoring antitumor immune responses</p>

“…[9][10][11] In particular, checkpoint inhibitors and chimeric antigen receptor T-cell immunotherapy have been regarded as crucial tools for cancer treatment. [12][13][14][15][16][17][18][19][20] Nevertheless, the application of these two strategies is restricted due to serious side effects, high cost, and large individual variations. [21][22][23][24] More seriously, some tumor tissues, especially triple-negative breast cancer (TNBC), have relatively low immune response after treatment of checkpoint inhibitors, which is mainly attributed to "cold" immune microenvironment.…”