The conserved AAA-ATPase PCH-2^TRIP13regulates spindle checkpoint strength

Abstract

Spindle checkpoint strength is dictated by the number of unattached kinetochores, cell volume and cell fate. We show that the conserved AAA-ATPase, PCH-2/TRIP13, which remodels the checkpoint effector Mad2 from an active conformation to an inactive one, controls checkpoint strength in C. elegans. Having previously established that this function is required for spindle checkpoint activation, we demonstrate that in cells genetically manipulated to decrease in cell volume, PCH-2 is no longer required for the spindle checkpoint or recruitment of Mad2 at unattached kinetochores. This role is not limited to large cells: the stronger checkpoint in germline precursor cells also depends on PCH-2. PCH-2 is enriched in germline precursor cells and this enrichment relies on conserved factors that induce asymmetry in the early embryo. Finally, the stronger checkpoint in germline precursor cells is regulated by CMT-1, the ortholog of p31comet, which is required for both PCH-2’s localization to unattached kinetochores and its enrichment in germline precursor cells. Thus, PCH-2, likely by regulating the availability of inactive Mad2 at and near unattached kinetochores, governs checkpoint strength. This requirement may be particularly relevant in oocytes and early embryos enlarged for developmental competence, cells that divide in syncytial tissues and immortal germline cells. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text]

Meiotic cells escape prolonged spindle checkpoint activity through kinetochore silencing and slippage

“…Similarly, checkpoint strength is thought to be at least partially dependent on cell size in the oocyte and developing C . elegans embryo [ 70 – 72 ]. To determine if a size difference could be causing a weaker spindle checkpoint in meiotic budding yeast cells, we measured the volume of budding yeast cells at the time point just before anaphase onset and found that mek1Δ cells in meiosis had a volume of 254 ± 46 fL, while Cdc6-dp cells had an average volume of 343 ± 89 fL ( S1B Fig ).…”

“…Mouse oocytes have a weaker spindle checkpoint than mitotic cells, which is thought to be due to their larger size [62][63][64][65][66][67][68][69]. Similarly, checkpoint strength is thought to be at least partially dependent on cell size in the oocyte and developing C. elegans embryo [70][71][72]. To determine if a size difference could be causing a weaker spindle checkpoint in meiotic budding yeast cells, we measured the volume of budding yeast cells at the time point just before anaphase onset and found that mek1Δ cells in meiosis had a volume of 254 ± 46 fL, while Cdc6-dp cells had an average volume of 343 ± 89 fL (S1B Fig) . From this we conclude that cells arrested in mitosis have a larger average volume compared to cells arrested in meiosis, so it is not likely that the inherent weakness of the meiotic checkpoint is due to a larger cell volume.…”

The conserved AAA ATPase PCH-2 distributes its regulation of meiotic prophase events through multiple meiotic HORMADs in C. elegans

“…This activity may not necessarily be conserved, given that a similar role in silencing the checkpoint is not observed in C . elegans [ 59 , 62 ], and Pch2 is not expressed outside meiosis in S . cerevisiae [ 38 ].…”

The conserved AAA-ATPase PCH-2 distributes its regulation of meiotic prophase events by remodeling multiple meiotic HORMADs inC. elegans

“…After kinetochore attachment, TRIP13 plays an additional role in human cells, disassembling the mitotic checkpoint complex by remodeling MAD2, promoting checkpoint inactivation and anaphase progression [60, 61]. This activity may not necessarily be conserved, given that a similar role in silencing the checkpoint is not observed in C. elegans [59, 62], and Pch2 is not expressed outside meiosis in S. cerevisiae [38]. Nonetheless, in some systems, TRIP13 appears to play dual roles in spindle checkpoint activation and inactivation, through a single biochemical activity of converting “closed” MAD2 to the “open” conformer.…”