| Accurate chromosome segregation during mitosis is critical for maintaining genomic stability.The kinetochore,a large protein assembly on centromeric chromatin,functions as the docking site for spindle microtubules and a signaling hub for the spindle checkpoint.At metaphase,spindle microtubules from opposing spindle poles capture each pair of sister kinetochores,exert pulling forces,and create tension across sister kinetochores.The spindle checkpoint detects improper kinetochore-microtubule attachments and translates these defects into biochemical activities that inhibit the anaphase-promoting complex or cyclosome(APC/C)throughout the cell to delay anaphase onset.The APC/C is a large multisubunit ubiquitin ligase that triggers the metaphase to-anaphase transition in the cell cycle by targeting the substrates cyclin B and securin for destruction.APC/C activity toward these two key substrates requires the coactivator Cdc20.To ensure that cells enter mitosis and partition their duplicated genome with high accuracy,APC/CCcdc20 activity must be tightly controlled.Through genetic analyses,we found that deletion of dntl enhanced the temperature sensitivity of APC/C mutants.This genetic interaction was dependent on Mad2 and Mad3,and also partly on the E3 ubiquitin ligase Dmal.When Slpl was overexpressed twice of its endogenous level,the sensitivity of the dnt1 deletion strain to the microtubule depolymerising drug TBZ was slightly reversed.To search for potential functional homologous proteins,we tested mammalian proteins p31comet and CUEDC2.We found that overexpression of CUEDC2 slightly rescued the TBZ sensitivity of the dntl-deleted cells.Thus,fission yeast Dntl and mammalian CUEDC2 may have partially overlapping function.In summary,we discovered that Dntl is involved in regulating the activity of APC,and preliminary discussion of possible regulatory mechanisms. |
