Spindle Checkpoint Silencing Requires Association of PP1 to Both Spc7 and Kinesin-8 Motors

Abstract

The spindle checkpoint is the prime cell-cycle control mechanism that ensures sister chromatids are bioriented before anaphase takes place. Aurora B kinase, the catalytic subunit of the chromosome passenger complex, both destabilizes kinetochore attachments that do not generate tension and simultaneously maintains the spindle checkpoint signal. However, it is unclear how the checkpoint is silenced following chromosome biorientation. We demonstrate that association of type 1 phosphatase (PP1(Dis2)) with both the N terminus of Spc7 and the nonmotor domains of the Klp5-Klp6 (kinesin-8) complex is necessary to counteract Aurora B kinase to efficiently silence the spindle checkpoint. The role of Klp5 and Klp6 in checkpoint silencing is specific to this class of kinesin and independent of their motor activities. These data demonstrate that at least two distinct pools of PP1, one kinetochore associated and the other motor associated, are needed to silence the spindle checkpoint.

Pre-anaphase chromosome oscillations are regulated by the antagonistic activities of Cdk1 and PP1 on Kif18A

“…Metaphase plate thinning occurs as cells progress towards anaphase implicating the existence of a phosphatase that counteracts Cdk1 phosphorylation of Kif18A. Previous studies revealed that Klp5/Klp6, the fission yeast Kinesin-8, contain a conserved motif (R/KxVxF/W; x denoting any aa) that mediates binding to protein phosphatase-1 (PP1) 25 . To test the idea that PP1 is the phosphatase that antagonizes Cdk1, we first analysed if Kif18A interacts with PP1.…”

“…Notably, an interaction between Kinesin-8 and PP1 has been recently reported for fission yeast Klp5/Klp6 and this interaction has been shown to be essential for timely SAC silencing 25 . Our data revealed that the expression of Kif18A deficient in PP1 binding (GFP-Kif18A PP1D ) as well causes a delay in anaphase onset (Fig.…”

Collaborative Control of Cell Cycle Progression by the RNA Exonuclease Dis3 and Ras Is Conserved Across Species

“…Here, we draw a parallel to dis2/PP1, a gene that displays similar cell cycle phenotypes to dis3 in S. pombe and flies (Ohkura et al 1988;Axton et al 1990). During mitosis, Dis2/PP1 activity is thought to prevent chromosome separation until all chromosome pairs are bioriented on the mitotic spindle (Vanoosthuyse and Hardwick 2009;Meadows et al, 2011); once this criterion is met, its activity is thought to be directly Figure 7 dis3 and ras cooperate to accelerate cells through the G2/M phase. Graph shows the relative percentage of cells of the indicated genotype in the G1, S, and G2/M phases of the cell cycle.…”

Role and regulation of kinesin-8 motors through the cell cycle

“…Importantly, cells expressing a motor defective Klp5-Klp6 complex display all of these phenotypes, indicating that motor activity is important for kinesin-8 function. However it has been shown recently that the non-motor tail domains of Klp5 and Klp6 bind to type 1 phosphatase (PP1) and that this pool of PP1 helps to regulate both mitotic microtubule mechanics and efficiently silence the spindle checkpoint (Meadows et al 2011 …”