Figure 4.

Kinetochore-localized PP1c is the likely enzyme dephosphorylating CDC-20 fluxing through the kinetochore. (A, top) Schematic of KNL-1 primary structure; the PP1-binding site (SILK–RRVSF), the “MELT” repeats that recruit the BUB-1/BUB-3 complex when phosphorylated, and the mutations engineered in KNL-1 to disrupt PP1c binding (PP1c Mut) are depicted. (Bottom) Images (left) and quantification (right) of chromosomal fluorescence for BUB-1::GFP and GFP::CDC-20 in the indicated conditions. (****) P < 0.0001 (Mann-Whitney test). Bar, 2 µm. (B–D) Quantification of the NEBD–anaphase onset interval of embryos expressing GFP::H2b for the indicated conditions. (****) P < 0.0001 (Mann-Whitney test). (E) Model summarizing the two opposing fates of CDC-20 fluxing through the kinetochore. Microtubule attachment shifts the balance by removing the MAD-1/MAD-2 checkpoint complex and potentially also by promoting PP1c kinetochore recruitment. See also Supplemental Figure S5.