A landmark event in the transition from interphase to mitosis in metazoans is nuclear envelope breakdown (NEBD). Important mitotic events occur prior to NEBD, including condensation of replicated chromosomes and assembly of kinetochores to rapidly engage spindle microtubules. Here, we show that nuclear-enriched protein phosphatase 4 (PP4) ensures robust assembly of the microtubule-coupling outer kinetochore prior to NEBD. In the absence of PP4, chromosomes exhibit extended monopolar orientation after NEBD and subsequently mis-segregate. A secondary consequence of diminished outer kinetochore assembly is defective sister chromatid resolution. After NEBD, a cytoplasmic activity compensates for PP4 loss, leading to outer kinetochore assembly and recovery of chromosomes from monopolar orientation to significant bi-orientation. The Ndc80-Ska microtubule-binding module of the outer kinetochore is required for this recovery. PP4 associates with the inner kinetochore protein CENP-C; however, disrupting the PP4–CENP-C interaction does not perturb chromosome segregation. These results establish that PP4-dependent outer kinetochore assembly prior to NEBD is critical for timely and proper engagement of chromosomes with spindle microtubules.
Nuclear-enriched protein phosphatase 4 ensures outer kinetochore assembly prior to nuclear dissolution
Disclosures: The authors declare no competing interests exist.
J. Budrewicz's current affiliation is Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR, USA and Division of Reproductive & Developmental Sciences, Oregon National Primate Research Center, Beaverton, OR, USA.
P. Lara-Gonzalez's current affiliation is Department of Developmental and Cell Biology, School of Biological Sciences, University of California Irvine, Irvine, CA, USA.
- Award Id(s): P40 OD010440
- Award Id(s): ERC-2013-StG-338410-DYNEINOME
- Award Id(s): CEECIND/00333/2017,SFRH/BD/103495/2014,UIDB/04293/2020
- Award Id(s): PTDC/BIA-CEL/30507/2017
Helder Rocha, Patrícia A. Simões, Jacqueline Budrewicz, Pablo Lara-Gonzalez, Ana Xavier Carvalho, Julien Dumont, Arshad Desai, Reto Gassmann; Nuclear-enriched protein phosphatase 4 ensures outer kinetochore assembly prior to nuclear dissolution. J Cell Biol 6 March 2023; 222 (3): e202208154. doi: https://doi.org/10.1083/jcb.202208154
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