biostudies-literatureLara-Gonzalez PODCDC CDC HHSNational Institutes of HealthNIH Office of Research Infrastructure ProgramsLudwig Institute for Cancer ResearchNIH HHSNIGMS NIH HHSe202308034https://www.ebi.ac.uk/biostudies/studies/S-EPMC11303871biostudies-literatureUnknown223(11)Mitosis in early embryos often proceeds at a rapid pace, but how this pace is achieved is not understood. Here, we show that cyclin B3 is the dominant driver of rapid embryonic mitoses in the C. elegans embryo. Cyclins B1 and B2 support slow mitosis (NEBD to anaphase ∼600 s), but the presence of cyclin B3 dominantly drives the approximately threefold faster mitosis observed in wildtype. Multiple mitotic events are slowed down in cyclin B1 and B2-driven mitosis, and cyclin B3-associated Cdk1 H1 kinase activity is ∼25-fold more active than cyclin B1-associated Cdk1. Addition of cyclin B1 to fast cyclin B3-only mitosis introduces an ∼60-s delay between completion of chromosome alignment and anaphase onset; this delay, which is important for segregation fidelity, is dependent on inhibitory phoThe Journal of cell biologyCyclin B3 is a dominant fast-acting cyclin that drives rapid early embryonic mitoses.PMC11303871R35 GM150786GM147265GM074215F32GM145068P40 OD010440S10 OD021724R01 GM074215R01 GM147265GM150786F32 GM145068Schlientz AVariyar SBudrewicz JOegema KVarshney NBellaart ADesai ALara-Gonzalez PNguyen ACNKizhedathu AMoghareh SBardwell LfalseCyclin B3 is a dominant fast-acting cyclin that drives rapid early embryonic mitoses.Mitosis in early embryos often proceeds at a rapid pace, but how this pace is achieved is not understood. Here, we show that cyclin B3 is the dominant driver of rapid embryonic mitoses in the C. elegans embryo. Cyclins B1 and B2 support slow mitosis (NEBD to anaphase ∼600 s), but the presence of cyclin B3 dominantly drives the approximately threefold faster mitosis observed in wildtype. Multiple mitotic events are slowed down in cyclin B1 and B2-driven mitosis, and cyclin B3-associated Cdk1 H1 kinase activity is ∼25-fold more active than cyclin B1-associated Cdk1. Addition of cyclin B1 to fast cyclin B3-only mitosis introduces an ∼60-s delay between completion of chromosome alignment and anaphase onset; this delay, which is important for segregation fidelity, is dependent on inhibitory pho2024-01-01T00:00:00Z2024 Nov2026-06-02T10:17:18.899Z2025-04-19T06:00:24.698ZS-EPMC113038713910575610.1083/jcb.202308034