Nuclear-cytoplasmic compartmentalization of cyclin B1-Cdk1 promotes robust timing of mitotic events

• Published in: Cell reports (Cambridge) 2022-12, Vol.41 (13), p.111870-111870, Article 111870
• Main Authors: Maryu, Gembu, Yang, Qiong
• Format: Article
• Language: English
• Subjects: CDC2 Protein Kinase - metabolism; cell cycle robustness; Cell Nucleus - metabolism; cell-free extracts; Cyclin B1 - metabolism; cyclin-dependent kinase (Cdk); Cyclin-Dependent Kinases - metabolism; droplet microfluidics; frequency tunability; FRET imaging; limit-cycle oscillations; Mitosis; nuclear-cytoplasmic compartmentalization; phase-plane trajectory; Phosphorylation; synthetic cells
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2022.111870

The cyclin-dependent kinase (Cdk1) oscillator is widely characterized in homogenized cytosolic extracts, leaving unclear the impact of nucleocytoplasmic compartmentalization. Here, by developing a Förster resonance energy transfer (FRET) biosensor, we track Cdk1 spatiotemporal dynamics in reconstituted cells with or without side by side and find compartmentalization significantly modulates clock properties previously found in bulk studies. Although nucleus-absent cells display highly tunable frequency, the nucleus-present cells maintain constant frequency against cyclin B1 variations. Despite high expression variability, cyclin degraded within the same duration, enabling a robust mitotic phase. Moreover, Cdk1 and cyclin B1 cycle rigorously out-of-phase, ensuring wide phase-plane orbits, essential for oscillation robustness. Although Cdk1 in homogeneous extracts is well known for delayed switch-like activation, we find active cyclin B1-Cdk1 accumulates in nuclei, without delay, until the nuclear envelope breakdown (NEB) when another abrupt activation triggers anaphase. Cdk1 biphasic activation and spatial compartmentalization may together coordinate the accurate ordering of different downstream events. [Display omitted] •Cdk1-EV tracks single-cell Cdk1 spatiotemporal dynamics for phase-plane orbit•Compartmentalized Cdk1 turns a delayed bistable switch into biphasic activation•Tunable Cdk1 clock in homogeneous cytosol becomes robust when nuclei are present•Scalable degradation allows robust mitosis despite noisy cyclin B1 levels Compartmentalization, a ubiquitous feature of eukaryotic cells, provides spatiotemporal segregation to ensure faithful cellular processes. Maryu and Yang show that compared with a homogeneous microenvironment, nucleocytoplasmic compartmentalization of a mitotic master regulator Cdk1 significantly changes its activation profile, enhances clock robustness, and ensures correct order of downstream mitotic events.