Biology subjects

Royou, A.

Publications and source records attributed to Royou, A..

3 recordsLinked to original sources

bioRxiv2025

A cyclin-polarity feedback network ensures healthy cell proliferation

Healthy proliferation requires the coordination of cell cycle progression with cell polarity. In budding yeast, polarity is established when G1-cyclin-Cdc28Cdk1 triggers Cdc42 activation to generate a cell pole that is used as an axis for growth and division. While polarity defects delay the cell cycle temporally, permitting error correction, it is unknown if Cdc28Cdk1 directly rectifies errant polarity. Here, we identify an adaptive response where G1-cyclin-Cdc28Cdk1 participates in error correction via the augmentation of its kinase activity towards substrates that activate Cdc42. The response involves temporal and spatial cell cycle reconfiguration via extended G1 cyclin expression, nucleocytoplasmic rerouting and signaling. However, this strategy has a cost: if the defect is irreparable, high G1-cyclin levels enforce inexorable cell cycle commitment in the absence of a daughter cell, generating multinucleate cells. G1-cyclins therefore not only trigger G1 events, but also monitor their execution, employing feedback to coordinate polarity with cell cycle progression.

cell biology↗

bioRxiv2023

Uncovering the multi-step process of stable microtubule bundle formation upon entry into quiescence

Cells fine-tune microtubule assembly in both space and time, to give rise to distinct edifices with specific cellular functions. In proliferating cells, microtubules are highly dynamics, and proliferation cessation often leads to their stabilization. One of the most stable microtubule structures identified to date is the nuclear bundle assembled in quiescent yeast. In this report, we characterize the original multistep process driving the assembly of this structure. This Aurora B-dependent mechanism follows a precise temporality that relies on the sequential actions of kinesin-14, kinesins-5 and involves both microtubule-kinetochore and kinetochore-kinetochore interactions. Upon quiescence exit, the microtubule bundle is disassembled via a cooperative process involving kinesin-8 and its full disassembly is required prior to cells re-entry into proliferation. Overall, our study provides the first description, at the molecular scale, of the entire life cycle of a stable microtubule structure in vivo, and sheds light on its physiological function.

cell biology↗

bioRxiv2022

Two RhoGEF isoforms with distinct localisation act in concert to control asymmetric cell division

Cytokinesis is essential for the partitioning of cellular contents into daughter cells. It relies on the formation of an acto-myosin contractile ring, whose constriction induces the ingression of the cleavage furrow between the segregated chromatids. Rho1 GTPase and its RhoGEF (Pbl) are essential for this process as they drive the assembly and constriction of the contractile ring. However, how Rho1 is regulated to sustain efficient furrow ingression while maintaining correct furrow position remains poorly defined. Here, we show that during asymmetric division of Drosophila neuroblasts, Rho1 is controlled by two Pbl isoforms with distinct localisation. Spindle midzone- and furrow-enriched Pbl-A focuses Rho1 at the furrow to sustain efficient ingression, while Pbl-B pan-plasma membrane localization promotes the broadening of Rho1 activity and the subsequent enrichment of cortical myosin. This enlarged zone of Rho1 activity becomes essential to adjust furrow position during ingression, thereby preserving correct daughter cell size asymmetry. Our work highlights how the use of isoforms with distinct localisation patterns provides robustness to an essential process.

cell biology↗