Biology subjects

Balestra, F. R.

Publications and source records attributed to Balestra, F. R..

3 recordsLinked to original sources

bioRxiv2022

Centriolar subdistal appendages promote double strand break repair through homologous recombination

The centrosome is a cytoplasmic organelle with roles in microtubule organization which has also been proposed to act as a hub for cellular signaling. Some centrosomal components are required for full activation of the DNA Damage Response. However, if the centrosome regulates specific DNA repair pathways is not known. Here, we show that centrosomes presence is required to fully activate recombination, specifically to completely license its initial step, the so-called DNA end resection. Furthermore, we identify a centriolar structure, the subdistal appendages, and a specific factor, CEP170, as the critical centrosomal component involved in the regulation of recombination and resection, albeit it does not control end-joining repair. Cells lacking centrosomes or depleted for CEP170 are, consequently, hyper-sensitive to DNA damaging agents. Moreover, low levels of CEP170 in multiple cancer types correlate with an increase of the mutation burden associated with specific mutational signatures and a better prognosis, suggesting that changes in CEP170 can act as a mutation driver but also could be targeted to improve current oncological treatments.

cell biology↗

bioRxiv2020

TRIM37 prevents formation of centriolar protein assemblies by regulating Centrobin stability

TRIM37 is an E3 ubiquitin ligase mutated in Mulibrey nanism, a disease characterized by impaired growth and increased tumorigenesis, whose cellular etiology is poorly understood. TRIM37 depletion from tissue culture cells results in supernumerary foci bearing the centriolar protein Centrin. Here, we characterized these centriolar protein assemblies (Cenpas) to uncover the mechanism of action of TRIM37. We established that an atypical de novo assembly pathway is notably involved in forming Cenpas, which can nevertheless trigger further centriole assembly and act as MTOCs. We found also that Cenpas are present and act similarly in Mulibrey patient cells. Through correlative light electron microscopy, we uncovered that Cenpas correspond to centriole related structures and elongated electron-dense structures with stripes. Importantly, we established that TRIM37 regulates the stability and solubility of the centriolar protein Centrobin. Our findings suggest that elongated Centrobin assemblies are a major constituent of the striped electron dense structures. Furthermore, we established that Cenpas formation upon TRIM37 depletion requires PLK4 activity, as well as two parallel pathways relying respectively on Centrobin and PLK1. Overall, our work uncovers how TRIM37 prevents the formation of Cenpas that would otherwise threaten genome integrity, including possibly in Mulibrey patients.

cell biology↗

bioRxiv2017

The Centrosome Controls the Number and Spatial Distribution of Microtubules by Negatively Regulating Alternative MTOCs

In this work, we have investigated in mammalian cells how microtubule nucleation at centrosome and Golgi apparatus are coordinated, using genetic ablation of three {gamma}-TuRC binding proteins -AKAP450, Pericentrin and CDK5Rap2- and the PLK4 inhibitor centrinone. We show that centrosomal microtubule nucleation is independent of Golgi activity whereas the converse is not true: nucleation on the Golgi negatively correlates with the number of centrosomes. In addition, depleting AKAP450 in cells lacking centrioles, that abolishes Golgi nucleation activity, leads to microtubule nucleation from numerous cytoplasmic Golgi-unbound acentriolar structures containing Pericentrin, CDK5Rap2 and y-tubulin. Strikingly, centrosome-less cells display twice higher microtubule density than normal cells, suggesting that the centrosome controls the spatial distribution of microtubules, not only by nucleating them, but also by acting as a negative regulator of alternative MTOCs. Collectively, the data reveals a hierarchical control of microtubule nucleation, with the centrosome regulating this process in a more complex manner than usually thought. It also unveils mechanisms that could help understanding MT network reorganization during cell differentiation.

cell biology↗