Biology subjects

Marescal, O.

Publications and source records attributed to Marescal, O..

5 recordsLinked to original sources

bioRxiv2026

Functional genetics reveals a role for the proteasome in regulating centromere assembly

Centromeres link chromosomes to spindle microtubules to direct their segregation during mitosis. The vertebrate centromere is built on two critical DNA-binding proteins, the histone H3-variant CENP-A and histone fold protein CENP-T. CENP-T is a potent scaffold for kinetochore assembly, such that concentrating it at ectopic sites is sufficient to build kinetochore-like structures. How cells prevent excess CENP-T from acting at non-centromere sites remains unclear. Here, using optical pooled screening to systematically define the requirements for CENP-A and CENP-T localization, we recover the established CENP-A deposition machinery and reveal a specific role for the proteasome in controlling CENP-T levels. We find that non-centromere CENP-T is degraded in a ubiquitin- and proteasome-dependent manner. Whereas centromere-incorporated CENP-T is stable, CENP-T that is not bound to centromeres is rapidly turned over, with the CENP-T histone fold region sufficient to confer proteasome sensitivity. Quiescent cells, which disassemble their centromeres, continue to express CENP-T but eliminate it through continuous degradation. Thus, whereas CENP-A is controlled primarily through regulated deposition, cells additionally control CENP-T by selectively degrading the unincorporated protein.

cell biology↗

bioRxiv2026

A machine learning model predicts protein stability of annotated and alternate protein isoforms

The regulation of protein stability is essential for cellular homeostasis and is determined by a combination of intrinsic sequence motifs and extrinsic recognition enzymes. Despite growing knowledge of the protein degradation machinery, the ability to predict a proteins stability from its amino acid sequence remains challenging. Here we develop a machine learning model to predict protein stability from N-terminal amino acid sequences. Using our model and experimental validation, we identify known and novel sequence motifs governing protein stability. We additionally use this model to predict the stability of alternative translational isoforms with distinct N-termini produced from the same mRNA. Despite differing by a limited number of amino acids, we identify N-terminal isoforms with drastically different stabilities relative to their annotated counterparts, highlighting the potential of N-terminal extensions and truncations to regulate protein function. Together, this model provides a valuable tool for evaluating additional protein datasets and protein design strategies.

cell biology↗

bioRxiv2025

The dynamics of centromere assembly and disassembly during quiescence

Quiescence is a state in which cells undergo a prolonged proliferative arrest while maintaining their capacity to reenter the cell cycle. Here, we analyze entry and exit from quiescence, focusing on how cells regulate the centromere, a structure involved in chromosome segregation. Despite the constitutive localization of centromere proteins throughout the cell cycle, we find that cells rapidly disassemble most centromere proteins during quiescence entry, while preserving those required to maintain centromere identity. During quiescence exit, the centromere is reassembled and rapidly regains normal homeostatic levels of centromere proteins. Although the histone variant CENP-A is typically deposited during G1, we find that CENP-A deposition does not occur during the G1 immediately following quiescence exit, and instead occurs after cells complete their first mitosis. In contrast, other centromere proteins relocalize during the first S phase independent of DNA replication. These findings reveal centromere dynamics during quiescence entry and exit and highlight paradigms for the timing and control of centromere protein deposition.

cell biology↗

bioRxiv2025

19S proteasome loss causes monopolar spindles through ubiquitin-independent KIF11 degradation

To direct regulated protein degradation, the 26S proteasome recognizes ubiquitinated substrates through its 19S particle and then degrades them in the 20S enzymatic core. Despite this close interdependency between proteasome subunits, we demonstrate that knockouts from different proteasome subcomplexes result in distinct highly cellular phenotypes. In particular, depletion of 19S PSMD lid proteins, but not that of other proteasome subunits, prevents bipolar spindle assembly during mitosis, resulting in a mitotic arrest. We find that the monopolar spindle phenotype is caused by ubiquitin- independent proteasomal degradation of the motor protein KIF11 upon loss of 19S proteins. Thus, negative regulation of 20S-mediated proteasome degradation is essential for mitotic progression and 19S and 20S proteasome components can function independently outside of the canonical 26S structure. This work reveals a role for the proteasome in spindle formation and identifies the effects of ubiquitin- independent degradation on cell cycle control.

cell biology↗

bioRxiv2021

Oxoglutarate dehydrogenase coordinates myofibril growth by maintaining amino acid homeostasis

Myofibrils are long intracellular cables specific to muscles, composed mainly of actin and myosin filaments. The actin and myosin filaments are organized into repeated units called sarcomeres, which form the myofibril cables. Muscle contraction is achieved by the simultaneous shortening of sarcomeres and for a highly coordinated contraction to occur all sarcomeres should have the same size. Muscles have evolved a variety of ways to ensure sarcomere homogeneity, one example being the controlled oligomerization of Zasp proteins that sets the diameter of the myofibril. To understand how Zasp proteins effect myofibril growth, we looked for Zasp-binding proteins at the Z-disc. We found that the E1 subunit of the oxoglutarate dehydrogenase complex is recruited to the Z-disc by Zasp52 and is required to sustain myofibril growth. By making specific mutants, we show that its enzymatic activity is important for myofibril growth, and that the other two subunits of the complex are also required for myofibril formation. Using super resolution microscopy, we revealed the overall organization of the complex at the Z-disc. Then, using metabolomic analysis, we uncovered an amino acid balance defect affecting protein synthesis, that we also confirmed by genetic tools. In summary, we show that Zasp controls the local amino acid pool responsible for myofibril growth by recruiting the OGDH complex to the Z-disc.

cell biology↗