Biology subjects

Metson, J.

Publications and source records attributed to Metson, J..

3 recordsLinked to original sources

bioRxiv2025

Enzymes can activate and mobilize the cytoplasmic environment across scales

Biomolecular condensates have so far been studied in terms of their structural, compositional, and functional properties. However, condensate enzymatic activity --a key aspect of cellular metabolism-- remains unexplored due to the complexity of the system. In this study, using a combination of experimental, computational and theoretical techniques, we have discovered that the non-equilibrium activity which originates from catalytic reactions couples with the environment through various feedback mechanisms across five orders of magnitude of length scales. We observe that condensed enzymes catalyse more rapidly in the presence of crowding proteins and show that the increased enzymatic activity within these droplets stems from the emergence of lower-energy protein conformations induced by the highly crowded environment. Despite the crowding in the environment of the droplet, which might suggest an effective increase in its overall viscosity, we find that it becomes more agile, as evidenced by the observation of enhanced diffusion and macroscopic flow, due to the enzymatic activity. These findings shed new light on the dynamic interplay between enzymatic activity, composition and crowding in condensates, and their roles on the mobility and accessibility of various functional units in these environments, offering a novel perspective on liquidliquid phase separation in metabolically active conditions.

biochemistry↗

bioRxiv2020

Scc2 and Scc3 promote distinct modes of topological association between cohesin and DNA

In addition to extruding DNA loops, cohesin entraps within its SMC-kleisin ring (S-K) individual DNAs during G1 and sister DNAs during S-phase. All three activities require related hook-shaped proteins called Scc2 and Scc3. Using thiol-specific crosslinking we provide rigorous proof of entrapment activity in vitro. Scc2 alone promotes entrapment of DNAs in the E-S and E-K compartments, between ATP-bound engaged heads and the SMC hinge and associated kleisin, respectively. This does not require ATP hydrolysis nor is it accompanied by entrapment within S-K rings, which is a slower process requiring Scc3. Cryo-EM reveals that DNAs transported into E-S/E-K compartments are "clamped" in a sub-compartment created by Scc2s association with engaged heads whose coiled coils are folded around their elbow. We suggest that clamping may be a recurrent feature of cohesin complexes active in loop extrusion and that this conformation precedes the S-K entrapment required for sister chromatid cohesion.

biochemistry↗

bioRxiv2020

Loss of Sister Kinetochore Co-orientation and Peri-centromeric Cohesin Protection after Meiosis I Depends on Cleavage of Centromeric REC8

Protection of peri-centromeric REC8 cohesin from separase and sister kinetochore attachment to microtubules emanating from the same spindle pole (co-orientation) ensure that sister chromatids remain associated after meiosis I. Both features are lost during meiosis II, when sister kinetochores bi-orient and lose peri-centromeric REC8 protection, resulting in sister chromatid disjunction and the production of haploid gametes. By transferring spindle-chromosome complexes (SCCs) between meiosis I and II cells, we have discovered that both sister kinetochore co-orientation and peri-centromeric cohesin protection depend on the SCC and not the cytoplasm. Moreover, the catalytic activity of separase at meiosis I is necessary not only for converting kinetochores from a co-to a bi-oriented state but also for deprotection of peri-centromeric cohesin and that cleavage of REC8 may be the key event. Crucially, we show that selective cleavage of REC8 in the vicinity of kinetochores is sufficient to destroy co-orientation in univalent chromosomes, albeit not in bivalents where resolution of chiasmata through cleavage of Rec8 along chromosome arms may also be required.

cell biology↗