bims-micesi 2025-07-20 papers

Issue of 2025–07–20
three papers selected by
Valentina Piano, Uniklinik Köln

Eur J Cell Biol. 2025 Jul 09. pii: S0171-9335(25)00031-7. [Epub ahead of print]104(3): 151506

A diverse interactome of the molecular chaperone CCT/TRiC monomers.

Carmen M Córdoba-Beldad, Julie Grantham.

The molecular chaperone CCT is essential in eukaryotes where it is required for the folding of actin and tubulin. Extensive studies have defined interactomes of the assembled CCT oligomer where binding partners include obligate folding substrates, opportunistic substrates and regulatory proteins. In addition to folding, the CCT oligomer acts as a sequestering complex and several of the individual CCT subunits, when monomeric, are known to possess functions distinct from folding. Here the first interactome of the individual subunits as monomers is defined by yeast 2-hybrid screening, revealing an array of subunit-specific interaction partners linked to diverse cellular functions. We identify, by live cell imaging/ fluorescence microscopy following siRNA depletions, CCT subunit-specific effects on cell cycle progression and show that CCT5 influences localisation of KNL1 to the kinetochore. Our results reveal the extent of CCT monomer interactions, which are essential for a complete understanding of the cellular functions of CCT.

Keywords: Cell cycle; Chaperonin; Cytoskeleton; Kinetochore; Microtubule

DOI: https://doi.org/10.1016/j.ejcb.2025.151506

EMBO Rep. 2025 Jul 15.

A pivot-tether model for nucleosome recognition by the chromosomal passenger complex.

Reinis R Ruza, Chyi Wei Chung, Danny B H Gold, Michela Serena, Emile Roberts, Ulrike Gruneberg, Francis A Barr.

Spatial restriction of Aurora B to T3-phosphorylated histone H3 (H3pT3) nucleosomes adjacent to centromeres during prometaphase and metaphase enables it to phosphorylate proteins necessary for spindle assembly checkpoint signalling and biorientation of chromosomes on the mitotic spindle. Aurora B binding to H3pT3-nucleosomes requires a multivalent targeting module, the chromosomal passenger complex (CPC), consisting of survivin, borealin, and INCENP. To shed light on how these components mediate CPC localisation during prometaphase and metaphase, we determined the structure of the CPC targeting module in complex with haspin-phosphorylated H3pT3-nucleosomes by cryo-electron microscopy. This structure shows how the N-terminus of borealin and the survivin BIR domain act as pivot and flexible tethering points, respectively, to increase CPC affinity for H3pT3 nucleosomes without limiting it to a specific orientation. We demonstrate that this flexible, yet constrained pivot-tether arrangement is important for the control of spindle assembly checkpoint signalling by Aurora B.

Keywords: Aurora Kinase B; Centromeres; Mitosis; Nucleosomes; Spindle Assembly Checkpoint

DOI: https://doi.org/10.1038/s44319-025-00523-4

Curr Opin Plant Biol. 2025 Jul 15. pii: S1369-5266(25)00072-X. [Epub ahead of print]86 102758

Asymmetrical cell division in brown algae: How far can we take the paradigm?

Bénédicte Charrier.

Asymmetrical cell division (ACD) is considered to be the major event leading to cellular differentiation, a crucial step in the development of multicellular organisms. However, when exactly a cell or tissue is considered differentiated is unclear. Focusing on brown algae, this review highlights the different cell division events during embryogenesis and in meristematic cells that establish symmetries or asymmetries in the resulting growing tissues. These examples show that global mechanisms at the embryo or stem cell level can act after and beyond the initial cell division event, which may therefore be less important. Therefore, this review suggests that the use of the term ACD should be restricted to cases where the different cellular functions 1) are characterised at the most comprehensive level possible and 2) are a direct consequence of cell division.

DOI: https://doi.org/10.1016/j.pbi.2025.102758