The structural flexibility of MAD1 facilitates the assembly of the Mitotic Checkpoint Complex.

The spindle assembly checkpoint (SAC) safeguards the genome during cell division by generating an effector molecule known as the Mitotic Checkpoint Complex (MCC). The MCC comprises two subcomplexes: BUBR1:BUB3 and CDC20:MAD2, and the formation of CDC20:MAD2 is the rate-limiting step during MCC assembly. Recent studies show that the rate of CDC20:MAD2 formation is significantly accelerated by the cooperative binding of CDC20 to the SAC proteins MAD1 and BUB1.

CDC20 assists its catalytic incorporation in the mitotic checkpoint complex.

Open (O) and closed (C) topologies of HORMA-domain proteins are respectively associated with inactive and active states of fundamental cellular pathways. The HORMA protein O-MAD2 converts to C-MAD2 upon binding CDC20. This is rate limiting for assembly of the mitotic checkpoint complex (MCC), the effector of a checkpoint required for mitotic fidelity.

Electroporated recombinant proteins as tools for in vivo functional complementation, imaging and chemical biology.

Delivery of native or chemically modified recombinant proteins into mammalian cells shows promise for functional investigations and various technological applications, but concerns that sub-cellular localization and functional integrity of delivered proteins may be affected remain high. Here, we surveyed batch electroporation as a delivery tool for single polypeptides and multi-subunit protein assemblies of the kinetochore, a spatially confined and well-studied subcellular structure. After electroporation into human cells, recombinant fluorescent Ndc80 and Mis12 multi-subunit complexes exhibited native localization, physically interacted with endogenous binding partners, and functionally complemented depleted endogenous counterparts to promote mitotic checkpoint signaling and chromosome segregation.

Mapping Cell Membrane Fluctuations Reveals Their Active Regulation and Transient Heterogeneities.

Shape fluctuations of the plasma membrane occur in all cells, are incessant, and are proposed to affect membrane functioning. Although studies show how membrane fluctuations are affected by cellular activity in adherent cells, their spatial regulation and the corresponding change in membrane mechanics remain unclear. In this article, we study how ATP-driven activities and actomyosin cytoskeleton impact basal membrane fluctuations in adherent cells.