Comparison of self-assembly properties of coat proteins and implications for RZZ–Spindly. (A) The units of self-assembly in COPI, COPII, and Clathrin cages are proteins consisting of an N-terminal β-propeller followed by an α-solenoid. These units often form oligomers (e.g., the inverted tetramers of Sec13–31), which further self-assemble to create finite structures like cages. Whether the kinetochore fibrous corona reflects an ordered assembly of RZZ–Spindly complexes is currently unclear. Kinetochores may act to nucleate self-assembly of cytosolic RZZ–Spindly units and to promote the formation of crescents. (B) Summary of interactions and pathways discussed in this paper.