PRC1 and kinesin-4, proteins required for cytokinesis, can tag microtubule plus ends
•
Size of plus-end-tags formed by PRC1 and kinesin-4 scales with microtubule length
•
The extended helix-rich PRC1 dimer has distinct kinesin-4- and filament-binding sites
•
Plus-end-tagging depends on PRC1’s interaction with both kinesin-4 and microtubules
Summary
Error-free cell division depends on the assembly of the spindle midzone, a specialized array of overlapping microtubules that emerges between segregating chromosomes during anaphase. The molecular mechanisms by which a subset of dynamic microtubules from the metaphase spindle are selected and organized into a stable midzone array are poorly understood. Here, we show using in vitro reconstitution assays that PRC1 and kinesin-4, two microtubule-associated proteins required for midzone assembly, can tag microtubule plus ends. Remarkably, the size of these tags is proportional to filament length. We determine the crystal structure of the PRC1 homodimer and map the protein-protein interactions needed for tagging microtubule ends. Importantly, length-dependent microtubule plus-end-tagging by PRC1 is also observed in dividing cells. Our findings suggest how biochemically similar microtubules can be differentially marked, based on length, for selective regulation during the formation of specialized arrays, such as those required for cytokinesis.
