TY - JOUR T1 - Optogenetic control of PRC1 reveals its role in kinetochore alignment at the metaphase plate JF - bioRxiv DO - 10.1101/865394 SP - 865394 AU - Mihaela Jagrić AU - Patrik Risteski AU - Jelena Martinčić AU - Ana Milas AU - Iva M. Tolić Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/12/04/865394.abstract N2 - During metaphase, chromosome position at the spindle equator is mainly regulated by the forces exerted by kinetochore microtubules. However, the role of forces arising from mechanical coupling between sister k-fibers and bridging fibers, whose antiparallel microtubules are crosslinked by protein regulator of cytokinesis 1 (PRC1), in chromosome alignment is unknown. Here we develop an optogenetic approach for acute removal of PRC1 and show that PRC1 promotes kinetochore alignment. PRC1 removal resulted in reduction of bridging fibers and straightening of outermost kinetochore fibers. The inter-kinetochore distance decreased, the metaphase plate widened, and lagging kinetochores appeared, suggesting the role of PRC1 in regulating forces on kinetochores. MKLP1/kinesin-6 was lost from the spindle together with PRC1, whereas Kif4A/kinesin-4 remained on chromosomes and CLASP1, Kif18A, and CENP-E on the ends of kinetochore fibers. In conclusion, our optogenetic experiments indicate that in metaphase PRC1, by mechanically coupling bridging and kinetochore fibers, regulates spindle mechanics and forces acting on kinetochores, promoting kinetochore alignment. ER -