MT plus-end-tracking non-motor protein; binds MTs, stabilizes interpolar MT plus ends, facilitates spindle MT polymerization and produces an outward force on spindle poles; required for mitotic spindle integrity; binds detached kinetochores (KTs) and upon phosphorylation by Mps1p recruits Slk19p, promoting capture and clustering; regulates spindle stability; relocalizes to MTs when captured KTs reach a spindle pole; localizes to spindles, spindles poles, and detached KTs; human CLASP1/2 homolog