Essential component of the spindle apparatus required for spindle positioning and chromosome movement. Acts to recruit or anchor gpr-1/gpr-2 complex to the spindle and cortex. Also involved; directly or indirectly; in cytokinesis and in the coupling of DNA replication; centrosome duplication and mitotic division. {ECO:0000269|PubMed:10629219; ECO:0000269|PubMed:12730122}.