Required for the spindle checkpoint attachment response during spindle formation; kinetochore microtubule interactions and chromosome segregation during anaphase. Ark1 activity depends upon cut17 function and phosphorylation. Ark1 with bir1 is required for full-scale association with kinetochores and formation of a complex with mad3. Ark1 is also required for phosphorylation of histone H3 that accompanies chromosome condensation and condensin recruitment to mitotic chromatin. Ark1 with pic1 is required for the execution of cytokinesis. {ECO:0000269|PubMed:11792803; ECO:0000269|PubMed:11950927; ECO:0000269|PubMed:12676091}.