Proposed to be part of the KMN network incorporating the MIS12 complex and NDC80 complex that is required for establishing the kinetochore-microtubule interface that aids in chromosome segregation during meiotic and mitotic cell division. Appears to function downstream of hcp-3 (CENP-A) and hcp-4 (CENP-C) in the kinetochore assembly hierarchy. Has a role in the correct localization of spdl-1 and the RZZ complex that is composed of rod-1, czw-1 and zwl-1. Required for the recruitment of spindle-assembly checkpoint components bub-1 and mdf-1/2 to unattached kinetochores (By similarity). Interacts with hcp-3 and hcp-4 to form a complex. Interacts with hcp-4, him-10, kbp-3, kbp-4, kbp-5, knl-3, and ndc-80. Interacts with kbp-1, kbp-2 and mis-12; which make up the MIS12 complex. Also found on the surface of chromosomes. Subcellular localization dependent on expression of hcp-3, hcp-4 and knl-3. During anaphase of meiosis I, localized also to spindle-associated rod-shaped structures which depends on zwl-1 (By similarity). The N-terminus contains a number of repeats which contribute additively to bub-1 recruitment to unattached kinetochores. The repeats are not required for localization to kinetochores (By similarity).