Histone H3 and H3-like CENP-A-specific chaperone. Promotes delivery and incorporation of CENP-A in centromeric chromatin, probably by escorting nascent CENP-A to CENP-A chromatin assembly factors. Required for central core silencing and normal chromosome segregation. Interacts with cnp1, hht1, hht2 and hht3; has a preference for CENP-A (cnp1) over histone H3 (hht1/2/3). Belongs to the NASP family.