string: …(Pankov et al., 1990; Yen et al., 1991; Casiano et al., 1993), the inner centromere proteins (INCENPs) (Cooke et al., 1987; Earnshaw and Cooke, 1991; Mackay et al., 1993), and the nuclear mitotic apparatus (NuMA) proteins (Lydersen and Pettijohn, 1980; Compton et al., 1992; Yang and Snyder, 1992).