string: 1999), each binds Cdc2p (and presumably Pop2p), is phosphorylated by the Cdc2p kinase in vitro and in vivo and inhibits Cdc2p activity in vitro (Correa-Bordes and Nurse 1995; Elsasser et al. 1996; Martin-Castellanos and Moreno 1996; Brown et al. 1997; Jallepalli et al. 1997; Benito et al. 1998; Lopez-Girona et al. 1998).