| Sil phosphorylation in a Pin 1 binding domain affects the duration of the spindle checkpoint . ^^^ Cell cycle dependent phosphorylation of Sil is required for its interaction with Pin 1 , a regulator of mitosis . ^^^ Point mutation of the seven ( S / T ) P sites between amino acids 567 and 760 reduces mitotic phosphorylation of Sil , Pin 1 binding , and spindle checkpoint duration . ^^^ |