Background of the antigen
spindle microtubules. The checkpoint works by inhibiting the activity of the anaphase promoting complex, thereby preventing the degradation of several cell cycle regulators. Like other spindle checkpoint mutants, MAD1 loss-of-function mutants are sensitive to benomyl and cannot delay cell division in response to spindle depolymerization. Mad1p becomes hyperphosphorylated upon spindle depolymerization.