BFA1 is a non-essential gene whose product is involved in the spindle checkpoint (3). The spindle checkpoint delays the onset of anaphase in cells with defects in mitotic spindle assembly or in the attachment of chromosomes to the spindle microtubules (see 4 for review; reference 5 describes defects detected by the checkpoint). The checkpoint works by inhibiting the activity of the anaphase promoting complex, thereby preventing the degradation of several cell cycle regulators (4). Like other spindle checkpoint mutants, bfa1 null mutants are sensitive to benomyl and cannot delay cell division in response to spindle depolymerization. Overexpression of BFA1 causes cells to arrest in anaphase (3). Bfa1p and Bub2p localize to the spindle pole body, and appear to act in a branch of the spindle checkpoint pathway that may prevent cytokinesis prior to chromosome segregation (6, 7, 8, 3). Cdh1p, an activator of the anaphase promoting complex, and the protein kinase Dbf2p are likely targets of Bub2p and Bfa1p (6, 7). Genetic evidence suggests that the Bub2p-Bfa1p branch of the spindle checkpoint pathway is distinct from that involving Bub1p, Bub3p, Mad1p, Mad2p, Mad3p, and Mps1p, which may prevent premature chromosome disjunction (4, 6, 7, 8, 3). The C-terminus of Bfa1p has sequence similarity to Byr4p, a negative regulator of cytokinesis in S. pombe. Unlike Byr4p, Bfa1p does not appear to play a role in cytokinesis in the absence of spindle damage (3).

Last updated: 2000-04-04