Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

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Gene Review:

BFA1 - Bfa1p

Saccharomyces cerevisiae

Wang, Y., Hu, F., Ro, H.S., Pereira, G., Kim, J., et al.

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High impact information on BFA1

PP2A(Cdc55) downregulation also promotes phosphorylation of Bfa1, contributing to activation of the "mitotic exit network" that sustains Cdc14 as Cdk activity declines [1].
How the Bfa1/Bub2 complex is regulated is not well understood [2].
During most of the cell cycle, Tem1 function is antagonized by a GTPase-activating protein complex, Bfa1/Bub2 [2].
Cdc5 phosphorylates Bfa1 and acts to antagonize Bfa1 function to promote mitotic exit [2].
Bfa1 is regulated by multiple cell cycle checkpoints [2].

Biological context of BFA1

Both Bfa1 and Bub2 localize to spindle poles, and overexpression of Bfa1 arrests the cell cycle in anaphase [3].
We propose that Bfa1/Bub2 checkpoint pathway functions as a universal checkpoint in G2/M that prevents CDK inactivation in response to cell-cycle delay in G2/M [4].
The C-terminal 184 amino acids of Bfa1p (Bfa1-D8(391-574)) contained the entire capacity of Bfa1p to generate mitotic arrest in response to spindle damage, spindle misorientation, and DNA damage [5].
In addition, the viability of cdc5-2 delta bfa1 cells was not reduced by BFA1(E438K), suggesting that Cdc5p also regulates Bfa1p to activate mitotic exit by other mechanism(s), besides phosphorylation [6].
Thus, in vivo inactivation of Bfa1-Bub2 by Cdc5 would have a positive regulatory effect by increasing levels of Tem1-GTP so stimulating exit from mitosis [7].

Anatomical context of BFA1

Thus, SPBs are able to sense cytoplasmic microtubule properties and regulate the Bfa1p-Bub2p GAP accordingly [8].

Physical interactions of BFA1

Coimmunoprecipitation and in vitro binding studies indicate that Bfa1 binds strongly to Tem1 independently of Bub2 [9].
The Bfa1/Bub2 GAP complex comprises a universal checkpoint required to prevent mitotic exit [4].
We have isolated a novel Bfa1p interacting protein named Ibd2p in the budding yeast Saccharomyces cerevisiae [10].
Regulation of the Bub2/Bfa1 GAP complex by Cdc5 and cell cycle checkpoints [2].

Regulatory relationships of BFA1

This effect is Bfa1 dependent and can be suppressed by high Tem1 levels [11].
These data indicate that Cdc14p activates the MEN in early anaphase but later inactivates it through Bfa1p dephosphorylation and so restricts MEN activity to a short period in anaphase [12].

Other interactions of BFA1

Here, we have demonstrated that introduction of bfa1 Delta suppresses the growth defects associated with the cdc5-1 mutation significantly better than that of bub2 Delta, suggesting that Bfa1 may have a previously uncharacterized role in this pathway [9].
In the spindle checkpoint pathway, this is accomplished through Bfa1/Bub2, a heteromeric GTPase-activating protein (GAP) that inhibits Clb degradation by keeping the G protein Tem1 inactive [3-5] [4].
We also found that the delay in mitotic exit in mutants with misoriented spindles depended on BUB2 and BFA1, but not on MAD2 [4].
Following spindle checkpoint activation, the cell cycle phosphorylation of Bfa1 and Lte1 is protracted and some species are accentuated [13].
Regulation of the Bfa1p-Bub2p complex at spindle pole bodies by the cell cycle phosphatase Cdc14p [12].

References

Downregulation of PP2A(Cdc55) phosphatase by separase initiates mitotic exit in budding yeast. Queralt, E., Lehane, C., Novak, B., Uhlmann, F. Cell (2006)
Regulation of the Bub2/Bfa1 GAP complex by Cdc5 and cell cycle checkpoints. Hu, F., Wang, Y., Liu, D., Li, Y., Qin, J., Elledge, S.J. Cell (2001)
Bifurcation of the mitotic checkpoint pathway in budding yeast. Li, R. Proc. Natl. Acad. Sci. U.S.A. (1999)
The Bfa1/Bub2 GAP complex comprises a universal checkpoint required to prevent mitotic exit. Wang, Y., Hu, F., Elledge, S.J. Curr. Biol. (2000)
The C-terminus of Bfa1p in budding yeast is essential to induce mitotic arrest in response to diverse checkpoint-activating signals. Kim, J., Jeong, J., Song, K. Genes Cells (2004)
The study of Bfa1p(E438K) suggests that Bfa1 control the mitotic exit network in different mechanisms depending on different checkpoint-activating signals. Kim, J., Song, K. Mol. Cells (2006)
In vitro regulation of budding yeast Bfa1/Bub2 GAP activity by Cdc5. Geymonat, M., Spanos, A., Walker, P.A., Johnston, L.H., Sedgwick, S.G. J. Biol. Chem. (2003)
Modes of spindle pole body inheritance and segregation of the Bfa1p-Bub2p checkpoint protein complex. Pereira, G., Tanaka, T.U., Nasmyth, K., Schiebel, E. EMBO J. (2001)
Bfa1 can regulate Tem1 function independently of Bub2 in the mitotic exit network of Saccharomyces cerevisiae. Ro, H.S., Song, S., Lee, K.S. Proc. Natl. Acad. Sci. U.S.A. (2002)
IBD2 encodes a novel component of the Bub2p-dependent spindle checkpoint in the budding yeast Saccharomyces cerevisiae. Hwang, H.S., Song, K. Genetics (2002)
Disappearance of the budding yeast Bub2-Bfa1 complex from the mother-bound spindle pole contributes to mitotic exit. Fraschini, R., D'Ambrosio, C., Venturetti, M., Lucchini, G., Piatti, S. J. Cell Biol. (2006)
Regulation of the Bfa1p-Bub2p complex at spindle pole bodies by the cell cycle phosphatase Cdc14p. Pereira, G., Manson, C., Grindlay, J., Schiebel, E. J. Cell Biol. (2002)
The Bub2-dependent mitotic pathway in yeast acts every cell cycle and regulates cytokinesis. Lee, S.E., Jensen, S., Frenz, L.M., Johnson, A.L., Fesquet, D., Johnston, L.H. J. Cell. Sci. (2001)