Cdc5-dependent asymmetric localization of Bfa1 fine-tunes timely mitotic exit

Junwon Kim, Guangming Luo, Young Yil Bahk, Kiwon Song

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

In budding yeast, the major regulator of the mitotic exit network (MEN) is Tem1, a GTPase, which is inhibited by the GTPase-activating protein (GAP), Bfa1/Bub2. Asymmetric Bfa1 localization to the bud-directed spindle pole body (SPB) during metaphase also controls mitotic exit, but the molecular mechanism and function of this localization are not well understood, particularly in unperturbed cells. We identified four novel Cdc5 target residues within the Bfa1 C-terminus: 452S, 453S, 454S, and 559S. A Bfa1 mutant in which all of these residues had been changed to alanine (Bfa1 4A) persisted on both SPBs at anaphase and was hypo-phosphorylated, despite retaining its GAP activity for Tem1. A Bfa1 phospho-mimetic mutant in which all of these residues were switched to aspartate (Bfa1 4D) always localized asymmetrically to the SPB. These observations demonstrate that asymmetric localization of Bfa1 is tightly linked to its Cdc5-dependent phosphorylation, but not to its GAP activity. Consistent with this, in kinase-defective cdc5-2 cells Bfa1 was not phosphorylated and localized to both SPBs, whereas Bfa1 4D was asymmetrically localized. BFA1 4A cells progressed through anaphase normally but displayed delayed mitotic exit in unperturbed cell cycles, while BFA1 4D cells underwent mitotic exit with the same kinetics as wild-type cells. We suggest that Cdc5 induces the asymmetric distribution of Bfa1 to the bud-directed SPB independently of Bfa1 GAP activity at anaphase and that Bfa1 asymmetry fine-tunes the timing of MEN activation in unperturbed cell cycles.

Original languageEnglish
Article numbere1002450
JournalPLoS Genetics
Volume8
Issue number1
DOIs
Publication statusPublished - 2012 Jan 1

Fingerprint

GTPase-activating proteins
GTPase-Activating Proteins
Spindle Pole Bodies
spindle pole body
Anaphase
anaphase
protein
bud
cells
cell cycle
Cell Cycle
buds
mutants
Saccharomycetales
GTP Phosphohydrolases
yeast
guanosinetriphosphatase
aspartic acid
asymmetry
Metaphase

All Science Journal Classification (ASJC) codes

  • Genetics
  • Molecular Biology
  • Ecology, Evolution, Behavior and Systematics
  • Cancer Research
  • Genetics(clinical)

Cite this

Kim, Junwon ; Luo, Guangming ; Bahk, Young Yil ; Song, Kiwon. / Cdc5-dependent asymmetric localization of Bfa1 fine-tunes timely mitotic exit. In: PLoS Genetics. 2012 ; Vol. 8, No. 1.
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Cdc5-dependent asymmetric localization of Bfa1 fine-tunes timely mitotic exit. / Kim, Junwon; Luo, Guangming; Bahk, Young Yil; Song, Kiwon.

In: PLoS Genetics, Vol. 8, No. 1, e1002450, 01.01.2012.

Research output: Contribution to journalArticle

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T1 - Cdc5-dependent asymmetric localization of Bfa1 fine-tunes timely mitotic exit

AU - Kim, Junwon

AU - Luo, Guangming

AU - Bahk, Young Yil

AU - Song, Kiwon

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N2 - In budding yeast, the major regulator of the mitotic exit network (MEN) is Tem1, a GTPase, which is inhibited by the GTPase-activating protein (GAP), Bfa1/Bub2. Asymmetric Bfa1 localization to the bud-directed spindle pole body (SPB) during metaphase also controls mitotic exit, but the molecular mechanism and function of this localization are not well understood, particularly in unperturbed cells. We identified four novel Cdc5 target residues within the Bfa1 C-terminus: 452S, 453S, 454S, and 559S. A Bfa1 mutant in which all of these residues had been changed to alanine (Bfa1 4A) persisted on both SPBs at anaphase and was hypo-phosphorylated, despite retaining its GAP activity for Tem1. A Bfa1 phospho-mimetic mutant in which all of these residues were switched to aspartate (Bfa1 4D) always localized asymmetrically to the SPB. These observations demonstrate that asymmetric localization of Bfa1 is tightly linked to its Cdc5-dependent phosphorylation, but not to its GAP activity. Consistent with this, in kinase-defective cdc5-2 cells Bfa1 was not phosphorylated and localized to both SPBs, whereas Bfa1 4D was asymmetrically localized. BFA1 4A cells progressed through anaphase normally but displayed delayed mitotic exit in unperturbed cell cycles, while BFA1 4D cells underwent mitotic exit with the same kinetics as wild-type cells. We suggest that Cdc5 induces the asymmetric distribution of Bfa1 to the bud-directed SPB independently of Bfa1 GAP activity at anaphase and that Bfa1 asymmetry fine-tunes the timing of MEN activation in unperturbed cell cycles.

AB - In budding yeast, the major regulator of the mitotic exit network (MEN) is Tem1, a GTPase, which is inhibited by the GTPase-activating protein (GAP), Bfa1/Bub2. Asymmetric Bfa1 localization to the bud-directed spindle pole body (SPB) during metaphase also controls mitotic exit, but the molecular mechanism and function of this localization are not well understood, particularly in unperturbed cells. We identified four novel Cdc5 target residues within the Bfa1 C-terminus: 452S, 453S, 454S, and 559S. A Bfa1 mutant in which all of these residues had been changed to alanine (Bfa1 4A) persisted on both SPBs at anaphase and was hypo-phosphorylated, despite retaining its GAP activity for Tem1. A Bfa1 phospho-mimetic mutant in which all of these residues were switched to aspartate (Bfa1 4D) always localized asymmetrically to the SPB. These observations demonstrate that asymmetric localization of Bfa1 is tightly linked to its Cdc5-dependent phosphorylation, but not to its GAP activity. Consistent with this, in kinase-defective cdc5-2 cells Bfa1 was not phosphorylated and localized to both SPBs, whereas Bfa1 4D was asymmetrically localized. BFA1 4A cells progressed through anaphase normally but displayed delayed mitotic exit in unperturbed cell cycles, while BFA1 4D cells underwent mitotic exit with the same kinetics as wild-type cells. We suggest that Cdc5 induces the asymmetric distribution of Bfa1 to the bud-directed SPB independently of Bfa1 GAP activity at anaphase and that Bfa1 asymmetry fine-tunes the timing of MEN activation in unperturbed cell cycles.

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