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Spindle checkpoint activation at meiosis I advances anaphase II onset via meiosis-specific APC/C regulation.

Yamamoto A, Kitamura K, Hihara D, Hirose Y, Katsuyama S, Hiraoka Y - J. Cell Biol. (2008)

Bottom Line: Furthermore, anaphase onset was advanced and the SAC effect was reduced at meiosis II.The advancement of anaphase onset depended on a meiosis-specific, Cdc20-related factor, Fzr1/Mfr1, which contributed to anaphase cyclin decline and anaphase onset and was inefficiently inhibited by the SAC.Our findings show that impacts of SAC activation are not confined to a single division at meiosis due to meiosis-specific APC/C regulation, which has probably been evolved for execution of two meiotic divisions.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Shizuoka University, Suruga-ku, Shizuoka 422-8529, Japan. sayamam@ipc.shizuoka.ac.jp

ABSTRACT
During mitosis, the spindle assembly checkpoint (SAC) inhibits the Cdc20-activated anaphase-promoting complex/cyclosome (APC/C(Cdc20)), which promotes protein degradation, and delays anaphase onset to ensure accurate chromosome segregation. However, the SAC function in meiotic anaphase regulation is poorly understood. Here, we examined the SAC function in fission yeast meiosis. As in mitosis, a SAC factor, Mad2, delayed anaphase onset via Slp1 (fission yeast Cdc20) when chromosomes attach to the spindle improperly. However, when the SAC delayed anaphase I, the interval between meiosis I and II shortened. Furthermore, anaphase onset was advanced and the SAC effect was reduced at meiosis II. The advancement of anaphase onset depended on a meiosis-specific, Cdc20-related factor, Fzr1/Mfr1, which contributed to anaphase cyclin decline and anaphase onset and was inefficiently inhibited by the SAC. Our findings show that impacts of SAC activation are not confined to a single division at meiosis due to meiosis-specific APC/C regulation, which has probably been evolved for execution of two meiotic divisions.

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Dynamics of the chromosome and the spindle at MII in rec8 and clr4 mutants. (A) Behavior of sister centromeres (white and red arrowheads) and the SPB (yellow) at MII in rec8 (top left and right) and clr4 (bottom left and right) mutants. The graph shows changes in the SPB-cen (D1 and D2) and SPB-SPB (D3) distances. PI, phase I; PII, phase II; PIII, phase III. Bar, 2 μm. (B) Mean distances of centromeres at phase II. More than eight pairs of centromeres were examined for each analysis. (C) Changes in spindle length at MII in the rec8 (left) and clr4 (right) mutants. Graphs show kinetics of two MII spindles in the same cell. Dotted lines in graphs show boundaries of the spindle phases. (D) Duration of the spindle phases at MII. (E) Duration of MI, MII, and the MI–MII interval. Wt, wild type. Error bars indicate standard deviation.
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fig3: Dynamics of the chromosome and the spindle at MII in rec8 and clr4 mutants. (A) Behavior of sister centromeres (white and red arrowheads) and the SPB (yellow) at MII in rec8 (top left and right) and clr4 (bottom left and right) mutants. The graph shows changes in the SPB-cen (D1 and D2) and SPB-SPB (D3) distances. PI, phase I; PII, phase II; PIII, phase III. Bar, 2 μm. (B) Mean distances of centromeres at phase II. More than eight pairs of centromeres were examined for each analysis. (C) Changes in spindle length at MII in the rec8 (left) and clr4 (right) mutants. Graphs show kinetics of two MII spindles in the same cell. Dotted lines in graphs show boundaries of the spindle phases. (D) Duration of the spindle phases at MII. (E) Duration of MI, MII, and the MI–MII interval. Wt, wild type. Error bars indicate standard deviation.

Mentions: Analysis of the chromosome dynamics confirmed premature dissociation and improper spindle attachments of sister chromatids in these mutants. In rec8, sister chromatids underwent equational segregation at MI (not depicted; Watanabe and Nurse, 1999) and remained separated at MII (Fig. 3 A, top, rec8), whereas in clr4, although chromosomes underwent normal segregation at MI (not depicted), sister chromatids prematurely dissociated at MII (Fig. 3 A, bottom, clr4). As a consequence, preanaphase sister centromere distances increased by approximately twofold on average in both mutants (Fig. 3 B). Sister centromeres oscillated between the two poles independently of each other in rec8 (Fig. 3 A, top, rec8, PII; and Fig. 3 A, top right, D1 and D2), whereas they oscillated coordinately with apparent anaphase A movement thereafter in clr4 (Fig. 3 A, bottom, clr4, PII; Fig. 3 A, bottom right, D1 and D2; and Table S2). Despite this difference, chromosomes attach to the spindle improperly, as shown by sister centromere segregation to the same pole (43.8% in 16 cells for rec8 and 21.4% in 14 cells for clr4; Fig. 3 A, top, 34 min) and centromere lagging (37.5% for rec8 and 25.0% for clr4; Fig. 3 A, top right, rec8), and the parameters of centromere movements were similar (Table S2).


Spindle checkpoint activation at meiosis I advances anaphase II onset via meiosis-specific APC/C regulation.

Yamamoto A, Kitamura K, Hihara D, Hirose Y, Katsuyama S, Hiraoka Y - J. Cell Biol. (2008)

Dynamics of the chromosome and the spindle at MII in rec8 and clr4 mutants. (A) Behavior of sister centromeres (white and red arrowheads) and the SPB (yellow) at MII in rec8 (top left and right) and clr4 (bottom left and right) mutants. The graph shows changes in the SPB-cen (D1 and D2) and SPB-SPB (D3) distances. PI, phase I; PII, phase II; PIII, phase III. Bar, 2 μm. (B) Mean distances of centromeres at phase II. More than eight pairs of centromeres were examined for each analysis. (C) Changes in spindle length at MII in the rec8 (left) and clr4 (right) mutants. Graphs show kinetics of two MII spindles in the same cell. Dotted lines in graphs show boundaries of the spindle phases. (D) Duration of the spindle phases at MII. (E) Duration of MI, MII, and the MI–MII interval. Wt, wild type. Error bars indicate standard deviation.
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fig3: Dynamics of the chromosome and the spindle at MII in rec8 and clr4 mutants. (A) Behavior of sister centromeres (white and red arrowheads) and the SPB (yellow) at MII in rec8 (top left and right) and clr4 (bottom left and right) mutants. The graph shows changes in the SPB-cen (D1 and D2) and SPB-SPB (D3) distances. PI, phase I; PII, phase II; PIII, phase III. Bar, 2 μm. (B) Mean distances of centromeres at phase II. More than eight pairs of centromeres were examined for each analysis. (C) Changes in spindle length at MII in the rec8 (left) and clr4 (right) mutants. Graphs show kinetics of two MII spindles in the same cell. Dotted lines in graphs show boundaries of the spindle phases. (D) Duration of the spindle phases at MII. (E) Duration of MI, MII, and the MI–MII interval. Wt, wild type. Error bars indicate standard deviation.
Mentions: Analysis of the chromosome dynamics confirmed premature dissociation and improper spindle attachments of sister chromatids in these mutants. In rec8, sister chromatids underwent equational segregation at MI (not depicted; Watanabe and Nurse, 1999) and remained separated at MII (Fig. 3 A, top, rec8), whereas in clr4, although chromosomes underwent normal segregation at MI (not depicted), sister chromatids prematurely dissociated at MII (Fig. 3 A, bottom, clr4). As a consequence, preanaphase sister centromere distances increased by approximately twofold on average in both mutants (Fig. 3 B). Sister centromeres oscillated between the two poles independently of each other in rec8 (Fig. 3 A, top, rec8, PII; and Fig. 3 A, top right, D1 and D2), whereas they oscillated coordinately with apparent anaphase A movement thereafter in clr4 (Fig. 3 A, bottom, clr4, PII; Fig. 3 A, bottom right, D1 and D2; and Table S2). Despite this difference, chromosomes attach to the spindle improperly, as shown by sister centromere segregation to the same pole (43.8% in 16 cells for rec8 and 21.4% in 14 cells for clr4; Fig. 3 A, top, 34 min) and centromere lagging (37.5% for rec8 and 25.0% for clr4; Fig. 3 A, top right, rec8), and the parameters of centromere movements were similar (Table S2).

Bottom Line: Furthermore, anaphase onset was advanced and the SAC effect was reduced at meiosis II.The advancement of anaphase onset depended on a meiosis-specific, Cdc20-related factor, Fzr1/Mfr1, which contributed to anaphase cyclin decline and anaphase onset and was inefficiently inhibited by the SAC.Our findings show that impacts of SAC activation are not confined to a single division at meiosis due to meiosis-specific APC/C regulation, which has probably been evolved for execution of two meiotic divisions.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Shizuoka University, Suruga-ku, Shizuoka 422-8529, Japan. sayamam@ipc.shizuoka.ac.jp

ABSTRACT
During mitosis, the spindle assembly checkpoint (SAC) inhibits the Cdc20-activated anaphase-promoting complex/cyclosome (APC/C(Cdc20)), which promotes protein degradation, and delays anaphase onset to ensure accurate chromosome segregation. However, the SAC function in meiotic anaphase regulation is poorly understood. Here, we examined the SAC function in fission yeast meiosis. As in mitosis, a SAC factor, Mad2, delayed anaphase onset via Slp1 (fission yeast Cdc20) when chromosomes attach to the spindle improperly. However, when the SAC delayed anaphase I, the interval between meiosis I and II shortened. Furthermore, anaphase onset was advanced and the SAC effect was reduced at meiosis II. The advancement of anaphase onset depended on a meiosis-specific, Cdc20-related factor, Fzr1/Mfr1, which contributed to anaphase cyclin decline and anaphase onset and was inefficiently inhibited by the SAC. Our findings show that impacts of SAC activation are not confined to a single division at meiosis due to meiosis-specific APC/C regulation, which has probably been evolved for execution of two meiotic divisions.

Show MeSH