Limits...
Tension sensing by Aurora B kinase is independent of survivin-based centromere localization.

Campbell CS, Desai A - Nature (2013)

Bottom Line: Unlike wild-type Sli15, truncated Sli15 localizes to pre-anaphase spindle microtubules.Premature targeting of full-length Sli15 to microtubules by preventing Cdk1 (also known as Cdc28) phosphorylation also suppresses the inviability of Bir1 deletion.These results suggest that activation of Aurora B kinase by clustering either on chromatin or on microtubules is sufficient for chromosome biorientation.

View Article: PubMed Central - PubMed

Affiliation: Ludwig Institute for Cancer Research and Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California 92037, USA.

ABSTRACT
Accurate segregation of the replicated genome requires chromosome biorientation on the spindle. Biorientation is ensured by Aurora B kinase (Ipl1), a member of the four-subunit chromosomal passenger complex (CPC). Localization of the CPC to the inner centromere is central to the current model for how tension ensures chromosome biorientation: kinetochore-spindle attachments that are not under tension remain close to the inner centromere and are destabilized by Aurora B phosphorylation, whereas kinetochores under tension are pulled away from the influence of Aurora B, stabilizing their microtubule attachments. Here we show that an engineered truncation of the Sli15 (known as INCENP in humans) subunit of budding yeast CPC that eliminates association with the inner centromere nevertheless supports proper chromosome segregation during both mitosis and meiosis. Truncated Sli15 suppresses the deletion phenotypes of the inner-centromere-targeting proteins survivin (Bir1), borealin (Nbl1), Bub1 and Sgo1 (ref. 6). Unlike wild-type Sli15, truncated Sli15 localizes to pre-anaphase spindle microtubules. Premature targeting of full-length Sli15 to microtubules by preventing Cdk1 (also known as Cdc28) phosphorylation also suppresses the inviability of Bir1 deletion. These results suggest that activation of Aurora B kinase by clustering either on chromatin or on microtubules is sufficient for chromosome biorientation.

Show MeSH

Related in: MedlinePlus

sli15ΔNT suppresses mutants in the Bir1-dependent CPC targeting pathway but is synthetically lethal with genes implicated in centromere cohesion(a) Schematic of the CPC targeting mechanism involving Bub1 kinase and Sgo1.(b) Suppression of sgo1Δ and bub1Δ growth phenotypes by sli15ΔNT. Compromised growth of sgo1Δ on benomyl is also suppressed by sli15ΔNT.(c) Viability following transient nocodazole treatment of cells of the indicated genotypes. The average of 2 to 4 experiments is shown; error bars represent standard error. WT and sli15ΔNT measurements are the same as in Fig. 2f.(d) Tetrad analysis showing no synthetic defect for cells that are triple mutants for sli15ΔNT alk1Δ and alk1Δ.(e) Tetrad analysis showing synthetic lethality of sli15ΔNT and mcm21Δ. Similar results were observed for ctf19Δ (Fig. S2b).(f) Summary of genetic interactions exhibited by sli15ΔNT. A positive genetic interaction (green) indicates suppression; negative genetic interaction (red) indicates synthetic lethality/sickness and neutral interaction (black) indicates lack of a synthetic phenotype.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3644022&req=5

Figure 3: sli15ΔNT suppresses mutants in the Bir1-dependent CPC targeting pathway but is synthetically lethal with genes implicated in centromere cohesion(a) Schematic of the CPC targeting mechanism involving Bub1 kinase and Sgo1.(b) Suppression of sgo1Δ and bub1Δ growth phenotypes by sli15ΔNT. Compromised growth of sgo1Δ on benomyl is also suppressed by sli15ΔNT.(c) Viability following transient nocodazole treatment of cells of the indicated genotypes. The average of 2 to 4 experiments is shown; error bars represent standard error. WT and sli15ΔNT measurements are the same as in Fig. 2f.(d) Tetrad analysis showing no synthetic defect for cells that are triple mutants for sli15ΔNT alk1Δ and alk1Δ.(e) Tetrad analysis showing synthetic lethality of sli15ΔNT and mcm21Δ. Similar results were observed for ctf19Δ (Fig. S2b).(f) Summary of genetic interactions exhibited by sli15ΔNT. A positive genetic interaction (green) indicates suppression; negative genetic interaction (red) indicates synthetic lethality/sickness and neutral interaction (black) indicates lack of a synthetic phenotype.

Mentions: We next tested if Sli15ΔNT also bypasses mutations in the Bir1 localization pathway. Bir1-dependent targeting of the CPC to the inner centromere involves recognition of phosphorylated histone H2a by Sgo1 (Fig. 3a). Chromosome biorientation errors in bub1Δ and sgo1Δ mutants lead to severe growth defects, sensitivity to benomyl, and difficulty correcting defective attachments following nocodazole washout18. sli15ΔNT suppressed the severe growth defect of both bub1Δ and sgo1Δ cells (Fig. 3b); in addition, the benomyl sensitivity, the rapid loss of viability following transient nocodazole treatment, and the chromosome missegregation of sgo1Δ cells were also suppressed (Fig. 3b,c; Fig. S1c). The benomyl sensitivity of bub1Δ was not suppressed as the spindle checkpoint function of Bub1 is independent of its role in CPC localization. While Haspin kinases contribute to CPC targeting in other organisms via creating a binding site on centromeric chromatin for Survivin, deletion of the two Haspin homologues in budding yeast had no growth phenotype on their own or in combination with sli15ΔNT (Fig. 3d).


Tension sensing by Aurora B kinase is independent of survivin-based centromere localization.

Campbell CS, Desai A - Nature (2013)

sli15ΔNT suppresses mutants in the Bir1-dependent CPC targeting pathway but is synthetically lethal with genes implicated in centromere cohesion(a) Schematic of the CPC targeting mechanism involving Bub1 kinase and Sgo1.(b) Suppression of sgo1Δ and bub1Δ growth phenotypes by sli15ΔNT. Compromised growth of sgo1Δ on benomyl is also suppressed by sli15ΔNT.(c) Viability following transient nocodazole treatment of cells of the indicated genotypes. The average of 2 to 4 experiments is shown; error bars represent standard error. WT and sli15ΔNT measurements are the same as in Fig. 2f.(d) Tetrad analysis showing no synthetic defect for cells that are triple mutants for sli15ΔNT alk1Δ and alk1Δ.(e) Tetrad analysis showing synthetic lethality of sli15ΔNT and mcm21Δ. Similar results were observed for ctf19Δ (Fig. S2b).(f) Summary of genetic interactions exhibited by sli15ΔNT. A positive genetic interaction (green) indicates suppression; negative genetic interaction (red) indicates synthetic lethality/sickness and neutral interaction (black) indicates lack of a synthetic phenotype.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3644022&req=5

Figure 3: sli15ΔNT suppresses mutants in the Bir1-dependent CPC targeting pathway but is synthetically lethal with genes implicated in centromere cohesion(a) Schematic of the CPC targeting mechanism involving Bub1 kinase and Sgo1.(b) Suppression of sgo1Δ and bub1Δ growth phenotypes by sli15ΔNT. Compromised growth of sgo1Δ on benomyl is also suppressed by sli15ΔNT.(c) Viability following transient nocodazole treatment of cells of the indicated genotypes. The average of 2 to 4 experiments is shown; error bars represent standard error. WT and sli15ΔNT measurements are the same as in Fig. 2f.(d) Tetrad analysis showing no synthetic defect for cells that are triple mutants for sli15ΔNT alk1Δ and alk1Δ.(e) Tetrad analysis showing synthetic lethality of sli15ΔNT and mcm21Δ. Similar results were observed for ctf19Δ (Fig. S2b).(f) Summary of genetic interactions exhibited by sli15ΔNT. A positive genetic interaction (green) indicates suppression; negative genetic interaction (red) indicates synthetic lethality/sickness and neutral interaction (black) indicates lack of a synthetic phenotype.
Mentions: We next tested if Sli15ΔNT also bypasses mutations in the Bir1 localization pathway. Bir1-dependent targeting of the CPC to the inner centromere involves recognition of phosphorylated histone H2a by Sgo1 (Fig. 3a). Chromosome biorientation errors in bub1Δ and sgo1Δ mutants lead to severe growth defects, sensitivity to benomyl, and difficulty correcting defective attachments following nocodazole washout18. sli15ΔNT suppressed the severe growth defect of both bub1Δ and sgo1Δ cells (Fig. 3b); in addition, the benomyl sensitivity, the rapid loss of viability following transient nocodazole treatment, and the chromosome missegregation of sgo1Δ cells were also suppressed (Fig. 3b,c; Fig. S1c). The benomyl sensitivity of bub1Δ was not suppressed as the spindle checkpoint function of Bub1 is independent of its role in CPC localization. While Haspin kinases contribute to CPC targeting in other organisms via creating a binding site on centromeric chromatin for Survivin, deletion of the two Haspin homologues in budding yeast had no growth phenotype on their own or in combination with sli15ΔNT (Fig. 3d).

Bottom Line: Unlike wild-type Sli15, truncated Sli15 localizes to pre-anaphase spindle microtubules.Premature targeting of full-length Sli15 to microtubules by preventing Cdk1 (also known as Cdc28) phosphorylation also suppresses the inviability of Bir1 deletion.These results suggest that activation of Aurora B kinase by clustering either on chromatin or on microtubules is sufficient for chromosome biorientation.

View Article: PubMed Central - PubMed

Affiliation: Ludwig Institute for Cancer Research and Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California 92037, USA.

ABSTRACT
Accurate segregation of the replicated genome requires chromosome biorientation on the spindle. Biorientation is ensured by Aurora B kinase (Ipl1), a member of the four-subunit chromosomal passenger complex (CPC). Localization of the CPC to the inner centromere is central to the current model for how tension ensures chromosome biorientation: kinetochore-spindle attachments that are not under tension remain close to the inner centromere and are destabilized by Aurora B phosphorylation, whereas kinetochores under tension are pulled away from the influence of Aurora B, stabilizing their microtubule attachments. Here we show that an engineered truncation of the Sli15 (known as INCENP in humans) subunit of budding yeast CPC that eliminates association with the inner centromere nevertheless supports proper chromosome segregation during both mitosis and meiosis. Truncated Sli15 suppresses the deletion phenotypes of the inner-centromere-targeting proteins survivin (Bir1), borealin (Nbl1), Bub1 and Sgo1 (ref. 6). Unlike wild-type Sli15, truncated Sli15 localizes to pre-anaphase spindle microtubules. Premature targeting of full-length Sli15 to microtubules by preventing Cdk1 (also known as Cdc28) phosphorylation also suppresses the inviability of Bir1 deletion. These results suggest that activation of Aurora B kinase by clustering either on chromatin or on microtubules is sufficient for chromosome biorientation.

Show MeSH
Related in: MedlinePlus