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The chromosomal passenger complex controls the function of endosomal sorting complex required for transport-III Snf7 proteins during cytokinesis.

Capalbo L, Montembault E, Takeda T, Bassi ZI, Glover DM, D'Avino PP - Open Biol (2012)

Bottom Line: Here, we show that the CPC subunit Borealin interacts directly with the Snf7 components of ESCRT-III in both Drosophila and human cells.Moreover, we find that the CPC's catalytic subunit, Aurora B kinase, phosphorylates one of the three human Snf7 paralogues-CHMP4C-in its C-terminal tail, a region known to regulate its ability to form polymers and associate with membranes.Phosphorylation at these sites appears essential for CHMP4C function because their mutation leads to cytokinesis defects.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.

ABSTRACT
Cytokinesis controls the proper segregation of nuclear and cytoplasmic materials at the end of cell division. The chromosomal passenger complex (CPC) has been proposed to monitor the final separation of the two daughter cells at the end of cytokinesis in order to prevent cell abscission in the presence of DNA at the cleavage site, but the precise molecular basis for this is unclear. Recent studies indicate that abscission could be mediated by the assembly of filaments comprising components of the endosomal sorting complex required for transport-III (ESCRT-III). Here, we show that the CPC subunit Borealin interacts directly with the Snf7 components of ESCRT-III in both Drosophila and human cells. Moreover, we find that the CPC's catalytic subunit, Aurora B kinase, phosphorylates one of the three human Snf7 paralogues-CHMP4C-in its C-terminal tail, a region known to regulate its ability to form polymers and associate with membranes. Phosphorylation at these sites appears essential for CHMP4C function because their mutation leads to cytokinesis defects. We propose that CPC controls abscission timing through inhibition of ESCRT-III Snf7 polymerization and membrane association using two concurrent mechanisms: interaction of its Borealin component with Snf7 proteins and phosphorylation of CHMP4C by Aurora B.

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Related in: MedlinePlus

Model for Aurora B-mediated regulation of CHMP4C during cytokinesis. (a) Schematic of CHMP4C indicating the position of the Aurora B target sites. (b) Interaction with Borealin and phosphorylation by Aurora B keep CHMP4C in its ‘closed’ state at the midbody before abscission. (c) When CPC is no longer at the midbody, CHMP4C can convert into its ‘open’ state and form membrane-associated polymers that mediate abscission.
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RSOB120070F7: Model for Aurora B-mediated regulation of CHMP4C during cytokinesis. (a) Schematic of CHMP4C indicating the position of the Aurora B target sites. (b) Interaction with Borealin and phosphorylation by Aurora B keep CHMP4C in its ‘closed’ state at the midbody before abscission. (c) When CPC is no longer at the midbody, CHMP4C can convert into its ‘open’ state and form membrane-associated polymers that mediate abscission.

Mentions: Our findings identify a novel, evolutionarily conserved interaction between CPC and ESCRT-III Snf7 components. In both Drosophila and human cells, the CPC Borealin subunit interacts directly with Shrb/CHMP4 proteins, and in human cells Aurora B phosphorylates the C-terminal tail of CHMP4C. The latter mechanism seems to have evolved specifically for the human CHMP4C protein because the three residues phosphorylated by Aurora B—S210, S214 and S215—are not present in the other two human paralogues and Shrb (figure 2). Consistent with this, Aurora B weakly phosphorylated CHMP4A, CHMP4B and Shrb in vitro (figure 5, and data not shown). The lack of conservation of phosphorylation sites between orthologues is not uncommon; for example, the Polo-like kinase-1 phosphorylation sites in PRC1, a protein required for bundling the central spindle, are not conserved in its Drosophila orthologue Fascetto [26,27]. Our results suggest that the CHMP4C phosphorylation status does not affect its ability to accumulate at the midbody but it does impair its function during cytokinesis (figure 6). Interestingly, the serines phosphorylated by Aurora B are located in a region linking the C-terminal-most two alpha-helices of CHMP4C (figure 7). This region has been found to be essential for regulating the activity of many ESCRT-III proteins in various biological processes, including viral budding and cytokinesis [8,24]. Current models propose that ESCRT-III proteins cycle between a default auto-inhibitory or ‘closed’ status and an ‘open’, active form (figure 7) [24,28]. In the ‘closed’ status, the basic and acidic halves of the ESCRT-III protein are tightly associated, and the protein is soluble and does not interact with other components of the ESCRT machinery and the membrane. In the ‘open’ form, the two halves of the ESCRT-III protein dissociate, and the protein forms polymers that associate with the membrane and other ESCRT-III components (figure 7) [24]. The C-terminal tail of ESCRT-III proteins, including the last α-helix and the linker region, has been proposed to play a key role in the transition from the closed to the open status, possibly through its interaction with other regulatory factors [24,28]. Our results suggest that Aurora B phosphorylation could prevent the conversion of CHMP4C from a closed, auto-inhibitory status into an open, active status (figure 7), possibly by inhibiting the association of CHMP4C with some other regulatory partner(s).Figure 7.


The chromosomal passenger complex controls the function of endosomal sorting complex required for transport-III Snf7 proteins during cytokinesis.

Capalbo L, Montembault E, Takeda T, Bassi ZI, Glover DM, D'Avino PP - Open Biol (2012)

Model for Aurora B-mediated regulation of CHMP4C during cytokinesis. (a) Schematic of CHMP4C indicating the position of the Aurora B target sites. (b) Interaction with Borealin and phosphorylation by Aurora B keep CHMP4C in its ‘closed’ state at the midbody before abscission. (c) When CPC is no longer at the midbody, CHMP4C can convert into its ‘open’ state and form membrane-associated polymers that mediate abscission.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376741&req=5

RSOB120070F7: Model for Aurora B-mediated regulation of CHMP4C during cytokinesis. (a) Schematic of CHMP4C indicating the position of the Aurora B target sites. (b) Interaction with Borealin and phosphorylation by Aurora B keep CHMP4C in its ‘closed’ state at the midbody before abscission. (c) When CPC is no longer at the midbody, CHMP4C can convert into its ‘open’ state and form membrane-associated polymers that mediate abscission.
Mentions: Our findings identify a novel, evolutionarily conserved interaction between CPC and ESCRT-III Snf7 components. In both Drosophila and human cells, the CPC Borealin subunit interacts directly with Shrb/CHMP4 proteins, and in human cells Aurora B phosphorylates the C-terminal tail of CHMP4C. The latter mechanism seems to have evolved specifically for the human CHMP4C protein because the three residues phosphorylated by Aurora B—S210, S214 and S215—are not present in the other two human paralogues and Shrb (figure 2). Consistent with this, Aurora B weakly phosphorylated CHMP4A, CHMP4B and Shrb in vitro (figure 5, and data not shown). The lack of conservation of phosphorylation sites between orthologues is not uncommon; for example, the Polo-like kinase-1 phosphorylation sites in PRC1, a protein required for bundling the central spindle, are not conserved in its Drosophila orthologue Fascetto [26,27]. Our results suggest that the CHMP4C phosphorylation status does not affect its ability to accumulate at the midbody but it does impair its function during cytokinesis (figure 6). Interestingly, the serines phosphorylated by Aurora B are located in a region linking the C-terminal-most two alpha-helices of CHMP4C (figure 7). This region has been found to be essential for regulating the activity of many ESCRT-III proteins in various biological processes, including viral budding and cytokinesis [8,24]. Current models propose that ESCRT-III proteins cycle between a default auto-inhibitory or ‘closed’ status and an ‘open’, active form (figure 7) [24,28]. In the ‘closed’ status, the basic and acidic halves of the ESCRT-III protein are tightly associated, and the protein is soluble and does not interact with other components of the ESCRT machinery and the membrane. In the ‘open’ form, the two halves of the ESCRT-III protein dissociate, and the protein forms polymers that associate with the membrane and other ESCRT-III components (figure 7) [24]. The C-terminal tail of ESCRT-III proteins, including the last α-helix and the linker region, has been proposed to play a key role in the transition from the closed to the open status, possibly through its interaction with other regulatory factors [24,28]. Our results suggest that Aurora B phosphorylation could prevent the conversion of CHMP4C from a closed, auto-inhibitory status into an open, active status (figure 7), possibly by inhibiting the association of CHMP4C with some other regulatory partner(s).Figure 7.

Bottom Line: Here, we show that the CPC subunit Borealin interacts directly with the Snf7 components of ESCRT-III in both Drosophila and human cells.Moreover, we find that the CPC's catalytic subunit, Aurora B kinase, phosphorylates one of the three human Snf7 paralogues-CHMP4C-in its C-terminal tail, a region known to regulate its ability to form polymers and associate with membranes.Phosphorylation at these sites appears essential for CHMP4C function because their mutation leads to cytokinesis defects.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.

ABSTRACT
Cytokinesis controls the proper segregation of nuclear and cytoplasmic materials at the end of cell division. The chromosomal passenger complex (CPC) has been proposed to monitor the final separation of the two daughter cells at the end of cytokinesis in order to prevent cell abscission in the presence of DNA at the cleavage site, but the precise molecular basis for this is unclear. Recent studies indicate that abscission could be mediated by the assembly of filaments comprising components of the endosomal sorting complex required for transport-III (ESCRT-III). Here, we show that the CPC subunit Borealin interacts directly with the Snf7 components of ESCRT-III in both Drosophila and human cells. Moreover, we find that the CPC's catalytic subunit, Aurora B kinase, phosphorylates one of the three human Snf7 paralogues-CHMP4C-in its C-terminal tail, a region known to regulate its ability to form polymers and associate with membranes. Phosphorylation at these sites appears essential for CHMP4C function because their mutation leads to cytokinesis defects. We propose that CPC controls abscission timing through inhibition of ESCRT-III Snf7 polymerization and membrane association using two concurrent mechanisms: interaction of its Borealin component with Snf7 proteins and phosphorylation of CHMP4C by Aurora B.

Show MeSH
Related in: MedlinePlus