PMID:24558497

Citation	Makrantoni, V, Corbishley, SJ, Rachidi, N, Morrice, NA, Robinson, DA and Stark, MJ (2014) Phosphorylation of Sli15 by Ipl1 is important for proper CPC localization and chromosome stability in Saccharomyces cerevisiae. PLoS ONE 9:e89399
Abstract	The chromosomal passenger complex (CPC) is a key regulator of eukaryotic cell division, consisting of the protein kinase Aurora B/Ipl1 in association with its activator (INCENP/Sli15) and two additional proteins (Survivin/Bir1 and Borealin/Nbl1). Here we have identified multiple sites of CPC autophosphorylation on yeast Sli15 that are located within its central microtubule-binding domain and examined the functional significance of their phosphorylation by Ipl1 through mutation of these sites, either to non-phosphorylatable alanine (sli15-20A) or to acidic residues to mimic constitutive phosphorylation (sli15-20D). Both mutant sli15 alleles confer chromosome instability, but this is mediated neither by changes in the capacity of Sli15 to activate Ipl1 kinase nor by decreased efficiency of chromosome biorientation, a key process in cell division that requires CPC function. Instead, we find that mimicking constitutive phosphorylation of Sli15 on the Ipl1 phosphorylation sites causes delocalization of the CPC in metaphase, whereas blocking phosphorylation of Sli15 on the Ipl1 sites drives excessive localization of Sli15 to the mitotic spindle in pre-anaphase cells. Consistent with these results, direct interaction of Sli15 with microtubules in vitro is greatly reduced either following phosphorylation by Ipl1 or when constitutive phosphorylation at the Ipl1-dependent phosphorylation sites is mimicked by aspartate or glutamate substitutions. Furthermore, we find that mimicking Ipl1 phosphorylation of Sli15 interferes with the 'tension checkpoint'--the CPC-dependent mechanism through which cells activate the spindle assembly checkpoint to delay anaphase in the absence of tension on kinetochore-microtubule attachments. Ipl1-dependent phosphorylation of Sli15 therefore inhibits its association with microtubules both in vivo and in vitro and may negatively regulate the tension checkpoint mechanism.
Links	PubMed PMC3928436 Online version:10.1371/journal.pone.0089399
Keywords	Aurora Kinases/metabolism; Carrier Proteins/metabolism; Cell Division/physiology; Chromosomal Instability/physiology; Microscopy, Fluorescence; Microtubule-Associated Proteins/metabolism; Microtubules/metabolism; Multiprotein Complexes/metabolism; Phosphorylation; Saccharomyces cerevisiae/genetics; Saccharomyces cerevisiae/physiology; Saccharomyces cerevisiae Proteins/metabolism; Time-Lapse Imaging
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
YEAST:SLI15		GO:0072686: mitotic spindle	ECO:0000314:		C		Fig. 8 shows sli15 being located on the mitotic spindle. Organism: S. cerevisiae	complete CACAO 12953
YEAST:SLI15		GO:0032147: activation of protein kinase activity	ECO:0000314:		P		Seen in figure 3, Ipl1 is activated by Sli15. Ipl1 is a protein kinase. Therefore, Sli15 activates protein kinase activity. Organism: S. cerevisiae	complete CACAO 12954
YEAST:SLI15		GO:1990023: mitotic spindle midzone	ECO:0000315:		C		Fig. 8 shows sli15 being located on mitotic spindle. However, phosphorylation of Sli15 may both reduce overall microtubule association and bias Sli15 localization towards the poles and away from the mid-zone of the anaphase spindle. Thus WITH OUT phosphorylation, microtubule association is at the mitotic spindle midzone. Organism: S. cerevisiae	complete CACAO 12964
YEAST:IPL1		GO:0018105: peptidyl-serine phosphorylation	ECO:0000314:		P		Table 4 shows phosphorylation sites for Ipl1 phosphorylation sites in Sli15. In this case, Peptidyl-serine phosphorylation is observed. Organism: S. cerevisiae	complete CACAO 12969
YEAST:IPL1		GO:0018107: peptidyl-threonine phosphorylation	ECO:0000314:		P		Table 4 shows phosphorylation sites for Ipl1 phosphorylation sites in Sli15. Thus, in this case, Peptidyl-threonine phosphorylation is observed. Organism: S. cerevisiae	complete CACAO 12970

References

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