Sgo1 recruits PP2A to chromosomes to ensure sister chromatid bi-orientation in mitosis

Abstract

Sister chromatid bi-orientation on the mitotic spindle is essential for proper chromosome segregation. Defects in bi-orientation are sensed and corrected to prevent chromosome mis-segregation and aneuploidy. This response depends on the adaptor protein Sgo1, which associates with pericentromeric chromatin in mitosis. The mechanisms underlying Sgo1 function and regulation are unclear. Here, we show that Sgo1 is an anaphase-promoting complex/cyclosome (APC/C) substrate in budding yeast (Saccharomyces cerevisiae), and that its mitotic destruction depends on an unusual D-box-related sequence motif near its Cterminus. We find that the removal of Sgo1 from chromosomes before anaphase is not dependent on its destruction, but rather on other mechanisms responsive to tension between sister chromatids. Additionally, we find that Sgo1 recruits the protein phosphatase 2A (PP2A) isoform containing Rts1 to the pericentromeric region prior to bi-orientation, and that artificial recruitment of Rts1 to this region of a single chromosome is sufficient to perform the function of Sgo1 on that chromosome. We conclude that in early mitosis, Sgo1 associates transiently with pericentromeric chromatin to promote biorientation, in large part by recruiting the Rts1 isoform of PP2A.

Identification of Tension Sensing Motif of Histone H3 inSaccharomyces cerevisiaeand Its Regulation by Histone Modifying Enzymes

“…It is possible that Shugoshin proteins participate in the detection and/or correction of attachment error. Consistently, evidence has been presented for the biorientation-dependent removal of Shugoshin from pericentromeres (Eshleman and Morgan 2014;Nerusheva et al 2014), suggesting that retaining this protein at centromeres and pericentromeres may be a crucial element that keeps the spindle assembly checkpoint at an "on" state before the establishment of biorientation. However, how Shugoshin interacts with SAC remains an open question.…”

“…Centromeric recruitment of Shugoshin depends critically on the phosphorylation of Ser121 of H2A by the Bub1p kinase, as well as several heterochromatic marks at the pericentromeres (Kiburz et al 2005;Fernius and Hardwick 2007;Yamagishi et al 2008;Kawashima et al 2010). Genetic and biochemical experiments revealed that Shugoshin interacts with Ipl1p, the kinase subunit of the chromosomal passenger complex (Campbell and Desai 2013;Ng et al 2013), protein phosphatase 2A (PP2A) (Tang et al 2006;Xu et al 2009;Tanno et al 2010;Liu et al 2013a,b;Eshleman and Morgan 2014), and cohesion (Liu et al 2013b). It is possible that Shugoshin proteins participate in the detection and/or correction of attachment error.…”

Substrate Recognition by the Cdh1 Destruction Box Receptor Is a General Requirement for APC/CCdh1-mediated Proteolysis

“…These include GXEN in Xenopus Xkid (18), the A box or DAD motif (RXLXPSN) in Xenopus Aurora A (19,20), the O-box (PASPLTEKNAK, essential residues underlined) in Drosophila ORC1 (21), LXEXXXXN in Saccharomyces cerevisiae Spo13 (22), LLK in human Claspin (23), the CRY-box in mouse Cdc20 (24), NKSEN in budding yeast Sgo1 (25), and the ABBA motif, FX(I/V/L)(F/Y/H)X(D/E), in human cyclin A, Bub1, and budding yeast Clb5 (26,27). Only the ABBA motif has a known binding site on the co-activator WD40 domains (12,28).…”

Premature Silencing of the Spindle Assembly Checkpoint Is Prevented by the Bub1-H2A-Sgo1-PP2A Axis in Saccharomyces cerevisiae

“…We found that deletion of the Bub1 kinase domain or mutation of the Bub1 phosphorylation site in H2A leads to premature SAC silencing, without compromising SAC activation. Sgo1 interacts with protein phosphatase PP2A Rts1 (Riedel et al 2006;Eshleman and Morgan 2014), and we found that deletion of RTS1 also led to premature SAC silencing. In addition, mutation of the H2A or PP2A Rts1 binding motif in Sgo1 causes anaphase entry in the presence of tensionless chromosome attachment.…”