Tripartite Chromatin Localization of Budding Yeast Shugoshin Involves Higher-Ordered Architecture of Mitotic Chromosomes

Abstract

The spindle assembly checkpoint (SAC) is key to faithful segregation of chromosomes. One requirement that satisfies SAC is appropriate tension between sister chromatids at the metaphase-anaphase juncture. Proper tension generated by poleward pulling of mitotic spindles signals biorientation of the underlying chromosome. In the budding yeast, the tension status is monitored by the conserved Shugoshin protein, Sgo1p, and the tension sensing motif (TSM) of histone H3. ChIP-seq reveals a unique TSM-dependent, tripartite domain of Sgo1p in each mitotic chromosome. This domain consists of one centromeric and two flanking peaks 3 – 4 kb away, present exclusively in mitosis. Strikingly, this trident motif coincides with cohesin localization, but only at the centromere and the two immediate adjacent loci, despite that cohesin is enriched at numerous regions throughout mitotic chromosomes. Chromosome conformation capture assays reveal apparent looping at the centromeric and pericentric regions. The TSM-Sgo1p-cohesin triad is therefore at the center stage of higher-ordered chromatin architecture for error-free segregation.

Surprising phenotypic diversity of cancer-associated mutations of Gly 34 in the histone H3 tail

“…We note that an interesting functional link between H3 and Shugoshin has also been made in budding yeast, where the homolog of Sgo2, SGO1 has been shown to bind histone H3. Although not reliant on G34 or K36 residues of H3, SGO1 binds a ‘tension-sensing motif’ at residues 42–45 on H3, which is necessary for Sgo1 recruitment to centromeres and for efficient chromosome segregation during mitosis ( Deng and Kuo, 2018 ; Luo et al, 2016 ). Intriguingly in this system, the histone acetyltransferase Gcn5 is important for ensuring efficient chromosome segregation when the tension sensing motif is damaged ( Buehl et al, 2018 ; Luo et al, 2016 ).…”

Non-essential kinetochore proteins contribute to meiotic chromosome condensation through polo-like kinase

“…Besides protecting the pericentromeric cohesin in meiosis I, Sgo1 (Shugoshin) has a role in mitotic chromosome condensation (Kruitwagen et al, 2018) through condensin loading at pericentromeric region (Peplowska et al, 2014). It has also been reported that in the absence of Ctf19c proteins, Iml3 and Chl4, the Sgo1 localization becomes compromised at the chromatin both in mitosis (Deng et al, 2018) and meiosis (Kiburz et al, 2005). To investigate if Ctf19, unlike the peripheral Ctf19c components Iml3 and Chl4, differs in recruiting Sgo1 on the chromatin between mitosis and meiosis which may cause the differential effect on condensation, we analyzed the localization of Sgo1-EGFP in mitosis (metaphase) and meiosis (metaphase I) in presence or absence of Ctf19.…”

Shugoshin Regulates Cohesin, Kinetochore-Microtubule Attachments, and Chromosomal Instability

“…In syntelic attachments, both sister kinetochores are captured by microtubules of the same pole. Moreover, wrong monotelic and syntelic attachments before anaphase can lead to aneuploidy [Deng and Kuo, 2018]. Therefore, correcting inappropriate kineto- chore-microtubule attachments before entry into anaphase is crucial for appropriate chromosome division.…”

“…However, before the late trigger, the early decline or loss of cohesin level leads to chromosome segregation errors [Tsutsumi et al, 2014], and the occurrence of unpaired sister chromatids is one of the direct reasons for the premature separation of sister chromatid aneuploidy [Mikwar et al, 2020]. In addition, sister chromatids are captured by the same pole before AI of meiosis, and homologous chromosomes cross-connected are captured by microtubules from two poles of the spindle because the tension produced by the centromeric cohesin resisting the pulling force between sister chromatids can stabilize kinetochore-microtubule connections [Kiburz et al, 2008;Clift and Marston, 2011;Marston, 2015;Miyazaki et al, 2017b;Deng and Kuo, 2018]. At the beginning of AI, the meiosis-specific subunit REC8 at the chromosome arm is cleaved by separase, but the cohesin at the centromeres is protected until metaphase II, which explains homologous chromosome segregation and sister chromatid non-segregation in AI [Marston, 2015;Miyazaki et al, 2017].…”