A Failsafe for Sensing Chromatid Tension in Mitosis with the Histone H3 Tail inSaccharomyces cerevisiae

Abstract

Mitotic fidelity is ensured by achieving biorientation on all paired chromosomes. The key signal for proper chromosome alignment is the tension between sister chromatids created by opposing poleward force from the spindles. In the budding yeast, the tension-sensing function requires that the Shugoshin protein, Shugoshin 1, be recruited to the centromeres and the neighboring pericentric regions. Concerted actions integrating proteins at centromeres and pericentromeres create highly specific Shugoshin 1 domains on mitotic chromosomes. We have previously reported that an important regulatory region on histone H3, termed the tension-sensing motif (TSM), is responsible for retaining Shugoshin 1 at pericentromeres. The TSM is negatively regulated by the acetyltransferase Gcn5p, but the underlying mechanism was elusive. In this work, we provide evidence that, when the TSM function is impaired, the histone H3 tail adopts a role that complements the damaged TSM to ensure faithful mitosis. This novel function of the H3 tail is controlled by Gcn5p, which targets selective lysine residues. Mutations to K14 and K23 ameliorate the mitotic defects resulting from TSM mutations. The restoration of faithful segregation is accompanied by regaining Shugoshin 1 access to the pericentric regions. Our data reveal a novel pathway for mitotic Shugoshin 1 recruitment and further reinforce the active role played by chromatins during their segregation in mitosis.

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

“…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 ). It is not clear whether Shugoshin proteins in higher organisms show a similar dependence on N-terminal regions of H3 for their localization and whether H3.3-G34R mutation influences their localization.…”

Surprising Phenotypic Diversity of Cancer-associated mutations of Gly 34 in the Histone H3 tail

“…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 Luo, Deng, Buehl, Xu, & Kuo, 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). It is not clear whether Shugoshin proteins in higher organisms show a similar dependence on N-terminal regions of H3 for their localization and whether H3.3-G34R mutation influences their localization.…”

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

“…Our recent findings that Gcn5p acts as a negative regulator for tension sensing motif and Sgo1p functional interaction (L uo et al 2016; B uehl et al 2018) alludes to an intriguing possibility that Gcn5p, acetylated H3, or a downstream effector may prevent Sgo1p from binding to the chromosome arms. ChIP-seq data show a lack of correlation between Gcn5p and these Sgo1p-free valleys in mitosis (Figure 3), arguing against a direct, physical role of Gcn5p.…”

“…The budding yeast Shugoshin, Sgo1p , was first identified as a protector of meiotic cohesin against precocious cleavage ( K itajima et al 2004 ), and later found to be also crucial for cells to activate the SAC in coping with tensionless conditions in mitosis ( I ndjeian et al 2005 ). Expressed in S and M phases of the cell cycle ( I ndjeian et al 2005 ; E shleman and M organ 2014 ), Sgo1p is localized to centromeres and pericentromere ( K iburz et al 2005 ; F ernius and H ardwick 2007 ; K iburz et al 2008 ) without stashing a significant extrachromosomal pool ( B uehl et al 2018 ). Shugoshin is recruited to centromeres by binding to histone H2A phosphorylated by the Bub1 kinase ( K awashima et al 2010 ; L iu et al 2013a ).…”

“…Mutations at K43, G44, or T45 diminish the pericentric localization of Sgo1p and obliterate the cellular response to defects in tension. Restoring pericentric association of Sgo1p by overexpression, via Sgo1p -bromodomain fusion ( L uo et al 2010 ), or by mutating the inhibitory residues K14 or K23 of the H3 tail ( B uehl et al 2018 ) rescues the mitotic defects of these TSM mutations, thus manifesting the pivotal role of Sgo1p retention at the pericentromere. Sgo1p is removed from chromatin after tension is built up in the metaphase ( N erusheva et al 2014 ).…”