Haspin Modulates the G2/M Transition Delay in Response to Polarization Failures in Budding Yeast

Abstract

Symmetry breaking by cellular polarization is an exquisite requirement for the cell-cycle of Saccharomyces cerevisiae cells, as it allows bud emergence and growth. This process is based on the formation of polarity clusters at the incipient bud site, first, and the bud tip later in the cell-cycle, that overall promote bud emission and growth. Given the extreme relevance of this process, a surveillance mechanism, known as the morphogenesis checkpoint, has evolved to coordinate the formation of the bud and cell cycle progression, delaying mitosis in the presence of morphogenetic problems. The atypical protein kinase haspin is responsible for histone H3-T3 phosphorylation and, in yeast, for resolution of polarity clusters in mitosis. Here, we report a novel role for haspin in the regulation of the morphogenesis checkpoint in response to polarity insults. Particularly, we show that cells lacking the haspin ortholog Alk1 fail to achieve sustained checkpoint activation and enter mitosis even in the absence of a bud. In alk1Δ cells, we report a reduced phosphorylation of Cdc28-Y19, which stems from a premature activation of the Mih1 phosphatase. Overall, the data presented in this work define yeast haspin as a novel regulator of the morphogenesis checkpoint in Saccharomyces cerevisiae, where it monitors polarity establishment and it couples bud emergence to the G2/M cell cycle transition.

Distinct Aurora B pools at the inner centromere and kinetochore have different contributions to meiotic and mitotic chromosome segregation

“…We found that there were no major defects in chromatin segregation in the individual single mutants that disrupt one pool of Ipl1 Aurora B kinetochore localization (Figure 4E). However, depletion of both Ctf19 and Bub3 resulted in a strong defect in chromatin segregation, with 47% of cells with uneven chromatin masses between the mother and the bud, which agrees with previous findings in the literature (Garcia-Rodriguez et al, 2019). Loss of the haspin and Ndc10 pathways, combined with Bub3-depletion did not display an enhanced defect (Figure 4E).…”

“…However, whether the haspin kinase pathway is functional for Ipl1 Aurora B inner centromere recruitment in budding yeast is currently debated (Campbell and Desai, 2013;Edgerton et al, 2016;Galli et al, 2020;Nespoli et al, 2006;Panigada et al, 2013). In addition, budding yeast have two additional pathways that control Ipl1 Aurora B localization, through the inner centromere protein Ndc10 and through the COMA complex (Cho and Harrison, 2011;Fischbock-Halwachs et al, 2019;Garcia-Rodriguez et al, 2019;Yoon and Carbon, 1999). Whether these four pathways contribute to Aurora B's role in error correction during meiosis compared to mitosis has not been tested.…”

“…In the budding yeast-specific Ndc10 pathway, the centromere-binding protein Ndc10 can interact with the CPC component Bir1 to bring the CPC to the inner centromere (Cho and Harrison, 2011;Yoon and Carbon, 1999). Finally, in the budding yeast-specific COMA complex (containing Ctf19, Okp1, Mcm21, and Ame1) pathway, Sli15 binds to Ctf19 to help localize Ipl1 Aurora B (Fischbock-Halwachs et al, 2019;Garcia-Rodriguez et al, 2019). Whether each of these kinetochore-localized pools of Aurora B contributes to error correction of kinetochore-microtubule attachment in meiosis is unknown.…”

“…Studies from mammalian cells lines, Xenopus egg extracts, budding yeast, and fission yeast have revealed two important pathways for Aurora B localization, the Bub1/Bub3 pathway and the haspin kinase pathway (Edgerton et al, 2016; Jeyaprakash et al, 2011; Kawashima et al, 2010; Kelly et al, 2010; Wang et al, 2010; Yamagishi et al, 2010). However, whether the haspin kinase pathway is functional for Ipl1 Aurora B inner centromere recruitment in budding yeast is currently debated (Campbell and Desai, 2013; Edgerton et al, 2016; Galli et al, 2020; Nespoli et al, 2006; Panigada et al, 2013). In addition, budding yeast have two additional pathways that control Ipl1 Aurora B localization, through the inner centromere protein Ndc10 and through the COMA complex (Cho and Harrison, 2011; Fischbock-Halwachs et al, 2019; Garcia-Rodriguez et al, 2019; Yoon and Carbon, 1999).…”

Phosphorylation of H3-Thr3 by Haspin Is Required for Primary Cilia Regulation

“…Accordingly, loss of H3-Thr3 phosphorylation results in chromosomal segregation defects [ 1 , 5 ]. Other roles for Haspin have been reported in the coupling of cell-cycle progression to polarization dynamics [ 6 , 7 , 8 , 9 ], chromatid cohesion [ 10 , 11 ], organization of microtubule organizing centers (MTOCs) during murine meiosis [ 12 ], and asymmetrical histone inheritance [ 13 ] and migration [ 14 ], and Haspin inhibitors have a well-established anticancer activity [ 14 , 15 ].…”