A stable microtubule array drives fission yeast polarity reestablishment upon quiescence exit.
Bottom Line: Astonishingly, MTs are also stabilized and rearranged into a novel antiparallel bundle associated with the spindle pole body, named Q-MT bundle.Finally and importantly, we reveal that Q-MT bundle elongation is involved in polarity reestablishment upon quiescence exit and thereby the efficient return to the proliferative state.Our work demonstrates that quiescent S. pombe cells assemble specific cytoskeleton structures that improve the swiftness of the transition back to proliferation.
Affiliation: Université de Bordeaux, Institut de Biochimie et Génétique Cellulaires, 33000 Bordeaux, France Centre National de la Recherche Scientifique, UMR5095 Bordeaux, 33077 Bordeaux, France.Show MeSH
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Mentions: In our experimental conditions, glucose exhaustion is responsible for cell entry into quiescence (Fig. S4 A). When quiescent cells were refed with rich medium, the Q-MT bundle rapidly elongated from both extremities, a proof of the MT antiparallel arrangement within the Q-MT bundle (Fig. 5 A and Fig. S4, B and C). In ∼5 min, dynamic MTs polymerizing from the Q-MT bundle touched the cell poles. Of note, tracking SPB movement upon quiescence exit clearly demonstrated that the Q-MT bundle was attached to the SPB (Fig. S4 E). The MT plus end–tracking protein Alp14, although immobile onto the Q-MT bundle in quiescence (Fig. S4 F), was found at the tip of elongating MTs upon quiescence exit (Figs. 5 B and S4 F). In contrast, the minus end–associated protein Mto2 stayed immobile on the elongating Q-MT bundle (Fig. S4 G). Later (>15 min), new MT bundles were assembled de novo at the nuclear periphery. Interestingly, as for other quiescent cell-specific structures (Laporte et al., 2011, 2013), the sole addition of glucose onto quiescent cells trigged both Q-MT bundle elongation and assembly of new interphase MT bundles at the nuclear periphery (Fig. 5 A). Importantly, these two MT rearrangements occurred even if de novo protein synthesis was inhibited by cycloheximide (CHX; Fig. 5 A). Yet, as expected, cells treated with CHX did not elongate upon refeeding (Fig. S4 D). This experiment demonstrated that the MT cytoskeleton remodeling upon quiescence exit did not need de novo tubulin synthesis.
Affiliation: Université de Bordeaux, Institut de Biochimie et Génétique Cellulaires, 33000 Bordeaux, France Centre National de la Recherche Scientifique, UMR5095 Bordeaux, 33077 Bordeaux, France.