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: Tubulin binds GTP and can hydrolyze this nucleotide. The influence of the tubulin nucleotide status on MT dynamics in vivo is still a mater of debate (Kueh and Mitchison, 2009). We have analyzed the GTP concentration variation upon entry into quiescence after carbon exhaustion using high pressure ionic chromatography and observed a drastic decrease of the intracellular pool of this nucleotide (Fig. 3 A). Mycophenolic acid (MPA) is a drug that specifically inhibits inosine-5′-monophosphate dehydrogenase, the enzyme that catalyzes the conversion of inosine-5′-monophosphate into guanosine-5′-monophosphate (Allison and Eugui, 2000), the GTP precursor. As in other organisms (Qiu et al., 2000), MPA treatment of proliferating S. pombe cells caused GTP depletion (Fig. 3 B). The GTP drop was reversed by addition of guanine in the medium, demonstrating the specificity of MPA treatment (Escobar-Henriques et al., 2001). Interestingly, MPA treatment did not significantly affect MT growth or shrinkage rates (Fig. 3 C) nor the MT catastrophe and rescue frequencies (not depicted), excluding the possibility that MT stabilization would be an immediate consequence of GTP depletion upon quiescence entry.
Affiliation: Université de Bordeaux, Institut de Biochimie et Génétique Cellulaires, 33000 Bordeaux, France Centre National de la Recherche Scientifique, UMR5095 Bordeaux, 33077 Bordeaux, France.