Nature Cell Biology4, 816 - 820 (2002)
Published online: 30 September 2002; | doi:10.1038/ncb861
Astral microtubules monitor metaphase spindle alignment in fission yeast
Snezhana Oliferenko
& Mohan K. Balasubramanian
Temasek Life Sciences Laboratory and Institute of Molecular Agrobiology, 1 Research Link, The National University of Singapore, 117604 Singapore
Correspondence should be addressed to Snezhana Oliferenko snejana@tll.org.sg
Segregating genetic material along the longest axis of the cell ensures that there is a sufficient distance between daughter chromosomes at the point of cytokinesis. Monitoring the orientation of the mitotic spindle can be subjected to cell cycle controls. In the fission yeast Schizosaccharomyces pombe, the existence of such a cell-cycle checkpoint has been proposed to delay the metaphase to anaphase transition when spindle poles are not properly oriented with respect to the actomyosin ring1. Here we show, by using a fission yeast mutant compromised in its assembly of astral microtubules, that in the absence of astral microtubules short metaphase spindles are unable to orient themselves with respect to the long axis of the cell and are delayed in spindle elongation. This astral defect engages a spindle orientation checkpoint because deletion of the transcription factor Atf1, which is involved in maintaining this checkpoint, allows misaligned asterless metaphase spindles to elongate. We propose that astral microtubules are involved directly in monitoring orientation of the metaphase spindle and in controlling the timing of elongation in fission yeast.
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