Abstract
Microtubules are essential for a variety of fundamental cellular processes such as organelle positioning and control of cell shape. Schizosaccharomyces pombe is an ideal organism for studying the function and organization of microtubules into bundles in interphase cells. Using light microscopy and electron tomography we analyzed the bundle organization of interphase microtubules in S. pombe. We show that cells lacking ase1p and klp2p still contain microtubule bundles. In addition, we show that ase1p is the major determinant of inter-microtubule spacing in interphase bundles since ase1 deleted cells have an inter-microtubule spacing that differs from that observed in wild-type cells. We then identified dis1p, a XMAP215 homologue, as factor that promotes the stabilization of microtubule bundles. In wild-type cells dis1p partially co-localized with ase1p at regions of microtubule overlap. In cells deleted for ase1 and klp2, dis1p accumulated at the overlap regions of interphase microtubule bundles. In cells lacking all three proteins, both microtubule bundling and inter-microtubule spacing were further reduced, suggesting that Dis1p contributes to interphase microtubule bundling.
Highlights
The formation of microtubule (MT) arrays and the organization of individual MTs is essential for diverse cellular functions such as spindle biogenesis [1], regulation of neuronal growth [2] and organelle positioning [3,4]
We observed a 30% decrease in the number of regions in interphase microtubule assemblies’’ (IMAs) containing fluorescence intensity twice or more that of single MTs (Table 1)
In this work we investigated the role of several proteins in the formation of IMAs in S. pombe
Summary
The formation of microtubule (MT) arrays and the organization of individual MTs is essential for diverse cellular functions such as spindle biogenesis [1], regulation of neuronal growth [2] and organelle positioning [3,4]. The fission yeast Schizosaccharomyces pombe is a well-established model organism for studying the control of cell polarity, MT dynamics and spindle assembly [6,7,8]. Most MTs are associated with each other in bundles, a few individual MTs are present [9]. Since it is difficult to unambiguously distinguish between single MTs and bundled MTs using fluorescence microscopy, both arrangements are generally termed ‘‘interphase microtubule assemblies’’ (IMAs) [6,10]. IMAs are essential for determining the sites of growth in S. pombe [7] and defects in their organization lead to cells with abnormal morphologies [8,11,12,13]
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