Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.
PLoS One. 2010 Oct 21;5(10):e13553. doi: 10.1371/journal.pone.0013553.
Ser172 of β tubulin is an important residue that is mutated in a human brain disease and phosphorylated by the cyclin-dependent kinase Cdk1 in mammalian cells. To examine the role of this residue, we used the yeast S. cerevisiae as a model and produced two different mutations (S172A and S172E) of the conserved Ser172 in the yeast β tubulin Tub2p. The two mutants showed impaired cell growth on benomyl-containing medium and at cold temperatures, altered microtubule (MT) dynamics, and altered nucleus positioning and segregation. When cytoplasmic MT effectors Dyn1p or Kar9p were deleted in S172A and S172E mutants, cells were viable but presented increased ploidy. Furthermore, the two β tubulin mutations exhibited synthetic lethal interactions with Bik1p, Bim1p or Kar3p, which are effectors of cytoplasmic and spindle MTs. In the absence of Mad2p-dependent spindle checkpoint, both mutations are deleterious. These findings show the importance of Ser172 for the correct function of both cytoplasmic and spindle MTs and for normal cell division.
β微管蛋白 Ser172 是一个重要的残基，在人类脑部疾病中发生突变，并在哺乳动物细胞中被细胞周期蛋白依赖性激酶 Cdk1 磷酸化。为了研究该残基的作用，我们使用酵母 S. cerevisiae 作为模型，在酵母β微管蛋白 Tub2p 中产生了保守的 Ser172 的两个不同突变（S172A 和 S172E）。这两个突变体在含有苯并咪唑的培养基和低温下显示出细胞生长受损、微管（MT）动力学改变以及核定位和分离改变。当在 S172A 和 S172E 突变体中缺失细胞质 MT 效应物 Dyn1p 或 Kar9p 时，细胞仍然存活，但出现了较高的倍性。此外，这两个β微管蛋白突变与 Bik1p、Bim1p 或 Kar3p 表现出合成致死相互作用，这些蛋白是细胞质和纺锤体 MT 的效应物。在没有 Mad2p 依赖性纺锤体检查点的情况下，这两个突变都是有害的。这些发现表明 Ser172 对于细胞质和纺锤体 MT 的正确功能以及正常细胞分裂都非常重要。
