芽殖酵母是衰老研究的一个重要模型。细胞通过在母细胞表面上一个芽的形成而发生非对称分裂，母细胞经过几代之后就会衰老，因此其寿命是有限的。芽殖酵母物种的延续取决于这样一个事实：它的芽每次生出时都是“年轻”的。衰老因子，如羰化蛋白和DNA环，已知仍然约束于母细胞，因而可将芽的年龄重设为零，但科学家对这种约束的机制却很不了解。现在，Shcheprova等人发现，在正在发生分裂的酵母核的核被膜中，会形成一个扩散障碍。这个障碍阻止先前存在的核孔和其他与膜相关的蛋白进入芽中。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 454, 728-734 (7 August 2008) | doi:10.1038/nature07212
A mechanism for asymmetric segregation of age during yeast budding
Zhanna Shcheprova1, Sandro Baldi1, Stephanie Buvelot Frei1, Gaston Gonnet2 & Yves Barral1
Institute of Biochemistry, Biology Department, ETH Zurich, Schafmattstrasse 18, 8093 Zurich, Switzerland
Institute of Computational Science, Department of Computer Science, ETH Zurich, Universtätstrasse 6, 8092 Zürich, Switzerland
Correspondence to: Yves Barral1 Correspondence and requests for materials should be addressed to Y.B. (Email: yves.barral@bc.biol.ethz.ch).
Abstract
Ageing and the mortality that ensues are sustainable for the species only if age is reset in newborns. In budding yeast, buds are made young whereas ageing factors, such as carbonylated proteins and DNA circles, remain confined to the ageing mother cell. The mechanisms of this confinement and their relevance are poorly understood. Here we show that a septin-dependent, lateral diffusion barrier forms in the nuclear envelope and limits the translocation of pre-existing nuclear pores into the bud. The retention of DNA circles within the mother cell depends on the presence of the diffusion barrier and on the anchorage of the circles to pores mediated by the nuclear basket. In accordance with the diffusion barrier ensuring the asymmetric segregation of nuclear age-determinants, the barrier mutant bud6 fails to properly reset age in buds. Our data involve septin-dependent diffusion barriers in the confinement of ageing factors to one daughter cell during asymmetric cell division.bioon
