Kennedy B K, Austriaco N R, Guarente L
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
J Cell Biol. 1994 Dec;127(6 Pt 2):1985-93. doi: 10.1083/jcb.127.6.1985.
The yeast Saccharomyces cerevisiae typically divides asymmetrically to give a large mother cell and a smaller daughter cell. As mother cells become old, they enlarge and produce daughter cells that are larger than daughters derived from young mother cells. We found that occasional daughter cells were indistinguishable in size from their mothers, giving rise to a symmetric division. The frequency of symmetric divisions became greater as mother cells aged and reached a maximum occurrence of 30% in mothers undergoing their last cell division. Symmetric divisions occurred similarly in rad9 and ste12 mutants. Strikingly, daughters from old mothers, whether they arose from symmetric divisions or not, displayed reduced life spans relative to daughters from young mothers. Because daughters from old mothers were larger than daughters from young mothers, we investigated whether an increased size per se shortened life span and found that it did not. These findings are consistent with a model for aging that invokes a senescence substance which accumulates in old mother cells and is inherited by their daughters.
酿酒酵母通常进行不对称分裂，产生一个较大的母细胞和一个较小的子细胞。随着母细胞变老，它们会增大，并产生比来自年轻母细胞的子细胞更大的子细胞。我们发现，偶尔会有子细胞在大小上与它们的母细胞无法区分，从而产生对称分裂。随着母细胞变老，对称分裂的频率增加，在进行最后一次细胞分裂的母细胞中，对称分裂的发生率最高可达30%。在rad9和ste12突变体中，对称分裂的情况类似。令人惊讶的是，无论是否来自对称分裂，来自老龄母细胞的子细胞相对于来自年轻母细胞的子细胞，其寿命都缩短了。由于来自老龄母细胞的子细胞比来自年轻母细胞的子细胞更大，我们研究了细胞大小本身的增加是否会缩短寿命，结果发现并非如此。这些发现与一种衰老模型一致，该模型认为存在一种衰老物质，它在老龄母细胞中积累，并由它们的子细胞继承。
