Marine Biological Laboratory, Woods Hole, MA, United States of America.
Dept. of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH, United States of America.
PLoS One. 2018 Dec 21;13(12):e0209301. doi: 10.1371/journal.pone.0209301. eCollection 2018.
Cell populations across nearly all forms of life generally maintain a characteristic cell type-dependent size, but how size control is achieved has been a long-standing question. The G1/S boundary of the cell cycle serves as a major point of size control, and mechanisms operating here restrict passage of cells to Start if they are too small. In contrast, it is less clear how size is regulated post-Start, during S/G2/M. To gain further insight into post-Start size control, we prepared budding yeast that can be reversibly blocked from bud initiation. While blocked, cells continue to grow isotropically, increasing their volume by more than an order of magnitude over unperturbed cells. Upon release from their block, giant mothers reenter the cell cycle and their progeny rapidly return to the original unperturbed size. We found this behavior to be consistent with a size-invariant 'timer' specifying the duration of S/G2/M. These results indicate that yeast use at least two distinct mechanisms at different cell cycle phases to ensure size homeostasis.
几乎所有形式的生命中的细胞群体通常都保持着特征性的细胞类型依赖性大小，但大小控制是如何实现的一直是一个长期存在的问题。细胞周期的 G1/S 边界是大小控制的主要控制点，这里的机制如果细胞太小就会限制它们进入起始点。相比之下，在 S/G2/M 期间，大小是如何被调节的就不太清楚了。为了更深入地了解起始后的大小控制，我们制备了可以可逆地阻止芽起始的出芽酵母。在被阻断期间，细胞继续各向同性生长，其体积比未受干扰的细胞增加了一个数量级以上。从阻断中释放出来后，巨大的母细胞重新进入细胞周期，它们的后代迅速恢复到原来的未受干扰的大小。我们发现这种行为与指定 S/G2/M 持续时间的大小不变的“定时器”一致。这些结果表明，酵母在不同的细胞周期阶段使用至少两种不同的机制来确保大小的恒定性。
