Scaling of transcript abundance with cell size and the commitment to cell division

摘要： 在提交给单元之前，所有单元必须增长到最小大小--“临界大小” 组织。这种大小要求可以防止单元格变得太大或太小，而且它还 根据营养的可获得性和细胞的大量生长来协调分裂。作为一个结果 大小控制时，细胞具有窄的细胞大小的特征分布。尽管几十年来 研究表明，目前尚不清楚细胞是如何测量和响应大小的，也不知道为什么机械地最小 规模是承诺划分的必要条件。我们最近发现，作为G1期 酵母细胞在大小上生长，数百个mRNAs在系统中以更高的 更高的水平--它们的增长速度快于规模的增长和集中度的增长。 其他的mRNA则相反--它们的增长速度慢于大小的增长，因此减少了 全神贯注。引人注目的是，激活细胞周期的基因属于第一组，而 抑制细胞周期的基因属于第二类。这表明这一比例 激活剂和抑制剂随着G1期细胞的生长而增加，这是实现这一目标的关键 触发细胞周期进入的许多激活剂和抑制剂的比率。在这里，我们测试一下 这个想法，通过检查酵母S.pombe和人类细胞中随大小变化的信使核糖核酸， 我们将检验两个理论，以解释随尺寸变化的差异比例机制。最后，我们将询问是否 类似的缩放也发生在翻译级别上。

Abstract: All cells must grow to a minimum size—the “critical size”—before they can commit to cell division. This size requirement prevents cells from becoming too big or too small, and it co- ordinates division with the availability of nutrients and cell growth in mass. As a consequence of size control, cells have narrow and characteristic distributions of cell size. Despite decades of study, it is unknown how cells measure and respond to size, or why mechanistically a minimum size is required for commitment to division. We have recently discovered that as G1 phase yeast cells grow in size, several hundred mRNAs are systematically expressed at higher and higher levels—they increase faster than the increase in size, and increase in concentration. Other mRNAs do the opposite—they increase slower than the increase in size, and so decrease in concentration. Strikingly, genes that activate the cell cycle fall into the first group, while genes that inhibit the cell cycle fall into the second group. This suggests that the ratio of activators to inhibitors increases as G1 phase cells grow, and that it is achievement of a critical ratio of many activators to inhibitors that triggers cell cycle entry. Here, we test the generality of this idea, by examining mRNA scaling-with-size in the yeast S. pombe and in human cells, and we will test two theories for the mechanism of differential-scaling-with-size. Finally we will ask if similar scaling occurs at the level of translation.