Hereford L M, Osley M A, Ludwig T R, McLaughlin C S
Cell. 1981 May;24(2):367-75. doi: 10.1016/0092-8674(81)90326-3.
The levels of H2A and H2B mRNAs as a function of cell-cycle stage were determined by hybridization methods. The analysis was extended to H3 and H4 mRNAs by in vitro translation. Cells were partitioned into cell-cycle stages either by centrifugal elutriation or by G1 synchronization with the yeast mating pheromone, alpha factor. The data lead to the following conclusions. First, histone mRNA can be detected in significant quantities only in S-phase cells. Second, the point of maximal accumulation of histone mRNA is not coincident with the point of maximal DNA synthesis; rather, histone mRNA begins accumulating very early in S, reaching a maximum when less than one half of the DNA has replicated. From this point in the cell cycle the histone mRNA levels decrease, reaching basal levels at the end of S. Third, in spite of the fact that the rate of histone mRNA accumulation is not coincident with the rate of DNA synthesis, the two processes are coupled; inhibition of DNA synthesis results in an extremely rapid disappearance of histone mRNA that is much shorter than the normal histone mRNA half-life. Fourth, there is no visible accumulation of mRNA precursors at any cell-cycle stage. We can conclude that, in yeast, histone mRNA levels are tightly and coordinately regulated throughout cell division and that this regulation most likely occurs at both transcriptional and posttranscriptional levels. We also show that the two genetically unlinked H2B genes present in yeast are both expressed at comparable levels and are regulated. The regulation is probably sequence-specific, since genes in close proximity to the histones are not subject to cell-cycle control.
通过杂交方法确定了作为细胞周期阶段函数的H2A和H2B mRNA水平。通过体外翻译将分析扩展到H3和H4 mRNA。细胞通过离心淘析或用酵母交配信息素α因子进行G1同步化被划分为细胞周期阶段。数据得出以下结论。首先，仅在S期细胞中可大量检测到组蛋白mRNA。其次，组蛋白mRNA的最大积累点与最大DNA合成点不一致；相反，组蛋白mRNA在S期很早就开始积累，当不到一半的DNA复制时达到最大值。从细胞周期的这一点开始，组蛋白mRNA水平下降，在S期末达到基础水平。第三，尽管组蛋白mRNA积累速率与DNA合成速率不一致，但这两个过程是偶联的；DNA合成的抑制导致组蛋白mRNA极其迅速地消失，其消失速度比正常组蛋白mRNA半衰期短得多。第四，在任何细胞周期阶段都没有可见的mRNA前体积累。我们可以得出结论，在酵母中，组蛋白mRNA水平在整个细胞分裂过程中受到紧密且协调的调节，并且这种调节很可能发生在转录和转录后水平。我们还表明，酵母中存在的两个遗传上不连锁的H2B基因均以相当的水平表达并受到调节。这种调节可能是序列特异性的，因为与组蛋白紧密相邻的基因不受细胞周期控制。
