Alterman R B, Ganguly S, Schulze D H, Marzluff W F, Schildkraut C L, Skoultchi A I
Mol Cell Biol. 1984 Jan;4(1):123-32. doi: 10.1128/mcb.4.1.123-132.1984.
The mechanisms responsible for the periodic accumulation and decay of histone mRNA in the mammalian cell cycle were investigated in mouse erythroleukemia cells, using a cloned mouse H3 histone gene probe that hybridizes with most or all H3 transcripts. Exponentially growing cells were fractionated into cell cycle-specific stages by centrifugal elutriation, a method for purifying cells at each stage of the cycle without the use of treatments that arrest growth. Measurements of H3 histone mRNA content throughout the cell cycle show that the mRNA accumulates gradually during S phase, achieving its highest value in mid-S phase when DNA synthesis is maximal. The mRNA content then decreases as cells approach G2. These results demonstrate that the periodic synthesis of histones during S phase is due to changes in the steady-state level of histone mRNA. They are consistent with the conventional view in which histone synthesis is regulated coordinately with DNA synthesis in the cell cycle. The periodic accumulation and decay of H3 histone mRNA appear to be controlled primarily by changes in the rate of appearance of newly synthesized mRNA in the cytoplasm, determined by pulse-labeling whole cells with [3H]uridine. Measurements of H3 mRNA turnover by pulse-chase experiments with cells in S and G2 did not provide evidence for changes in the cytoplasmic stability of the mRNA during the period of its decay in late S and G2. Furthermore, transcription measurements carried out by brief pulse-labeling in vivo and by in vitro transcription in isolated nuclei indicate that the rate of H3 gene transcription changes to a much smaller extent than the steady-state levels of the mRNA or the appearance of newly synthesized mRNA in the cytoplasm. The results suggest that post-transcriptional processes make an important contribution to the periodic accumulation and decay of histone mRNA and that these processes may operate within the nucleus.
利用与大多数或所有H3转录本杂交的克隆小鼠H3组蛋白基因探针，在小鼠红白血病细胞中研究了哺乳动物细胞周期中组蛋白mRNA周期性积累和衰减的机制。通过离心淘析将指数生长的细胞分离为细胞周期特异性阶段，离心淘析是一种在不使用阻止生长的处理方法的情况下，纯化细胞周期各阶段细胞的方法。对整个细胞周期中H3组蛋白mRNA含量的测量表明，mRNA在S期逐渐积累，在DNA合成最大的S期中期达到最高值。然后，随着细胞接近G2期，mRNA含量下降。这些结果表明，S期组蛋白的周期性合成是由于组蛋白mRNA稳态水平的变化。它们与传统观点一致，即组蛋白合成在细胞周期中与DNA合成协调调节。H3组蛋白mRNA的周期性积累和衰减似乎主要受细胞质中新合成mRNA出现速率变化的控制，这是通过用[3H]尿苷脉冲标记全细胞来确定的。用处于S期和G2期的细胞进行脉冲追踪实验对H3 mRNA周转的测量，没有提供证据表明在S期末期和G2期mRNA衰减期间其细胞质稳定性发生变化。此外，通过体内短暂脉冲标记和分离细胞核中的体外转录进行的转录测量表明，H3基因转录速率的变化程度远小于mRNA的稳态水平或细胞质中新合成mRNA的出现。结果表明，转录后过程对组蛋白mRNA的周期性积累和衰减起重要作用，并且这些过程可能在细胞核内发生。
