Rickles R, Marashi F, Sierra F, Clark S, Wells J, Stein J, Stein G
Proc Natl Acad Sci U S A. 1982 Feb;79(3):749-53. doi: 10.1073/pnas.79.3.749.
Although it is generally agreed that histone protein synthesis is restricted to the S phase of the cell cycle--and therefore parallels DNA replication--both transcriptional and posttranscriptional levels of control have been invoked. Using blot hybridization with several cloned genomic human histone sequences representing different histone gene clusters as probes, we have assessed the steady-state level of histone RNAs in the nucleus and cytoplasm of G1 and S phase HeLa S3 cells. The representation of histone mRNA sequences of G1 compared with S phase cells was less than 1% in the cytoplasm and approximately 1% in the nucleus. These data are consistent with transcriptional control, but we cannot completely dismiss the possibility that regulation of histone gene expression is, to some extent, mediated posttranscriptionally. If histone gene transcription does occur in G1, the RNAs must either be rapidly degraded or be transcribed to a limited extent compared with S phase. An unexpected result was obtained when a blot of cytoplasmic RNA from G1 and S phase cells was hybridized with lambda HHG 41 DNA (containing H3 and H4 human genomic histone sequences). Although hybridization with histone mRNAs was observed for RNAs from S phase but not from G1 cells, hybridization with a nonhistone RNA of approximately 330 nucleotides present predominantly in G1 was also observed.
虽然人们普遍认为组蛋白的合成仅限于细胞周期的S期，因此与DNA复制同步，但转录水平和转录后水平的调控都被提及。我们使用代表不同组蛋白基因簇的几个克隆的基因组人类组蛋白序列作为探针进行印迹杂交，评估了G1期和S期HeLa S3细胞核和细胞质中组蛋白RNA的稳态水平。与S期细胞相比，G1期细胞的组蛋白mRNA序列在细胞质中的占比不到1%，在细胞核中约为1%。这些数据与转录调控一致，但我们不能完全排除组蛋白基因表达调控在某种程度上是由转录后介导的可能性。如果组蛋白基因转录确实在G1期发生，那么与S期相比，这些RNA要么被迅速降解，要么转录程度有限。当用λHHG 41 DNA（包含H3和H4人类基因组组蛋白序列）与G1期和S期细胞的细胞质RNA印迹杂交时，得到了一个意外的结果。虽然在S期细胞的RNA中观察到与组蛋白mRNA的杂交，但在G1期细胞中未观察到，但同时也观察到与一种主要存在于G1期的约330个核苷酸的非组蛋白RNA的杂交。
