Harpold M M, Evans R M, Salditt-Georgieff M, Darnell J E
Cell. 1979 Aug;17(4):1025-35. doi: 10.1016/0092-8674(79)90341-6.
We constructed cloned DNA sequences complementary to unselected mRNAs [poly(A)+ cytoplasmic RNA] from Chinese hamster ovary cells and used them in RNA:DNA hybridization experiments. Each cloned DNA hybridized a single mRNA from 1.3-3.5 kb in length. The relative rates of labeling (transcription rates) of nuclear RNA complementary to each individual DNA segment varied approximately 10 fold. The relative cytoplasmic concentration of the same specific RNA sequences in the mRNA after an equilibrium labeling of the cells varied approximately 100 fold. In addition, we estimated the sizes of the nuclear RNA precursor molecules to these cytoplasmic mRNAs. Four main conclusions arise from these studies. First, the primary RNA transcripts, which range in size from 2.4-13.5 kb, are 2-6 times larger than the mRNAs; second, each cloned DNA segment is complementary to only one species of mRNA; third, for the RNA complementary to at least three of the nine cloned DNA segments, the relative cytoplasmic content is considerably different from the relative rate of nuclear RNA synthesis, suggesting the post-transcriptional events are involved in the determination of the cytoplasmic concentrations of some mammalian mRNAs; and fourth, the fraction of total nonribosomal nuclear RNA complementary to the nine cloned DNA segments is in most cases 10 fold less than the fraction of cytoplasmic mRNA complementary to the same cloned DNA segments, suggesting the synthesis of many hnRNA molecules that are qualitatively different from those which eventually contribute mRNA to the cytoplasm.
我们构建了与中国仓鼠卵巢细胞中未筛选的mRNA（聚腺苷酸加尾的细胞质RNA）互补的克隆DNA序列，并将其用于RNA:DNA杂交实验。每个克隆的DNA与一条长度为1.3 - 3.5 kb的单一mRNA杂交。与每个单独DNA片段互补的核RNA的相对标记速率（转录速率）大约相差10倍。细胞进行平衡标记后，mRNA中相同特定RNA序列的相对细胞质浓度大约相差100倍。此外，我们估算了这些细胞质mRNA的核RNA前体分子的大小。这些研究得出了四个主要结论。第一，大小在2.4 - 13.5 kb范围内的初级RNA转录本比mRNA大2 - 6倍；第二，每个克隆的DNA片段仅与一种mRNA互补；第三，对于与九个克隆DNA片段中至少三个互补的RNA，其相对细胞质含量与核RNA合成的相对速率有很大差异，这表明转录后事件参与了某些哺乳动物mRNA细胞质浓度的决定；第四，与九个克隆DNA片段互补的非核糖体核RNA总量的比例在大多数情况下比与相同克隆DNA片段互补的细胞质mRNA的比例少10倍，这表明许多核不均一RNA分子在性质上与最终为细胞质提供mRNA的分子不同。
