Ganguly S, Skoultchi A I
J Biol Chem. 1985 Oct 5;260(22):12167-73.
We have compared the rates of alpha- and beta-globin gene transcription with the rates of mature globin mRNA appearance in the cytoplasm during the course of chemically induced differentiation of mouse erythroleukemia cells by in vivo pulse-labeling experiments. The absolute rates for both processes were determined by simultaneously measuring incorporation into globin-specific transcripts and into the cellular nucleotide pool. The latter measurements provide a determination of the absolute rate of total RNA synthesis which declines during differentiation. Transcription from the beta major and beta minor globin genes was measured separately by hybridization to cloned DNA sequences from a region of the second intron which is highly divergent in the two genes. The results show that, during dimethyl sulfoxide-stimulated differentiation, transcription of alpha and beta major globin increases 15-25-fold, whereas beta minor globin transcription is not increased. Furthermore, in both undifferentiated and differentiated cells, the absolute rates of globin transcription are about equal to the rate of appearance of mature mRNA transcripts in the cytoplasm, indicating highly efficient processing of nuclear globin transcripts to mature mRNA before and after differentiation. The results indicate that dimethyl sulfoxide-induced accumulation of globin mRNA during differentiation is controlled almost entirely at the transcriptional level.
通过体内脉冲标记实验，我们比较了在化学诱导小鼠红白血病细胞分化过程中，α-和β-珠蛋白基因转录速率与成熟珠蛋白mRNA在细胞质中出现的速率。通过同时测量掺入珠蛋白特异性转录本和细胞核苷酸池中的量，确定了这两个过程的绝对速率。后者的测量提供了对总RNA合成绝对速率的测定，该速率在分化过程中下降。通过与来自第二个内含子区域的克隆DNA序列杂交，分别测量了β-主要和β-次要珠蛋白基因的转录，该区域在两个基因中高度不同。结果表明，在二甲基亚砜刺激的分化过程中，α-和β-主要珠蛋白的转录增加了15-25倍，而β-次要珠蛋白的转录没有增加。此外，在未分化和分化的细胞中，珠蛋白转录的绝对速率大约等于成熟mRNA转录本在细胞质中出现的速率，表明在分化前后，核珠蛋白转录本高效加工成成熟mRNA。结果表明，二甲基亚砜诱导的分化过程中珠蛋白mRNA的积累几乎完全受转录水平控制。
