Maquat L E, Kinniburgh A J, Beach L R, Honig G R, Lazerson J, Ershler W B, Ross J
Proc Natl Acad Sci U S A. 1980 Jul;77(7):4287-91. doi: 10.1073/pnas.77.7.4287.
Nucleated bone marrow cells from normal individuals and from three patients with homozygous beta+-thalassemia were pulse-labeled with tritiated nucleosides. The processing of the newly synthesized globin mRNA precursors was monitored by inhibiting additional transcription with actinomycin D for 30 min. Human beta-globin mRNA is derived from its precursor via a series of reactions that generate processing intermediates. In nonthalassemic cells the precursor is processed efficiently to mature mRNA during the chase. In contrast, in beta+-thalassemic cells the processing of beta-globin RNA is defective. In one patient the beta-globin mRNA precursor turns over during the chase, but some of the intermediate RNAs accumulate and are not processed to mRNA. In two other patients a large fraction of the precursor and intermediate RNAs is not processed to mRNA. The alpha-globin mRNA precursor and intermediates are processed efficiently to mRNA-sized molecules in thalassemic and normal cells. The reduction in the rate of beta-globin but not alpha-globin RNA processing accounts for the alpha/beta globin mRNA imbalance in thalassemic erythroid cells. We discuss the possibility that the genetic lesions in beta+-thalassemia are at splicing signal sites within intervening sequences of the beta-globin gene.
用氚标记的核苷对来自正常个体以及三名纯合β⁺地中海贫血患者的有核骨髓细胞进行脉冲标记。通过用放线菌素D抑制额外转录30分钟来监测新合成的珠蛋白mRNA前体的加工过程。人β珠蛋白mRNA通过一系列产生加工中间体的反应从其前体衍生而来。在非地中海贫血细胞中，前体在追踪过程中被有效地加工成成熟的mRNA。相比之下，在β⁺地中海贫血细胞中，β珠蛋白RNA的加工存在缺陷。在一名患者中，β珠蛋白mRNA前体在追踪过程中周转，但一些中间RNA积累且未被加工成mRNA。在另外两名患者中，大部分前体和中间RNA未被加工成mRNA。α珠蛋白mRNA前体和中间体在贫血和正常细胞中被有效地加工成mRNA大小的分子。β珠蛋白而非α珠蛋白RNA加工速率的降低导致了地中海贫血红细胞中α/β珠蛋白mRNA的失衡。我们讨论了β⁺地中海贫血中的遗传损伤可能位于β珠蛋白基因间隔序列内的剪接信号位点的可能性。
