Niwa M, Berget S M
Marrs McClean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030.
Gene Expr. 1991 Apr;1(1):5-14.
Vertebrate premessenger RNAs are usually spliced and polyadenylated. In vivo analysis of the relative kinetics of the two reactions is difficult. We have used in vitro processing systems to investigate the order of splicing and polyadenylation of chimeric precursor RNAs containing a single intron and a poly(A) site. Polyadenylated, but not spliced, intermediate RNA appeared first and reached a low steady-state level early during incubation, properties consistent with its being a reaction intermediate in the production of doubly-processed spliced and polyadenylated product RNA. The kinetics of polyadenylation suggested that polyadenylated RNA was the only intermediate in the production of doubly-processed RNA. Spliced, but not polyadenylated, RNA also appeared. This species, however, continued to accumulate during reaction, and could not be chased into product spliced and polyadenylated RNA. These data support a preferred order of reaction for 3' terminal introns and exons in which polyadenylation precedes splicing.
脊椎动物的前体信使RNA通常会进行剪接和聚腺苷酸化。对这两个反应的相对动力学进行体内分析很困难。我们使用体外加工系统来研究含有单个内含子和聚腺苷酸化位点的嵌合前体RNA的剪接和聚腺苷酸化顺序。首先出现的是聚腺苷酸化但未剪接的中间RNA，并且在孵育早期达到较低的稳态水平，这些特性与其作为双加工剪接和聚腺苷酸化产物RNA产生过程中的反应中间体一致。聚腺苷酸化的动力学表明，聚腺苷酸化RNA是双加工RNA产生过程中的唯一中间体。剪接但未聚腺苷酸化的RNA也出现了。然而，这个物种在反应过程中持续积累，并且无法转化为剪接和聚腺苷酸化的产物RNA。这些数据支持了3'末端内含子和外显子的优先反应顺序，即聚腺苷酸化先于剪接。
