Nilsen T W, Maroney P A, Robertson H D, Baglioni C
Mol Cell Biol. 1982 Feb;2(2):154-60. doi: 10.1128/mcb.2.2.154-160.1982.
Heterogeneous nuclear RNA contains double-stranded regions that are not found in mRNA and that may serve as recognition elements for processing enzymes. The double-stranded regions of heterogeneous nuclear RNA prepared from HeLa cells promoted the synthesis of (2',5')oligoadenylate [(2',5')oligo(A) or (2'5')An] when incubated with (2',5')An polymerase. This enzyme is present in elevated levels in interferon-treated cells, and labeled heterogeneous nuclear RNA incubated with extracts of these cells is preferentially cleaved, since mRNA included in the same incubations is not appreciably degraded. The cleavage of heterogenous nuclear RNA is caused by the synthesis of (2'5')An and by a "localized" activation of the (2',5')An-dependent endonuclease, since it was enhanced by ATP, the substrate of the (2',5')An polymerase, and inhibited by 2'-dATP and ethidium bromide. Both of these compounds suppress the synthesis of (2',5')An, the first by competitive inhibition and the latter by intercalating into double-stranded RNA. The possible role of double-stranded regions and of the (2',5')An polymerase-endonuclease system in the processing of heterogeneous nuclear RNA is discussed.
不均一核RNA含有在mRNA中未发现的双链区域，这些区域可能作为加工酶的识别元件。用从HeLa细胞制备的不均一核RNA的双链区域与(2',5')寡腺苷酸[(2',5')oligo(A)或(2'5')An]聚合酶一起温育时，能促进(2',5')寡腺苷酸的合成。这种酶在经干扰素处理的细胞中水平升高，用这些细胞的提取物与标记的不均一核RNA一起温育时，不均一核RNA会被优先切割，因为在相同温育体系中的mRNA没有明显降解。不均一核RNA的切割是由(2'5')An的合成以及(2',5')An依赖性核酸内切酶的“局部”激活引起的，因为它会被(2',5')An聚合酶的底物ATP增强，并被2'-dATP和溴化乙锭抑制。这两种化合物都抑制(2',5')An的合成，前者通过竞争性抑制，后者通过插入双链RNA来实现。本文讨论了双链区域以及(2',5')An聚合酶-核酸内切酶系统在不均一核RNA加工中的可能作用。
