Myslinski E, Ségault V, Branlant C
Laboratoire d'Enzymologie et de Génie Génétique, Université de Nancy, France.
Science. 1990 Mar 9;247(4947):1213-6. doi: 10.1126/science.1690452.
The origin of the intervening sequences (introns), which are removed during RNA maturation, is currently unknown. They are found in most genes encoding messenger RNAs, but are lacking in almost all small nuclear (sn)RNAs. One exceptional snRNA (U6) is part of the spliceosomal machinery that is involved in messenger RNA maturation. It has been suggested that its intron arose as a result of incorrect splicing of a messenger RNA precursor. This study revealed the presence of an intron, with the characteristic features of nuclear introns from precursors to messenger RNA, in the two genes coding for Saccharomyces cerevisiae U3 snRNA. The branch point was GACTAAC instead of the TACTAAC sequence found in all yeast introns examined so far. As U3 is a nucleolar snRNA required for maturation of ribosomal RNA, its intron could not have been acquired from aberrant messenger RNA processing in a spliceosome.
在RNA成熟过程中被去除的间隔序列（内含子）的起源目前尚不清楚。它们存在于大多数编码信使RNA的基因中，但几乎在所有小核RNA（snRNA）中都不存在。一种特殊的snRNA（U6）是参与信使RNA成熟的剪接体机制的一部分。有人提出，它的内含子是信使RNA前体剪接错误的结果。这项研究揭示，在编码酿酒酵母U3 snRNA的两个基因中存在一个内含子，具有从信使RNA前体衍生而来的核内含子的特征。分支点是GACTAAC，而不是迄今为止在所有检测的酵母内含子中发现的TACTAAC序列。由于U3是核糖体RNA成熟所需的核仁snRNA，其内含子不可能从剪接体中异常的信使RNA加工过程中获得。
