Enright C A, Maxwell E S, Eliceiri G L, Sollner-Webb B
Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
RNA. 1996 Nov;2(11):1094-9.
The nucleolus, the compartment in which the large ribosomal RNA precursor (pre-rRNA) is synthesized, processed through a series of nucleolytic cleavages and modifications into the mature 18S, 5.8S, and 28S rRNAs, and assembled with proteins to form ribosomal subunits, also contains many small nucleolar RNAs (snoRNAs). We present evidence that the first processing event in mouse rRNA maturation, cleavage within the 5' external transcribed spacer, is facilitated by at least four snoRNAs: U14, U17(E1), and E3, as well as U3. These snoRNAs do not augment this processing by directing 2'-O-methylation of the pre-rRNA. A macromolecular complex in which this 5'ETS processing occurs may then function in the processing of 18S rRNA.
核仁是合成大核糖体RNA前体（前体rRNA）的区域，前体rRNA通过一系列核酸裂解和修饰加工成成熟的18S、5.8S和28S rRNA，并与蛋白质组装形成核糖体亚基，其中还包含许多小核仁RNA（snoRNA）。我们提供的证据表明，小鼠rRNA成熟过程中的第一个加工事件，即5'外部转录间隔区内的裂解，至少由四种snoRNA促进：U14、U17（E1）和E3以及U3。这些snoRNA不会通过指导前体rRNA的2'-O-甲基化来增强这种加工。然后，发生这种5'ETS加工的大分子复合物可能在18S rRNA的加工中起作用。
