Dennis P P, Russell A G, Moniz De Sá M
RNA. 1997 Apr;3(4):337-43.
Hughes (1996, J Mol Biol 259:645-654) proposed that the box A region of U3 snoRNA interacts by complementary base pairing with small subunit (ss) rRNA sequences within precursor (pre-) rRNA and through rearrangement and displacement mediates the formation of the universally conserved 5' end pseudoknot. We wondered how this conserved pseudoknot might be formed in the ss rRNAs of archaeal and bacterial organisms that lack a U3 RNA. In examining the 5' external transcribed spacer (5' ETS) region in pre-rRNA transcripts from some of these organisms, we noted the presence of U3 box A-like sequences. By analogy with the U3-ss rRNA intermolecular interaction, we suggest that the box A-like 5' ETS sequence interacts through intramolecular complementary base pairing with the 5' end pseudoknot sequences within pre-rRNA; rearrangement of this structure mediates the formation of the conserved 5' end pseudoknot. If correct, this means that some of the pre-rRNA maturation-folding functions provided in trans by snoRNAs in eukaryotic organisms may be provided in cis by the spacer sequences in pre-rRNA transcripts in some bacterial or archaeal organisms lacking snoRNAs.
休斯（1996年，《分子生物学杂志》259:645 - 654）提出，U3小核仁RNA（snoRNA）的A框区域通过与前体（pre-）核糖体RNA（rRNA）内的小亚基（ss）rRNA序列进行互补碱基配对，并通过重排和置换介导普遍保守的5'端假结的形成。我们想知道在缺乏U3 RNA的古细菌和细菌生物体的ss rRNA中，这种保守的假结是如何形成的。在研究其中一些生物体的pre-rRNA转录本中的5'外部转录间隔区（5' ETS）区域时，我们注意到存在U3 A框样序列。通过与U3 - ss rRNA分子间相互作用进行类比，我们认为A框样5' ETS序列通过与pre-rRNA内的5'端假结序列进行分子内互补碱基配对相互作用；这种结构的重排介导了保守的5'端假结的形成。如果这是正确的，这意味着真核生物中由snoRNAs反式提供的一些pre-rRNA成熟折叠功能，可能在一些缺乏snoRNAs的细菌或古细菌生物体中由pre-rRNA转录本中的间隔序列顺式提供。
