Intron-dependent enzymatic formation of modified nucleosides in eukaryotic tRNAs: A review
Intron-dependent enzymatic formation of modified nucleosides in eukaryotic tRNAs: A review
复制标题
DOI：
10.1016/s0300-9084(97)83517-1
复制
发表时间：
1997-05-01
期刊：
影响因子：
3.9
通讯作者：
Simos, G
中科院分区：
文献类型：
--
作者：
Grosjean, H;SzweykowskaKulinska, Z;Simos, G
在真核细胞中，尤其是在酵母中，一些编码 tRNA 的基因含有内含子。这些在成熟过程中通过位于核膜内细胞核内的 tRNA 特异性剪接机制从前 tRNA 中去除。在内含子去除之前和之后，逐步添加一些核苷修饰，但大多数是在内含子去除之前引入。这些早期核苷修饰中的一些是由内含子依赖性酶催化的，而其他大多数是以不依赖于内含子的方式催化的。在本文中，我们回顾了所有已知的情况，其中核苷修饰被证明严格依赖于内含子的存在。这些是几种真核tRNA 反密码子位置34、35 和36 处的假尿苷以及位置34 处的5-甲基胞嘧啶。相应的内含子依赖性修饰酶的一个共同特性是它们的活性基本上依赖于前tRNA分子的局部特定结构，该前tRNA分子包含由内含子结构域延长的反密码子茎和环。因此，内含子显然可以作为内部（顺式）RNA，通过在 tRNA 中为选定的核修饰酶提供瞬时靶位点来指导核苷修饰。这种情况可能类似于最近发现的（反式）snoRNA引导的真核细胞核仁内核糖体RNA的核糖甲基化过程。
In eukaryotic cells, especially in yeast, several genes encoding tRNAs contain introns. These are removed from pre-tRNAs during the maturation process by a tRNA-specific splicing machinery that is located within the nucleus at the nuclear envelope. Before and after the intron removal, several nucleoside modifications are added in a stepwise manner, but most of them are introduced prior to intron removal. Some of these early nucleoside modifications are catalyzed by intron-dependent enzymes while most of the others are catalyzed in an intron-independent manner. In the present paper, we review all known cases where the nucleoside modifications were shown to depend strictly on the presence of an intron. These are pseudouridines at anticodon positions 34, 35 and 36 and 5-methylcytosine at position 34 of several eukaryotic tRNAs. One common property of the corresponding intron-dependent modifying enzymes is that their activities are essentially dependent on the local specific architecture of the pre-tRNA molecule that comprises the anticodon stem and loop prolonged by the intron domain. Thus introns clearly serve as internal (cis-type) RNAs that guide nucleoside modifications by providing transient target sites in tRNA for selected nuclear modifying enzymes. This situation may be similar to the recently discovered (trans-type) snoRNA-guided process of ribose methylations of ribosomal RNAs within the nucleolus of eukaryotic cells.