Functional separation of pre-rRNA processing steps revealed by truncation of the U3 small nucleolar ribonucleoprotein component, Mpp10
Functional separation of pre-rRNA processing steps revealed by truncation of the U3 small nucleolar ribonucleoprotein component, Mpp10
复制标题
DOI：
10.1073/pnas.94.25.13536
复制
发表时间：
1997-12-09
影响因子：
11.1
通讯作者：
Baserga, SJ
中科院分区：
文献类型：
--
作者：
Lee, SJ;Baserga, SJ
U3 小核仁核糖核蛋白 (snoRNP) 是从前 rRNA 生成成熟 18S rRNA 的三个裂解事件所必需的。在酿酒酵母中，Mpp10（一种 U3 snoRNP 特异性蛋白）的描述会停止 18S rRNA 的产生并损害三个 U3 snoRNP 依赖性位点（A0、A1 和 A2）的裂解。我们已经鉴定出 Mpp10 的截短突变会影响 18S rRNA 合成并赋予冷敏感性和生长缓慢。然而，与耗尽 Mpp10 的酵母细胞不同，携带这些截短的 Mpp10 蛋白的突变体积累了一种新的前体，这是由于仅在 A0 处裂解所致。 Mpp10 截短不会改变 Mpp10 与 U3 snoRNA 的关联，也不会影响 snoRNA 或蛋白质稳定性。因此，U3 snoRNP 加工中的作用可分为 A0 位点处的切割（在存在截短的 Mpp10 时发生）和 A1/A2 位点处的切割（仅在完整的 Mpp10 存在时发生）。这些结果有力地证明了 Mpp10 在 A1/A2 位点加工中的作用。
The U3 small nucleolar ribonucleoprotein (snoRNP) is required for three cleavage events that generate the mature 18S rRNA from the pre-rRNA. In Saccharomyces cerevisiae, depiction of Mpp10, a U3 snoRNP-specific protein, halts 18S rRNA production and impairs cleavage at the three U3 snoRNP-dependent sites: A0, A1, and A2. We have identified truncation mutations of Mpp10 that affect 18S rRNA synthesis and confer cold-sensitivity and slow growth. However, distinct from yeast cells depleted of Mpp10, the mutants carrying these truncated Mpp10 proteins accumulate a novel precursor, resulting from cleavage at only A0. The Mpp10 truncations do not alter association of Mpp10 with the U3 snoRNa, nor do they affect snoRNA or protein stability. Thus, the role in processing of the U3 snoRNP can he separated into cleavage at the A0 site, which occurs in the presence of truncated Mpp10, and cleavage at the A1/A2 sites, which occurs only with intact Mpp10. These results strongly argue for a role for Mpp10 in processing at the A1/A2 sites.