Yeast ribosomal protein L7 and its homologue Rlp7 are simultaneously present at distinct sites on pre-60S ribosomal particles.
Yeast ribosomal protein L7 and its homologue Rlp7 are simultaneously present at distinct sites on pre-60S ribosomal particles.
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DOI：
10.1093/nar/gkt726
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发表时间：
2013-11
影响因子：
14.9
通讯作者：
de la Cruz J
中科院分区：
文献类型：
--
作者：
Babiano R;Badis G;Saveanu C;Namane A;Doyen A;Díaz-Quintana A;Jacquier A;Fromont-Racine M;de la Cruz J
核糖体的生物发生需要酿酒酵母中的300个组装因子。核糖体组装因子Imp3、Mrt4、Rlp7和Rlp24与核糖体蛋白S9、P0、L7和L24具有序列相似性，提示这些核糖体前因子可能是阻止相应核糖体蛋白过早组装到新生核糖体的占位符。然而，我们发现L7是Rlp7相关复合体的一个高度特异的成分，表明这两种蛋白质可以同时与核糖体前颗粒结合。交联和cDNA分析实验表明，Rlp7与27S前rRNA的ITS2区域结合，在螺旋III和与前rRNA加工位点C1和E相邻的区域，而L7与成熟的25S和5S rRNA结合，并主要与25S rRNA内的螺旋ES7Lb交联。因此，尽管我们预测了Rlp7和L7的结构相似，但我们的数据表明，Rlp7和L7明显结合在同一个1960年代前粒子上的不同位置。我们的结果还表明，在60S核糖体亚基成熟过程中，Rlp7促进了ITS2发夹结构的形成。
Ribosome biogenesis requires >300 assembly factors in Saccharomyces cerevisiae. Ribosome assembly factors Imp3, Mrt4, Rlp7 and Rlp24 have sequence similarity to ribosomal proteins S9, P0, L7 and L24, suggesting that these pre-ribosomal factors could be placeholders that prevent premature assembly of the corresponding ribosomal proteins to nascent ribosomes. However, we found L7 to be a highly specific component of Rlp7-associated complexes, revealing that the two proteins can bind simultaneously to pre-ribosomal particles. Cross-linking and cDNA analysis experiments showed that Rlp7 binds to the ITS2 region of 27S pre-rRNAs, at two sites, in helix III and in a region adjacent to the pre-rRNA processing sites C1 and E. However, L7 binds to mature 25S and 5S rRNAs and cross-linked predominantly to helix ES7Lb within 25S rRNA. Thus, despite their predicted structural similarity, our data show that Rlp7 and L7 clearly bind at different positions on the same pre-60S particles. Our results also suggest that Rlp7 facilitates the formation of the hairpin structure of ITS2 during 60S ribosomal subunit maturation.
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