Biochemistry Centre, University of Heidelberg, Heidelberg, 69120, Germany.
Gene Center, University of Munich, Munich, 81377, Germany.
Nat Commun. 2018 Oct 5;9(1):4094. doi: 10.1038/s41467-018-06660-w.
During eukaryotic 60S biogenesis, the 5S RNP requires a large rotational movement to achieve its mature position. Cryo-EM of the Rix1-Rea1 pre-60S particle has revealed the post-rotation stage, in which a gently undulating α-helix corresponding to Cgr1 becomes wedged between Rsa4 and the relocated 5S RNP, but the purpose of this insertion was unknown. Here, we show that cgr1 deletion in yeast causes a slow-growth phenotype and reversion of the pre-60S particle to the pre-rotation stage. However, spontaneous extragenic suppressors could be isolated, which restore growth and pre-60S biogenesis in the absence of Cgr1. Whole-genome sequencing reveals that the suppressor mutations map in the Rpf2-Rrs1 module and Rpl5, which together stabilize the unrotated stage of the 5S RNP. Thus, mutations in factors stabilizing the pre-rotation stage facilitate 5S RNP relocation upon deletion of Cgr1, but Cgr1 itself could stabilize the post-rotation stage.
在真核生物 60S 生物发生过程中，5S RNP 需要进行大量的旋转运动才能达到成熟位置。Rix1-Rea1 前 60S 颗粒的冷冻电镜显示了旋转后的阶段，其中对应于 Cgr1 的柔和起伏的α-螺旋被楔入 Rsa4 和重新定位的 5S RNP 之间，但这种插入的目的尚不清楚。在这里，我们表明酵母中 cgr1 的缺失会导致生长缓慢的表型，并使前 60S 颗粒返回到前旋转阶段。然而，可以分离出自发的异位抑制子，这些抑制子在没有 Cgr1 的情况下恢复生长和前 60S 生物发生。全基因组测序表明，抑制子突变位于 Rpf2-Rrs1 模块和 Rpl5 中，它们共同稳定 5S RNP 的未旋转阶段。因此，稳定前旋转阶段的因素突变会促进 Cgr1 缺失时 5S RNP 的重新定位，但 Cgr1 本身可以稳定后旋转阶段。
