Suppressor mutations in Rpf2-Rrs1 or Rpl5 bypass the Cgr1 function for pre-ribosomal 5S RNP-rotation
Authors: Thoms M, Mitterer V, Kater L, Falquet L, Beckmann R, Kressler D, Hurt E
CellNetworks People: Hurt Ed
Journal: 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.