Rps26 directs mRNA-specific translation by recognition of Kozak sequence elements

The “Kozak sequence”, immediately upstream of the start codon, regulates the translational efficiency of an mRNA. Nevertheless, how this sequence is recognized remains unexplored. Here, we describe a novel approach to separate two ribosome populations from the same cells and use this method, and RNA-seq, to identify the mRNAs bound to ribosomes with and without Rps26, a protein linked to the pathogenesis of Diamond Blackfan Anemia (DBA). These analyses reveal that Rps26 contributes to recognition of the Kozak sequence in well-translated mRNAs, and that Rps26-deficient ribosomes preferentially translate mRNA from select stress response pathways. Surprisingly, we demonstrate that exposure of cells to these stresses leads to the formation of Rps26-deficient ribosomes and to the translation of their targets. Thus, Rps26-deficient ribosomes play aberrant pathogenic roles in DBA as well as physiological roles in augmenting the well-characterized stress transcriptional response with a heretofore unknown translational stress response, thereby creating a feed forward loop in gene-expression. Overall design: Comparison of the mRNA bound to two classes of ribosomes in three biological replicates.

7

Ferretti MB, Ghalei H, Ward EA, Potts EL, Karbstein K