ZAKα Recognizes Stalled Ribosomes through Partially Redundant Sensor Domains

• DOI: 10.1016/j.molcel.2020.03.021
• Publication Date: 2020-04-13T14:42:00Z
• Authors: Anna Constance Vind; Goda Snieckute; Melanie Blasius; Christopher Tiedje; Nicolai Krogh; Dorte Breinholdt ...; Kasper Langebjerg...; Cathrine Nordgaard; Maxim Alexander X...; Anders Henrik Lund; Jesper Velgaard O...; Henrik Nielsen; Simon Bekker-Jensen
• Keywords: 0301 basic medicine; Protein Conformation; Sequence Homology; MAP Kinase Kinase Kinases; Enzyme Activation; 03 medical and health sciences; Protein Domains; Stress, Physiological; Peptidyl Transferases; RNA, Ribosomal, 18S; Animals; Humans; Amino Acid Sequence; Caenorhabditis elegans; Ribosomes; HeLa Cells; Signal Transduction

Impairment of ribosome function activates the MAPKKK ZAK, leading to activation of mitogen-activated protein (MAP) kinases p38 and JNK and inflammatory signaling. The mechanistic basis for activation of this ribotoxic stress response (RSR) remains completely obscure. We show that the long isoform of ZAK (ZAKα) directly associates with ribosomes by inserting its flexible C terminus into the ribosomal intersubunit space. Here, ZAKα binds helix 14 of 18S ribosomal RNA (rRNA). An adjacent domain in ZAKα also probes the ribosome, and together, these sensor domains are critically required for RSR activation after inhibition of both the E-site, the peptidyl transferase center (PTC), and ribotoxin action. Finally, we show that ablation of the RSR response leads to organismal phenotypes and decreased lifespan in the nematode Caenorhabditis elegans (C. elegans). Our findings yield mechanistic insight into how cells detect ribotoxic stress and provide experimental in vivo evidence for its physiological importance.