RT Journal Article
SR Electronic
T1 Visualising formation of the ribosomal active site in mitochondria
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.03.19.436169
DO 10.1101/2021.03.19.436169
A1 Viswanathan Chandrasekaran
A1 Nirupa Desai
A1 Nicholas O. Burton
A1 Hanting Yang
A1 Jon Price
A1 Eric A. Miska
A1 V. Ramakrishnan
YR 2021
UL http://biorxiv.org/content/early/2021/03/20/2021.03.19.436169.abstract
AB Ribosome assembly is an essential and complex process that is regulated at each step by specific biogenesis factors. Using cryo-electron microscopy, we identify and order major steps in the formation of the highly conserved peptidyl transferase centre (PTC) and tRNA binding sites in the large subunit of the human mitochondrial ribosome (mitoribosome). The conserved GTPase GTPBP7 regulates the folding and incorporation of core 16S ribosomal RNA (rRNA) helices and the ribosomal protein bL36m, and ensures that the PTC base U3039 has been 2′-O-methylated. Additionally, GTPBP7 binds the RNA methyltransferase NSUN4 and MTERF4, which facilitate earlier steps by sequestering H68-71 of the 16S rRNA and allowing biogenesis factors to access the maturing PTC. Consistent with the central role of NSUN4•MTERF4 and GTPBP7 during mitoribosome biogenesis, in vivo mutagenesis designed to disrupt binding of their Caenorhabditis elegans orthologs to the large subunit potently activates mitochondrial stress responses and results in severely reduced viability, developmental delays and sterility. Next-generation RNA sequencing reveals widespread gene expression changes in these mutant animals that are indicative of mitochondrial stress response activation. We also answer the long-standing question of why NSUN4 but not its enzymatic activity, is indispensable for mitochondrial protein synthesis in metazoans.Competing Interest StatementThe authors have declared no competing interest.