Mechanisms and players of mitoribosomal biogenesis revealed in trypanosomatids

• Published in: Trends in parasitology 2022-12, Vol.38 (12), p.1053-1067
• Main Authors: Gahura, Ondřej, Chauhan, Prashant, Zíková, Alena
• Format: Article
• Language: English
• Subjects: assembly factor; biogenesis; Cryoelectron Microscopy; Mitochondria - metabolism; mitochondrial ribosomes; Mitochondrial Ribosomes - chemistry; Mitochondrial Ribosomes - metabolism; mitoribosomes; RNA, Ribosomal - analysis; RNA, Ribosomal - chemistry; RNA, Ribosomal - metabolism; Trypanosoma
• ISSN: 1471-4922; 1471-5007
• DOI: 10.1016/j.pt.2022.08.010

Translation in mitochondria is mediated by mitochondrial ribosomes, or mitoribosomes, complex ribonucleoprotein machines with dual genetic origin. Mitoribosomes in trypanosomatid parasites diverged markedly from their bacterial ancestors and other eukaryotic lineages in terms of protein composition, rRNA content, and overall architecture, yet their core functional elements remained conserved. Recent cryo-electron microscopy studies provided atomic models of trypanosomatid large and small mitoribosomal subunits and their precursors, making these parasites the organisms with the best-understood biogenesis of mitoribosomes. The structures revealed molecular mechanisms and players involved in the assembly of mitoribosomes not only in the parasites, but also in eukaryotes in general. Trypanosoma brucei and related parasites have divergent mitochondrial ribosomes with a low RNA content and an expanded proteome. Conserved functional cores of the mitoribosomes are cradled in robust protein shells.Atomic models of several precursors of large and small trypanosomal mitoribosomal subunits have been obtained by cryo-electron microscopy (cryoEM).Biogenesis of trypanosomal mitoribosomes includes a combination of conserved and lineage-specific mechanisms, and a network of numerous assembly factors.Several conserved assembly factors were visualized for the first time in the precursors of the trypanosomatid small mitoribosomal subunit (mtSSU) and large mitoribosomal subunit (mtLSU), providing mechanistic insight into their roles.