Human GTPBP10 is required for mitoribosome maturation

Abstract

Most steps on the biogenesis of the mitochondrial ribosome (mitoribosome) occur near the mitochondrial DNA nucleoid, in RNA granules, which contain dedicated RNA metabolism and mitoribosome assembly factors. Here, analysis of the RNA granule proteome identified the presence of a set of small GTPases that belong to conserved families of ribosome assembly factors. We show that GTPBP10, a member of the conserved Obg family of P-loop small G proteins, is a mitochondrial protein and have used gene-editing technologies to create a HEK293T cell line KO for GTPBP10. The absence of GTPBP10 leads to attenuated mtLSU and mtSSU levels and the virtual absence of the 55S monosome, which entirely prevents mitochondrial protein synthesis. We show that a fraction of GTPBP10 cosediments with the large mitoribosome subunit and the monosome. GTPBP10 physically interacts with the 16S rRNA, but not with the 12S rRNA, and crosslinks with several mtLSU proteins. Additionally, GTPBP10 is indirectly required for efficient processing of the 12S-16S rRNA precursor transcript, which could explain the mtSSU accumulation defect. We propose that GTPBP10 primarily ensures proper mtLSU maturation and ultimately serves to coordinate mtSSU and mtLSU accumulation then providing a quality control check-point function during mtLSU assembly that minimizes premature subunit joining.

RCC1L (WBSCR16) isoforms coordinate mitochondrial ribosome assembly through their interaction with GTPases

“…In human mitochondria, five GTPases involved in ribosome biogenesis have been described to date: MTG1 (GTPBP7) couples mtLSU assembly with bridge formation between mtLSU and mtSSU [ 9 ] [ 10 ], MTG2 (GTPBP5) interacts with the immature mt-LSU [ 10 ], GTPBP10 is required for mtLSU late assembly [ 11 , 12 ], ERAL1 stabilises 12S rRNA prior to the final maturation of the mtSSU [ 13 ] and C4orf14 binds MRPs of the mtSSU facilitating its assembly [ 14 ]. Two additional GTPases, GTPBP6 and GTPBP8, have recently been found in DDX28 pulldowns but they are still uncharacterized [ 12 ]. In addition, mitoribosomes have acquired an intrinsic GTPase activity thanks to the structural component of the mtSSU mS29, whose activity has been proposed to be linked to bridge formation between mtLSU and mtSSU, as in the case of MTG1 [ 4 ] [ 3 ].…”

YbeY is required for ribosome small subunit assembly and tRNA processing in human mitochondria

“…The assembly of mt-SSU and mt-LSU can be inextricably linked. It has been previously shown that defects in the assembly of the large subunit have negative consequences for the assembly of the small subunit (7,8). The knockout of YbeY leads to a severe depletion of mt-SSU.…”

“…The hydrolysis of NTPs by these enzymes ensure that the mt-rRNA does not fall into conformational traps. For example, GTPBP10 (also called ObgH2) (7,8), OBGH1 (also called GTPBP5) (9) and MTG1 (also called GTPBP7) (10) are three conserved GTPases that assist in the assembly of mt-LSU, and C4orf14 (11)(12)(13) and ERAL1 (14,15) are two conserved GTPases that are involved with the biogenesis of mt-SSU.…”

“…The assembly of mt-LSU can initiate on the 12S-16S mt-rRNA precursor molecule, but not the mt-SSU (21). The initiation and progression of small subunit assembly may be inhibited until a certain stage of early mt-LSU assembly is complete (8,22). Then, subsequent steps of mitoribosome biogenesis are continued in distinct foci called RNA granules (23,24).…”

Biogenese der mitochondrialen Proteinsynthesemaschine

“…mtLSU-Assemblierungsintermediaten nicht ersichtlich. Unsere Daten und die anderer Forschungsgruppen haben gezeigt, dass GTPBP10 für späte Reifungsprozesse der mtLSU notwendig ist [11,12]. Um die detaillierte Funktion von GTPBP10 zu definieren, werden strukturelle Analysen des GTPBP10-mtLSU-Komplexes notwendig sein.…”