MRPL35

MRPL35 (bL35m/mL38) is a mitospecific component of the mitochondrial ribosome large subunit, assembling into a subcomplex of the central protuberance together with partner proteins including Mrp7/bL27m (PMID:28931599). Rather than acting as a general translational subunit, it couples the synthesis of mitochondrially encoded OXPHOS subunits to their assembly: loss-of-function mrpL35 mutants display a cytochrome c oxidase assembly defect, mediated through the COX assembly factors Cox14 and Coa3, without a general block in mitochondrial protein synthesis (PMID:28931599). This assembly-coupling function localizes to a PEBP-homology domain, where invariant charged ligand-binding residues (Asp232, Arg288, Asp167) together with Arg127 of the neighboring Mrp7/bL27m form a microenvironment that renders newly synthesized proteins competent for OXPHOS assembly; mutating these residues impairs OXPHOS assembly while leaving translation intact (PMID:37792492). MRPL35 is incorporated during late large-subunit biogenesis, downstream of Mtg1-mediated restructuring of 21S rRNA helices and peptidyl transfer center maturation, coordinately with uL6m, uL16m, and bL36m (PMID:40865570). In mammalian cancer contexts, MRPL35 sustains proliferation and survival: its knockdown elevates ROS, inducing DNA damage, cell cycle arrest, and apoptosis (PMID:30862482), and it suppresses p53 signaling while maintaining cell cycle regulators (PMID:38093266). Its protein levels are stabilized by USP39-mediated deubiquitination, and it promotes SLC7A5-dependent glutamine metabolism (PMID:38987867).

1. 2017 Medium

   Establishing where MRPL35 physically sits in the mitoribosome and what it does there distinguished it from a generic ribosomal subunit, revealing a role in coupling translation to OXPHOS assembly.

   Evidence Biochemical subcomplex isolation in yeast mitochondria plus genetic analysis of respiratory-defective mrpL35 mutants and COX assembly intermediates

   PMID:28931599

   Open questions at the time

   • Mechanism by which the bL35m/Mrp7 subcomplex communicates with Cox14/Coa3 not resolved
   • Single lab
   • Not validated in mammalian mitoribosome
2. 2023 High

   Pinpointing the PEBP-homology domain charged residues showed the assembly-coupling activity is a discrete functional microenvironment separable from translation.

   Evidence Site-directed mutagenesis of PEBP-domain residues in yeast with parallel OXPHOS complex and translation rate readouts

   PMID:37792492

   Open questions at the time

   • Identity of any ligand bound by the PEBP pocket unknown
   • Structural mechanism of how the microenvironment confers assembly competency unresolved
3. 2025 High

   Defining the assembly hierarchy placed MRPL35 incorporation at a specific late step of large-subunit maturation downstream of rRNA refolding, clarifying biogenesis order.

   Evidence Cryo-EM of mtLSU assembly intermediates with genetic depletion of assembly factors and in vitro reconstitution in yeast

   PMID:40865570

   Open questions at the time

   • What triggers coordinate incorporation of bL35m with uL6m/uL16m/bL36m not defined
   • Mammalian assembly order not directly addressed
4. 2019 Medium

   Linking MRPL35 to ROS suppression in cancer cells established a pro-survival mitochondrial role beyond ribosome structure.

   Evidence siRNA knockdown in colorectal cancer cells with ROS, cell cycle, apoptosis, and membrane potential assays, plus NAC and overexpression rescue and xenograft

   PMID:30862482

   Open questions at the time

   • Molecular link between MRPL35 loss and ROS rise not mechanistically defined
   • Relationship to its mitoribosomal assembly function unexplored
5. 2021 Medium

   Proteomic profiling after knockdown nominated downstream effectors of MRPL35 in proliferation and survival.

   Evidence shRNA knockdown with iTRAQ proteomics and Western validation in gastric carcinoma cells plus xenograft

   PMID:33967557

   Open questions at the time

   • Whether PICK1/BCL-XL/AGR2 changes are direct or secondary unknown
   • No mechanistic connection to mitoribosome function
6. 2023 Medium

   Connecting MRPL35 to p53 suppression and cell cycle gene maintenance defined a transcriptional/signaling axis sustaining proliferation.

   Evidence Lentiviral shRNA knockdown in NSCLC cells with Western blot pathway readouts, colony formation, and xenograft imaging

   PMID:38093266

   Open questions at the time

   • How a mitoribosomal protein represses p53 signaling not established
   • Direct vs indirect regulation of cell cycle genes unresolved
7. 2023 Low

   Identifying a direct lncRNA partner raised the possibility of post-translational regulation of mitochondrial metabolic state via MRPL35.

   Evidence RNA-protein binding assay and metabolic profiling in macrophages in vitro and in vivo

   PMID:37545364

   Open questions at the time

   • Single binding interaction reported without detailed mechanistic follow-up on MRPL35's specific contribution
   • Functional consequence of the lncRNA-MRPL35 interaction not isolated
8. 2024 Medium

   Defining USP39-mediated stabilization and the SLC7A5/glutamine link placed MRPL35 in a deubiquitination-controlled metabolic circuit in cancer.

   Evidence Cellular ubiquitination assay, knockdown/overexpression, glutamine metabolism assays, and epistasis rescue with SLC7A5 in NSCLC cells plus xenograft

   PMID:38987867

   Open questions at the time

   • Mechanism by which MRPL35 regulates SLC7A5 expression unknown
   • Whether stabilization affects mitoribosomal vs metabolic functions not separated
9. 2025 Medium

   Gain-of-function in a cholestasis model extended the ROS-suppressing role of MRPL35 to control of hepatic inflammatory signaling.

   Evidence Adenovirus-mediated MRPL35 overexpression in a rat PNAC model with pathway protein readouts and NAC mechanistic control

   PMID:41049074

   Open questions at the time

   • Whether the anti-inflammatory effect derives from mitoribosomal function unclear
   • Upstream determinants of MRPL35 levels in this context undefined

• How the conserved mitoribosomal assembly-coupling function of MRPL35 mechanistically connects to its ROS-, p53-, and metabolism-modulating roles in mammalian cells remains unresolved.
• No study bridges the yeast structural/assembly mechanism with the mammalian cancer signaling phenotypes
• Endogenous ligand of the PEBP domain unidentified
• Direct molecular targets in p53 and SLC7A5 regulation not established