RPL37

RPL37 is an essential structural protein of the 60S large ribosomal subunit that also functions as a sensor and effector in the ribosomal stress–p53 surveillance pathway (PMID:1002715, PMID:20935493). It was first purified as a bona fide component of the rat liver large subunit and sequenced as a small (~96–111 residue) protein bearing a Cys40–Cys69 disulfide bridge and a C2-C2 zinc-finger motif (PMID:1002715, PMID:6350292, PMID:8484768). Beyond its ribosomal role, RPL37 couples ribosome integrity to p53: its mRNA is a 5'TOP transcript whose translation is positively controlled, with CK2-mediated phosphorylation of La protein limiting La binding to RPL37 mRNA and thereby promoting its polysome loading (PMID:15485924), and the m6A reader YTHDC1 enhancing RPL37 translation in an m6A-dependent manner (PMID:39725796). Under ribosomal stress and DNA damage by UV or cisplatin, RPL37 is degraded by the proteasome in the nucleoplasm, triggering L11-dependent inhibition of MDM2 and stabilization of p53, with consequent cell cycle arrest; conversely RPL37 overexpression attenuates the DNA-damage p53 response (PMID:20935493). Ectopic RPL37 directly binds MDM2 and inhibits its E3 ubiquitin ligase activity, stabilizing both MDM2 and p53 while downregulating MdmX through a mechanism distinct from RPS15 and RPS20 (PMID:23874713).

1. 1976 High

   Establishing whether L37 is a genuine ribosomal constituent rather than a co-purifying contaminant was the prerequisite for all later functional work; biochemical purification confirmed it as a structural subunit of the 60S particle.

   Evidence Stepwise LiCl/ion-exchange/Sephadex purification from rat liver 60S subunits with SDS-PAGE and amino acid composition

   PMID:1002715

   Open questions at the time

   • No sequence or structural placement within the subunit
   • No functional role beyond structural assignment
2. 1983 High

   The primary structure resolved the protein's covalent architecture, defining a 111-residue chain with an internal Cys40–Cys69 disulfide bridge and cross-kingdom homology, anchoring it within a conserved ribosomal protein family.

   Evidence Edman degradation and chemical cleavage peptide sequencing of rat liver L37

   PMID:6350292

   Open questions at the time

   • Functional consequence of the disulfide bridge unknown
   • No three-dimensional structure
3. 1993 Medium

   cDNA analysis refined the protein to 96 residues and identified a C2-C2 zinc-finger motif, raising the possibility of nucleic-acid or metal-dependent functions beyond structural scaffolding.

   Evidence cDNA sequencing and Southern blot copy-number analysis in rat

   PMID:8484768

   Open questions at the time

   • Zinc-binding and zinc-finger function not experimentally validated
   • Discrepancy in length versus protein-sequencing data unresolved
4. 1994 Medium

   Genetic dissection in yeast established RPL37 as essential, with duplicate differentially expressed loci, showing the gene is indispensable for viability.

   Evidence Gene disruption of RPL37A/RPL37B with reporter fusions and growth assays in S. cerevisiae

   PMID:8082197

   Open questions at the time

   • Essentiality in mammalian cells not directly tested here
   • Molecular basis of essentiality (assembly vs. translation) not defined
5. 1994 Low

   Cloning of the human ortholog provided the human coding sequence and predicted phosphorylation sites and a zinc finger, extending the rat findings to human.

   Evidence cDNA sequencing from human colon/liver tumor and normal tissue

   PMID:7545944

   Open questions at the time

   • Sequence-only analysis with no functional validation of phosphorylation sites or zinc finger
   • No demonstration of activity in human cells
6. 2004 Medium

   Identifying RPL37 mRNA as a 5'TOP target of La protein revealed a translational control node, showing CK2 phosphorylation of La regulates how much RPL37 message is loaded onto polysomes.

   Evidence CK2 inhibition (TBB), phospho-mutant La constructs, mRNA-protein association RT-PCR and polysome profiling

   PMID:15485924

   Open questions at the time

   • Physiological signals controlling CK2-La-RPL37 axis not mapped
   • Quantitative impact on ribosome biogenesis not measured
7. 2010 Medium

   Connecting RPL37 turnover to the p53 pathway recast it as a stress sensor: its nucleoplasmic proteasomal degradation under DNA damage drives L11-dependent MDM2 inhibition and p53 stabilization.

   Evidence siRNA knockdown, L11 epistasis, proteasome-inhibitor rescue and ectopic overexpression with p53 readouts in human cells

   PMID:20935493

   Open questions at the time

   • E3 ligase mediating RPL37 degradation not identified
   • Whether free vs. ribosomal RPL37 is degraded unresolved
8. 2013 Medium

   Demonstrating direct MDM2 binding defined RPL37 as an effector, not just a passive trigger, that inhibits MDM2 E3 activity and downregulates MdmX through a mechanism distinct from other ribosomal proteins.

   Evidence Ectopic expression in p53-null and p53-WT cells, Flag-MDM2/HA-p53 co-expression, E3 ligase activity assays

   PMID:23874713

   Open questions at the time

   • Structural basis of RPL37-MDM2 interaction not solved
   • Mechanism of MdmX downregulation not molecularly defined
   • Reconciliation with the degradation model of [#1] incomplete
9. 2024 Medium

   Adding a second translational regulator showed the m6A reader YTHDC1 boosts RPL37 translation, linking epitranscriptomic and hormonal (estradiol-RXRA) signaling to RPL37 output.

   Evidence RIP-seq, MeRIP-seq, knockdown/overexpression and ChIP-seq/luciferase assays in trophoblastic cells

   PMID:39725796

   Open questions at the time

   • Whether YTHDC1 control of RPL37 feeds the p53 axis untested
   • Generalization beyond trophoblastic cells unknown

• How the structural ribosomal role, the 5'TOP/m6A translational control, and the MDM2-p53 surveillance function are integrated within a single coherent regulatory circuit remains unresolved.
• No structure of RPL37 in the human 60S subunit or in complex with MDM2
• Identity of the stress-induced degradation machinery unknown
• Whether translational regulation modulates the p53 response not directly tested