The 40S ribosomal protein uS5 (RPS2) assembles into an extraribosomal complex with human ZNF277 that competes with the PRMT3–uS5 interaction

Abstract

Edited by Karin Musier-ForsythRibosomal (r)-proteins are generally viewed as ubiquitous, constitutive proteins that simply function to maintain ribosome integrity. However, findings in the past decade have led to the idea that r-proteins have evolved specialized functions beyond the ribosome. For example, the 40S ribosomal protein uS5 (RPS2) is known to form an extraribosomal complex with the protein arginine methyltransferase PRMT3 that is conserved from fission yeast to humans. However, the full scope of uS5's extraribosomal functions, including whether uS5 interacts with any other proteins, is not known. In this study, we identify the conserved zinc finger protein 277 (ZNF277) as a new uS5-associated protein by using quantitative proteomics approaches in human cells. As previously shown for PRMT3, we found that ZNF277 uses a C2H2-type zinc finger domain to recognize uS5. Analysis of protein-protein interactions in living cells indicated that the ZNF277-uS5 complex is found in the cytoplasm and the nucleolus. Furthermore, we show that ZNF277 and PRMT3 compete for uS5 binding, because overexpression of PRMT3 inhibited the formation of the ZNF277-uS5 complex, whereas depletion of cellular ZNF277 resulted in increased levels of uS5-PRMT3. Notably, our results reveal that ZNF277 recognizes nascent uS5 in the course of mRNA translation, suggesting cotranslational assembly of the ZNF277-uS5 complex. Our findings thus unveil an intricate network of evolutionarily conserved protein-protein interactions involving extraribosomal uS5, suggesting a key role for uS5 beyond the ribosome. . 2 The abbreviations used are: r-protein, ribosomal protein; ZNF277, zinc finger protein 277; PRMT3, protein arginine methyltransferase 3; uS5/RPS2, 40S ribosomal protein S2; ZF, zinc finger; SILAC, stable isotope labeling by amino acids in cell culture; PDCD2, programmed cell death protein 2; PDCD2L, PDCD2-like protein; AP, affinity purification; BiFC, bimolecular fluorescence complementation; YFP, yellow fluorescent protein; qPCR, quantitative PCR; MCS, multiple cloning site.

Zinc, an unexpected integrator of metabolism?

“…Furthermore, in Eukarya a number of ribosomal proteins also bind zinc‐finger regulators [see, e.g. (Dionne et al , 2019)]. This role must now be connected to the observation that in the model bacterium Bacillus subtilis a sophisticated regulatory circuit was recruited to optimize Zn 2+ acquisition and cellular distribution when the ion becomes limiting (Nies, 2019).…”

Tsr4 Is a Cytoplasmic Chaperone for the Ribosomal Protein Rps2 in Saccharomyces cerevisiae

“…Notably, Drosophila PDCD2/Zfrp8 copurifies with translation machinery, suggesting that cotranslational capture of Rps2 may be a conserved function of Tsr4 orthologs (41). Interestingly, the human zinc finger protein ZNF277 was identified as a cotranslational interactor of Rps2; however, knockdown of ZNF277 does not impair 40S production, suggesting that the ZNF277-Rps2 complex has a role outside ribosome biogenesis (56). Higher eukaryotic organisms appear to have evolved a more elaborate mechanism for handling Rps2 than that of S. cerevisiae and have even possibly adapted some extraribosomal functions for Rps2-containing complexes.…”

Exploiting codon usage identifies RpS21 as anin vivosignal strength-dependent Ras/MAPK regulator

“…A defect in RpS21 ribosomal function may trigger ribosomal biogenesis defects that alter translational fidelity or promote generation of oncoribosomes to preferentially express subset of mRNA pools 37,38 . Alternatively, RpS21 might also involve in other cellular processes independent of its canonical ribosomal function, as has been shown for other ribosomal subunits 39,40 .…”