C. elegans ribosomal protein S3 protects against H₂O₂-induced DNA damage and suppresses spontaneous mutations in yeast

Carcinogenicity and cytotoxicity are severe consequences of DNA damage. Base Excision Repair (BER) is a conserved DNA repair pathway that replaces many damaged bases caused by oxidation. Aberrations in BER are associated with carcinogenesis, neurodegeneration, and aging. The nematode C. elegans is an attractive model system for studying BER. However, in this organism, the complete pathway is not fully delineated. To further explore the BER process in C. elegans, we used affinity tag chromatography and mass spectrometry to identify the interactome of uracil DNA glycosylase-1 (CeUNG-1), an enzyme that acts during the first step of the BER pathway. Our analysis identified that CeUNG-1 is associated with the 40 S ribosomal protein S3 (CeRPS-3), homologs of which have been shown to process 8-oxoguanine and abasic site lesions in other organisms. We report a strong in silico association between CeUNG-1 and CeRPS-3 and confirmed this interaction using the yeast two-hybrid system. Downregulation of the Cerps-3 gene reduced the viability of wild-type worms upon exposure to the chemical oxidant hydrogen peroxide. Further analysis shows that Cerps-3 knockdown significantly sensitized the AP endonuclease APN-1-deficient strain, apn-1, but to a lesser extent exo-3, to the lethal effects of hydrogen peroxide. A cross-species complementation experiment reveals that the expression of CeRPS-3 rescued the hydrogen peroxide sensitivity, and suppressed the high mutation frequency of the yeast AP endonuclease-deficient strain lacking Apn1 and Apn2. We propose that CeRPS-3 may function as an auxiliary DNA repair enzyme in C. elegans to process oxidative DNA lesions.