Human Ribosomal Protein S3 Interacts with DNA Base Excision Repair Proteins hAPE/Ref-1 and hOGG1

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Abstract
The human ribosomal protein S3 (hS3) possesses associated activities that suggest alternative roles beyond its participation in protein translation. For example, it is capable of cleaving apurinic/apyrimidinic (AP) DNA via a β-elimination reaction, an activity that is missing in partially purified extracts of xeroderma pigmentosum group-D fibroblasts. In a recent study, we showed by surface plasmon resonance (SPR) that hS3 also has a very high apparent binding affinity for 7,8-dihydro-8-oxoguanine (8-oxoG) and AP sites in DNA. Using the same SPR technology, it is shown here that hS3 positively interacts with the human base excision repair (BER) enzymes N-glycosylase/AP lyase OGG1 and APE/Ref-1. Using a DNA substrate that allows for the detection of 8-oxoG repair, we also show that hOGG1 N-glycosylase activity becomes increasingly more robust in the presence of hS3. Human S3 was found to co-immunoprecipitate with both hOGG1 and APE/Ref-1, indicating that these proteins physically interact with one another. These results raise the possibility that hS3 not only functions as a ribosomal protein but, in addition, may influence repair activities at sites of DNA damage.