Abstract 1358: Translational regulation of DNA repair: The mechanism under cap-independent translational regulation of RPA2

Abstract

Abstract Purpose: Maintenance of genome integrity is critical for any living cells. A variety of endogenous and exogenous factors can cause DNA damage. RPA2 (Replication protein A2) is a kind of single-stranded DNA binding protein complexes and play an important role in the DNA repair. Internal ribosome entry site (IRES) element is a RNA sequence with a complex structure, the activation of RPA2 IRES element can cause its abnormal expression and finally effects DNA repair pathway. IRES is regulated by eukaryotic translation initiation factors (eIFs) and IRES trans-acting factors (ITAFs). UNR (upstream of N-ras), as one of the important IRES trans-acting factors, and eIF3a (Eukaryotic initiation factor 3a) as one of the important eIFs play important roles in the regulation of RPA2 protein expression via IRES elements. We want to explore the role and potential mechanism of translational regulation of UNR and eIF3a in DNA repair. Methods: In the current study, biotin pull down assay was taken to investigate the interaction between RPA2 IRES and UNR. Western blot and qPCR were used to detect protein and mRNA level respectively. CO-IP assay were conducted for interaction of eIF3a with UNR. Immunofluorescence assay was taken to investigate the intracellular localization of UNR and eIF3a, as well as the regulation of UNR on DNA double strand break repair pathway. GST pull down assay was carried out to further identify the interaction between two proteins. Electrophoretic mobility shift assay was carried out to explore the domains of UNR and eIF3a that bind to RPA2 IRES element. Dual-luciferase reporter assay, comet assay and immunofluorescence assay were used to investigate the DNA repair pathway activity. Results: UNR and eIF3a translationally regulate RPA2 by combining with RPA2 IRES. It was found that the expression of RPA2 was down-regulated by UNR with no change on mRNA level. We further found that UNR combined with RPA2 IRES via CSD1 domain. And no domains of eIF3a bind to RPA2 IRES RNA.Meanwhile, the location of UNR and eIF3a was consistent. A series of assays indicate that CSD1 domain of UNR bind to PCI domain of. RPA2 play an important role in the DNA repair. We found that UNR down-regulated double-strand break repair (DSB) activity and nucleotide excision repair (NER) activity. Conclusion: UNR and eIF3a can regulate the expression of RPA2 on translational level, and further regulate the activity of DNA repair, which may reveal the potential mechanism of translational regulation and DNA repair. Citation Format: Jia-Jia Cui, Lei-Yun Wang, Ao-Xiang Guo, Ji-Ye Yin. Translational regulation of DNA repair: The mechanism under cap-independent translational regulation of RPA2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1358.