Apurinic/Apyrimidinic Endodeoxyribonuclease 1 (APEX1)promotes Stress Granule Formation Via YBX1 Phosphorylation

Ovarian cancer is a malignant tumor that develops in the ovaries.In its early stages,ovarian cancer often lacks obvious symptoms,making it difficult to diagnose.Therefore,it is considered the second leading cause of death among gynecological cancers.APEX1 is an important gene involved in DNA damage repair,redox regulation of transcriptional factors,and is widely involved in processes such as cellular stress response,cancer metastasis,drug resistance,and immune response.APEX1 shows high expression in ovarian cancer tissues and is associated with poor prognosis.However,it is unclear how APEX1 regulates cell resistance to drugs and other environmental stresses.Stress granules(SGs)are ribonucleoprotein(RNP)granules that cells form in face of stress.They are membrane-less structures assembled by the interaction of RNA molecules and RNA-binding proteins(RBPs)via liquid-liquid phase separation(LLPS),which mainly functions to inhibit transcription.The timely assembly and disassembly of stress granules are crucial for cell survival.Previous studies suggest that SG dynamics is tightly regulated by post-translational modifications(PTMs),particularly protein phosphorylation.However,no research has explored how APEX1 engages in stress granule regulation nor its roles in the phosphorylation of stress granule componants.In this study,we found that APEX1 was overexpressed in the ovarian cancer tissues of patients with cisplatin resistance and that it promoted stress granule formation in cells.We reveal that APEX1 colocalizes to stress granules where it interacts with YBX1 and G3BP1.Through phosphoproteomic profiling,we demonstrate that APEX1 profoundly alteres the phospholandscape of ovarian cancer cell line SKOV3,especially the phosphor-profile of stress granulerelated proteins.These proteins include important stress granule components such as G3BP2,EIF5 and YBX1.These changes may stem from APEX1’s impact on kinases and kinase signaling pathways.Furthermore,We reveal that the dual phosphorylation of the SG protein YBX1 at S174/S176 is significantly elevated by APEX1.Our study suggests that APEX1 can promote SG formation,and hence cell survival,by promoting the dual phosphorylation of YBX1.Therefore,we propose a model in which APEX1 regulates cellular stress response.In conjunction with its known roles in BER and transcriptional regulation,APEX1 profoundly affects the phosphoproteome of cells,including kinase signaling pathways and protein kinases such as AKT1,AKT2 and MAPK14.Modulation in kinase signaling pathways in turn significantly modifies the phosphoprofile of SG proteins.Among these,APEX1 promotes YBX1 phosphorylation at S174 and S176 to enhance SG formation and cell survival.In summary,our research has demonstrated the significant role of APEX1 in ovarian cancer development and drug resistance.We reveal that APEX1 not only localizes to stress granules(SG),but also modulates the phospho-landscape of cells and the phsophoprofile of SG proteins.In particular,it promotes dual phosphorylation of YBX1 at S174/176 to facilitate SG formation,thus promoting cellular stress response and survival.Our study provides a foundation for future cancer treatments targeting stress granules through APEX1 and YBX1.