NSUN2 regulates PARP9 progression through m5C modification to mediate breast cancer progression.
BACKGROUND m5C modification plays a vital role in the progression of human cancers, including breast cancer (BC), but the function of NOP2/Sun RNA methyltransferase 2 (NSUN2), an RNA m5C modification enzyme, remains largely unclear. METHODS qRT-PCR, western blot and IHC assays were carried out to determine the expression of NSUN2, poly (ADP-ribose) polymerase 1 (PARP9) and Y box binding protein 1 (YBX1). EdU, flow cytometry, transwell, tube formation and sphere formation assays were conducted to evaluate cell proliferation, apoptosis, invasion, angiogenesis and stemness, respectively. ELISA was performed to examine the concentrations of inflammatory factors. RIP and pull-down assays were used to verify the interaction between NSUN2/YBX1 and PARP9. Murine xenograft model was constructed to explore the functions of NSUN2 and PARP9 in tumor growth in vivo. RESULTS PARP9 silencing suppressed the proliferation, invasion, angiogenesis, stemness and immune escape, and promoted apoptosis in BC cells in vitro. Mechanically, NSUN2 functioned as an m5C writer that catalyzed m5C modification of PARP9 mRNA, while YBX1 acted as an m5C reader that recognized the modified transcript and enhanced its stability, thereby elevating PARP9 expression in BC cells. YBX1 could elevate PARP9 expression in BC cells. Moreover, NSUN2 knockdown restrained the malignant behaviors of BC cells, with PARP9 overexpression restored the effects. In addition, NSUN2 knockdown blocked tumorigenesis in vivo by regulating PARP9 expression. CONCLUSION NSUN2-mediated m5C modification stabilizes PARP9 mRNA and is associated with enhanced BC progression and immune escape. The results broadened our understanding of the pathogenic mechanism of BC.