m5C RNA modification upregulates E2F1 expression dependently on YBX1 phase separation and promotes tumor progression in ovarian cancer

Abstract

Abstract 5-methylcytosine (m5C) is a common RNA modification that modulates gene expression at the post-transcriptional level, but the cross-talk between m5C RNA modification and biomolecule condensation as well as transcription factor-mediated transcriptional regulation in ovarian cancer remains poorly understood. In this study, we uncover that the RNA methytransferase NSUN2 facilitates m5C modification of mRNA and forms a positive feedback regulatory loop with the transcription factor E2F1 in ovarian cancer. Specifically, NSUN2 promotes m5C modification of E2F1 mRNA and enhances its stability, and E2F1 binds to NSUN2 promoter followed by the activated transcription reciprocally. The RNA binding protein YBX1 acts as the m5C reader and is involved in NSUN2-mediated E2F1 regulation. m5C modification promotes YBX1 phase separation that upregulates E2F1 expression. In ovarian cancer, NSUN2 and YBX1 are amplified and upregulated, and higher expressions of NSUN2 and YBX1 predict a worse prognosis for ovarian cancer patients. Moreover, E2F1 transcriptionally regulates the expression of oncogenes MYBL2 and RAD54L, driving ovarian cancer progression. Thus, our study delineates a NSUN2-E2F1-NSUN2 circuitry regulated by m5C modification dependently on YBX1 phase separation, and the identified previously unknown pathway can be a promising target for ovarian cancer treatment.