ELF1-mediated transactivation of METTL3/YTHDF2 promotes nucleus pulposus cell senescence via m6A-dependent destabilization of E2F3 mRNA in intervertebral disc degeneration.

Intervertebral disc degeneration (IVDD) is a common pathology involving various degenerative diseases of the spine, with nucleus pulposus cell (NPC) senescence playing an important role in its pathogenesis. Transcriptional and epigenetic processes have been increasingly implicated in aging and longevity. E74-like factor 1 (ELF1) is a member of the erythroblast transformation specific family of proteins, which induce gene transcription by binding to gene promoters or enhancer sequences. However, the role of ELF1 in age-related diseases is unclear, with no reports of its involvement in NPC senescence or IVDD. ELF1 expression levels were assessed in human NP samples from IVDD patients, IVDD animal models, and naturally aged NP samples. Adeno-associated virus 5 (AAV5) vector-mediated Elf1 overexpressing mice and Elf1 knockout (KO) mice were used to investigate its role in NPC senescence and IVDD in vivo. The m6A methylase METTL3 and reading protein YTHDF2 were identified as downstream effectors of ELF1 using proteomic sequencing, RNA sequencing, ChIP-seq, promoter prediction, and binding analyses. MepRIP-qPCR, RNA pulldown, and double luciferase point mutation experiments revealed that METTL3 and YTHDF2 can recognize the m6A site on E2F3 mRNA, a key cell cycle gene. Finally, virtual screening techniques and various experiments were used to identify small molecule targets for ELF1 inhibition. ELF1 was found to drive m6A modification changes during NPC aging. The small molecule mycophenolate mofetil (MMF) could successfully target and inhibit ELF1 expression. In senescent NPCs, ELF1 can bind to the METTL3 and YTHDF2 gene promoter regions. Overexpressing METTL3 increased the E2F3 mRNA m6A modification abundance, while YTHDF2 was recruited to recognize this m6A site. This can accelerate the E2F3 mRNA degradation rate and ultimately lead to the onset of G1/S cell cycle arrest in NPC. For the first time, the transcription factor ELF1 has been identified as a novel regulator of NPC senescence and IVDD, which involves the ELF1-METTL3/YTHDF2-m6A-E2F3 axis. MMF, a small molecule designed to inhibit ELF1 and delay NPC senescence, was screened for the first time. This can potentially lead to new epigenetic therapeutic strategies for drug discovery and development for the clinical treatment of IVDD.