mA demethylation of FOSL1 mRNA protects hepatoma cells against necrosis under glucose deprivation.

Stress-adaptive mechanisms enabling cancer cells to survive under glucose deprivation remain elusive. N-methyladenosine (mA) modification plays important roles in determining cancer cell fate and cellular stress response to nutrient deficiency. However, whether mA modification functions in the regulation of cancer cell survival under glucose deprivation is unknown. Here, we found that glucose deprivation reduced mA modification levels. Increasing mA modification resulted in increased hepatoma cell necrosis under glucose deprivation, whereas decreasing mA modification had an opposite effect. Integrated mA-seq and RNA-seq revealed potential targets of mA modification under glucose deprivation, including the transcription factor FOSL1; further, glucose deprivation upregulated FOSL1 by inhibiting FOSL1 mRNA decay in an mA-YTHDF2-dependent manner through reducing mA modification in its exon1 and 5'-UTR regions. Functionally, FOSL1 protected hepatoma cells against glucose deprivation-induced necrosis in vitro and in vivo. Mechanistically, FOSL1 transcriptionally repressed ATF3 by binding to its promoter. Meanwhile, ATF3 and MAFF interacted via their leucine zipper domains to form a heterodimer, which competed with NRF2 for binding to antioxidant response elements in the promoters of NRF2 target genes, thereby inhibiting their transcription. Consequently, FOSL1 reduced the formation of the ATF3-MAFF heterodimer, thereby enhancing NRF2 transcriptional activity and the antioxidant capacity of glucose-deprived-hepatoma cells. Thus, FOSL1 alleviated the necrosis-inducing effect of glucose deprivation-induced reactive oxygen species accumulation. Collectively, our study uncovers the protective role of mA-FOSL1-ATF3 axis in hepatoma cell necrosis under glucose deprivation, and may provide new targets for cancer therapy.