Role of m6A-dependent circRNAs during stress response in myeloid leukemic cells

The biological issue. N6-methyladenosine (m6A) is one of the most prevalent, abundant and conserved RNA modifications. It controls several biological processes, including also the biogenesis and function of circular RNAs (circRNAs), which are a class of covalently closed single-stranded RNAs. Recently, it has emerged a molecular interaction between the m6A RNA modification factors and the suppression of the proteotoxic stress response which induction is emerging as a relevant anticancer therapy in Acute Myeloid Leukemia (AML). Since proteasome inhibition, leading to imbalance in protein homeostasis, is strictly linked to the stress response induction, we decided to investigate the effect of Bortezomib (Btz) on m6A enzymes expression and its impact on the modulation of m6Adependent circRNAs expression. Results. In this thesis, we show that treatment of AML cells with Btz induces m6A enzymes downregulation at translation level. Moreover, we evidenced that this modulation is mediated by ROS generation and activation of the oxidative stress response. Indeed, administration of the reducing agent N-acetylcysteine inhibits Btz-mediated m6A enzymes downregulation. Moreover, despite the general decrease of m6A modification levels, we found that some circRNAs are more methylated and expressed upon Btz treatment compared to control samples. Conclusion. All together these data allow us to identify and investigate specific m6A-dependent circRNAs involved in the response to proteotoxic stress generated by Btz, in order to exploit them as molecular targets to improve Btz effectiveness in AML.