A Novel tsRNA, m7G-3' tiRNA LysTTT, Promotes Bladder Cancer Malignancy Via Regulating ANXA2 Phosphorylation.

Emerging evidence indicates that transfer RNA (tRNA)-derived small RNAs (tsRNAs), originated from tRNA with high abundance RNA modifications, play an important role in many complex physiological and pathological processes. However, the biological functions and regulatory mechanisms of modified tsRNAs in cancer remain poorly understood. Here, it is screened for and confirmed the presence of a novel m7G-modified tsRNA, m7G-3'-tiRNA LysTTT (mtiRL), in a variety of chemical carcinogenesis models by combining small RNA sequencing with an m7G small RNA-modified chip. Moreover, it is found that mtiRL, catalyzed by the tRNA m7G-modifying enzyme mettl1, promotes bladder cancer (BC) malignancy in vitro and in vivo. Mechanistically, mtiRL is found to specifically bind the oncoprotein Annexin A2 (ANXA2) to promote its Tyr24 phosphorylation by enhancing the interactions between ANXA2 and Yes proto-oncogene 1 (Yes1), leading to ANXA2 activation and increased p-ANXA2-Y24 nuclear localization in BC cells. Together, these findings define a critical role for mtiRL and suggest that targeting this novel m7G-modified tsRNA can be an efficient way for to treat BC.

Targeted m6A demethylation of ITGA6 mRNA by a multisite dCasRx-m6A editor inhibits bladder cancer development.

INTRODUCTION: N6-methyladenosine (m6A) modification contributes to the pathogenesis and development of various cancers, including bladder cancer (BCa). In particular, integrin α6 (ITGA6) promotes BCa progression by cooperatively regulating multisite m6A modification. However, the therapeutic effect of targeting ITGA6 multisite m6A modifications in BCa remains unknown. OBJECTIVES: We aim to develop a multisite dCasRx- m6A editor for assessing the effects of the multisite dCasRx-m6A editor targeted m6A demethylation of ITGA6 mRNA in BC growth and progression. METHODS: The multisite dCasRx- m6A editor was generated by cloning. m6A-methylated RNA immunoprecipitation (meRIP), luciferase reporter, a single-base T3 ligase-based qPCR-amplification, Polysome profiling and meRIP-seq experiments were performed to determine the targeting specificity of the multisite dCasRx-m6A editor. We performed cell phenotype analysis and used in vivo mouse xenograft models to assess the effects of the multisite dCasRx-m6A editor in BC growth and progression. RESULTS: We designed a targeted ITGA6 multi-locus guide (g)RNA and established a bidirectional deactivated RfxCas13d (dCasRx)-based m6A-editing platform, comprising a nucleus-localized dCasRx fused with the catalytic domains of methyltransferase-like 3 (METTL3-CD) or α-ketoglutarate-dependent dioxygenase alkB homolog 5 (ALKBH5-CD), to simultaneously manipulate the methylation of ITGA6 mRNA at four m6A sites. The results confirmed the dCasRx-m6A editor modified m6A at multiple sites in ITGA6 mRNA, with low off-target effects. Moreover, targeted m6A demethylation of ITGA6 mRNA by the multisite dCasRx-m6A editor significantly reduced BCa cell proliferation and migration in vitro and in vivo. Furthermore, the dCasRx-ALKBH5-CD and ITGA6 multi-site gRNA delivered to 5-week-old BALB/cJNju-Foxn1nu/Nju nude mice via adeno-associated viral vectors significantly inhibited BCa cell growth. CONCLUSION: Our study proposes a novel therapeutic tool for the treatment of BC by applying the multisite dCasRx-m6A editor while highlighting its potential efficacy for treating other diseases associated with abnormal m6A modifications.

TROP2 translation mediated by dual m6A/m7G RNA modifications promotes bladder cancer development.

RNA modifications, including adenine methylation (m6A) of mRNA and guanine methylation (m7G) of tRNA, are crucial for the biological function of RNA. However, the mechanism underlying the translation of specific genes synergistically mediated by dual m6A/m7G RNA modifications in bladder cancer (BCa) remains unclear. We demonstrated that m6A methyltransferase METTL3-mediated programmable m6A modification of oncogene trophoblast cell surface protein 2 (TROP2) mRNA promoted its translation during malignant transformation of bladder epithelial cells. m7G methyltransferase METTL1 enhanced TROP2 translation by mediating m7G modification of certain tRNAs. TROP2 protein inhibition decreased the proliferation and invasion of BCa cells in vitro and in vivo. Moreover, synergistical knockout of METTL3/METTL1 inhibited BCa cell proliferation, migration, and invasion; however, TROP2 overexpression partially abrogated its effect. Furthermore, TROP2 expression was significantly positively correlated with the expression levels of METTL3 and METTL1 in BCa patients. Overall, our results revealed that METTL3/METTL1-mediated dual m6A/m7G RNA modifications enhanced TROP2 translation and promoted BCa development, indicating a novel RNA epigenetic mechanism in BCa.