A novel oncomicropeptide encoded by DSP-AS1 exhibits proneoplastic properties in lung adenocarcinoma by facilitating YTHDF1-induced translation initiation through mediation of mRNA circularization

Functional micropeptides can hide inside RNA previously annotated as non-coding, their roles in the tumorigenesis of lung cancer remain largely unknown. Here, combining Ribo-seq, mass spectrometry and bioinformatics, we characterize a 46 amino-acid length oncogenic micropeptide encoded by lncRNA DSP-AS1, that we named Desmoplakin Associated MicroPeptide (DAMP), in lung adenocarcinoma (LUAD). DAMP is aberrantly overexpressed in LUAD and confers an unfavorable prognosis, its pro-neoplastic properties with respect to augmented proliferation, survival and invasiveness were validated in vitro and in vivo. DAMP colocalizes with translation machinery and induces translational reprogramming both by elevating global protein synthesis and by selectively upregulating the translation of mRNA group encoding oncogenic factors in LUAD. Mechanistically, DAMP simultaneously binds cap-binding subunit eIF4G and YTHDF1, a m6A reader that could fuel translation initiation by recruiting eIF3 to methylated mRNA. The above interactions lead to the formation of a “closed loop” between YTHDF1 and eIF4G bridged by DAMP, which makes YTHDF1 to be spatially in proximity with translation initiation complex and successfully loading of ribosomal 40S subunit onto target mRNAs. Targeting DAMP exhibited significant anti-cancer effects in vitro and in vivo. Our findings not only unravel the oncogenic role of a previously unrecognized micropeptide through orchestrating mRNA translation but also provide a strong rationale in the design of anti-cancer therapy targeting translation machinery in LUAD. Overall design: To identify lncRNAs with coding potential, we performed ribo-seq and paired mRNA seq in LUAD cell line H1975. To further clarify the mRNA regulated by novel peptide DAMP and investigate their translation dynamics, LUAD cell line H1975 with or without DAMP knockout were subjected to ribo-seq. Coupled mRNA-seq was carried out to control for the difference in ribosome-protected fragments due to differences in mRNA abundances resulting from altered RNA transcription.