The oncomicropeptide APPLE promotes hematopoietic malignancy by enhancing translation initiation

Mol Cell. 2021 Sep 15;S1097-2765(21)00713-9. doi: 10.1016/j.molcel.2021.08.033. Online ahead of print.

Abstract

Initiation is the rate-limiting step in translation, and its dysregulation is vital for carcinogenesis, including hematopoietic malignancy. Thus, discovery of novel translation initiation regulators may provide promising therapeutic targets. Here, combining Ribo-seq, mass spectrometry, and RNA-seq datasets, we discovered an oncomicropeptide, APPLE (a peptide located in ER), encoded by a non-coding RNA transcript in acute myeloid leukemia (AML). APPLE is overexpressed in various subtypes of AML and confers a poor prognosis. The micropeptide is enriched in ribosomes and regulates the initiation step to enhance translation and to maintain high rates of oncoprotein synthesis. Mechanically, APPLE promotes PABPC1-eIF4G interaction and facilitates mRNA circularization and eIF4F initiation complex assembly to support a specific pro-cancer translation program. Targeting APPLE exhibited broad anti-cancer effects in vitro and in vivo. This study not only reports a previously unknown function of micropeptides but also provides new opportunities for targeting the translation machinery in cancer cells.

Keywords: Micropeptide; PABPC1; cancer development; eIF4F complex assembly; eIF4G; leukemia; mRNA circularization; non-coding RNA (ncRNA); small open reading frame (ORF); translation initiation.