Inflammatory cytokine–regulated tRNA-derived fragment tRF-21 suppresses pancreatic ductal adenocarcinoma progression
Ling Pan, … , Dongxin Lin, Jian Zheng
Ling Pan, … , Dongxin Lin, Jian Zheng
Published November 15, 2021
Citation Information: J Clin Invest. 2021;131(22):e148130. https://doi.org/10.1172/JCI148130.
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Inflammatory cytokine–regulated tRNA-derived fragment tRF-21 suppresses pancreatic ductal adenocarcinoma progression

Abstract

The tumorigenic mechanism for pancreatic ductal adenocarcinoma (PDAC) is not clear, although chronic inflammation is implicated. Here, we identified an inflammatory cytokine–regulated transfer RNA–derived (tRNA-derived) fragment, tRF-21-VBY9PYKHD (tRF-21), as a tumor suppressor in PDAC progression. We found that the biogenesis of tRF-21 could be inhibited by leukemia inhibitory factor and IL-6 via the splicing factor SRSF5. Reduced tRF-21 promoted AKT2/1-mediated heterogeneous nuclear ribonucleoprotein L (hnRNP L) phosphorylation, enhancing hnRNP L to interact with dead-box helicase 17 (DDX17) to form an alternative splicing complex. The provoked hnRNP L-DDX17 activity preferentially spliced Caspase 9 and mH2A1 pre-mRNAs to form Caspase 9b and mH2A1.2, promoting PDAC cell malignant phenotypes. The tRF-21 levels were significantly lower in PDACs than in normal tissues, and patients with low tRF-21 levels had a poor prognosis. Treatment of mouse PDAC xenografts or patient-derived xenografts (PDXs) with tRF-21 mimics repressed tumor growth and metastasis. These results demonstrate that tRF-21 has a tumor-suppressive effect and is a potential therapeutic agent for PDAC.

Authors

Ling Pan, Xudong Huang, Ze-Xian Liu, Ying Ye, Rui Li, Jialiang Zhang, Guandi Wu, Ruihong Bai, Lisha Zhuang, Lusheng Wei, Mei Li, Yanfen Zheng, Jiachun Su, Junge Deng, Shuang Deng, Lingxing Zeng, Shaoping Zhang, Chen Wu, Xu Che, Chengfeng Wang, Rufu Chen, Dongxin Lin, Jian Zheng

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Figure 3

tRF-21 interacts with hnRNP L at Ser52.

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tRF-21 interacts with hnRNP L at Ser52. (A) Schematic of the RNA-pulldo...
(A) Schematic of the RNA-pulldown assay followed by liquid chromatography-mass spectrometry (LC-MS) using a tRF-21 sense or antisense probe for the identification of proteins that specifically bind tRF-21. (B) Western blot analysis of products from RNA-pulldown assays using tRF-21, tRF-21 antisense, or a nontargeting oligo suggested 7 potential tRF-21–binding proteins. (C) Association of hnRNP L with tRF-21 in PDAC cells determined by RIP assays followed by qRT-PCR or Northern blotting. qRT-PCR data represent enrichment (mean ± SEM) relative to input from 3 independent experiments. IgG was used as a negative control. (D) tRF-21 overexpression or silencing did not affect HNRNPL mRNA or protein levels. qRT-PCR data indicate the mean ± SEM of 3 independent experiments. (E) Truncation mapping of the tRF-21–hnRNP L binding domain. Schematic diagram shows the FLAG-tagged hnRNP L protein domain structure. Western blot (WB) shows FLAG-tagged full-length (WT) hnRNP L and its truncated forms pulled down by tRF-21. (F) Schematic of phosphorylation sites in the Gly-rich domain; Ser52 is responsible for the activation of hnRNP L. (G) Immunoblot (IB) shows FLAG-tagged full-length hnRNP L (WT) and its mutated forms (Y47F, Y48F, and S52A) retrieved by tRF-21. (H) RIP assays with an antibody against FLAG showed that FLAG-Y47F and FLAG-Y48F, but not FLAG-S52A, interacted with tRF-21. Data represent enrichment (mean ± SEM) relative to input from 3 independent experiments. IgG was used as a negative control. (I) Predicted 3D structure of the hnRNPL–tRF-21 complex. **P < 0.01 and ***P < 0.001, by 1-way ANOVA with Dunnett’s T3 multiple-comparison test (C, D, and H).