Theranostics 2020; 10(10):4437-4452. doi:10.7150/thno.42047

Research Paper

PRMT5-dependent transcriptional repression of c-Myc target genes promotes gastric cancer progression

Ming Liu1*, Bing Yao1,2*, Tao Gui1*, Chan Guo1, Xiaobin Wu3, Jiahuang Li1, Lingling Ma1, Yexuan Deng1, Peipei Xu1, Ying Wang1, Dongjun Yang1, Qixiang Li1, Xiangwei Zeng1, Xinyu Li1, Ruifeng Hu1, Jingru Ge1, Zenong Yu1, Yugen Chen3, Bing Chen1, Junyi Ju1✉, Quan Zhao1✉

1. The State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Institute of Translational Medicine, School of Life Sciences, Nanjing University, Nanjing, China
2. Department of Medical Genetics, Nanjing Medical University, Nanjing, China
3. The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing, China
*Ming Liu, Bing Yao, Tao Gui contributed equally to this work.

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Citation:
Liu M, Yao B, Gui T, Guo C, Wu X, Li J, Ma L, Deng Y, Xu P, Wang Y, Yang D, Li Q, Zeng X, Li X, Hu R, Ge J, Yu Z, Chen Y, Chen B, Ju J, Zhao Q. PRMT5-dependent transcriptional repression of c-Myc target genes promotes gastric cancer progression. Theranostics 2020; 10(10):4437-4452. doi:10.7150/thno.42047. Available from http://www.thno.org/v10p4437.htm

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Abstract

The proto-oncogene c-Myc regulates multiple biological processes mainly through selectively activating gene expression. However, the mechanisms underlying c-Myc-mediated gene repression in the context of cancer remain less clear. This study aimed to clarify the role of PRMT5 in the transcriptional repression of c-Myc target genes in gastric cancer.

Methods: Immunohistochemistry was used to evaluate the expression of PRMT5, c-Myc and target genes in gastric cancer patients. PRMT5 and c-Myc interaction was assessed by immunofluorescence, co-immunoprecipitation and GST pull-down assays. Bioinformatics analysis, immunoblotting, real-time PCR, chromatin immunoprecipitation, and rescue experiments were used to evaluate the mechanism.

Results: We found that c-Myc directly interacts with protein arginine methyltransferase 5 (PRMT5) to transcriptionally repress the expression of a cohort of genes, including PTEN, CDKN2C (p18INK4C), CDKN1A (p21CIP1/WAF1), CDKN1C (p57KIP2) and p63, to promote gastric cancer cell growth. Specifically, we found that PRMT5 was required to promote gastric cancer cell growth in vitro and in vivo, and for transcriptional repression of this cohort of genes, which was dependent on its methyltransferase activity. Consistently, the promoters of this gene cohort were enriched for both PRMT5-mediated symmetric di-methylation of histone H4 on Arg 3 (H4R3me2s) and c-Myc, and c-Myc depletion also upregulated their expression. H4R3me2s also colocalized with the c-Myc-binding E-box motif (CANNTG) on these genes. We show that PRMT5 directly binds to c-Myc, and this binding is required for transcriptional repression of the target genes. Both c-Myc and PRMT5 expression levels were upregulated in primary human gastric cancer tissues, and their expression levels inversely correlated with clinical outcomes.

Conclusions: Taken together, our study reveals a novel mechanism by which PRMT5-dependent transcriptional repression of c-Myc target genes is required for gastric cancer progression, and provides a potential new strategy for therapeutic targeting of gastric cancer.

Keywords: PRMT5, c-Myc, gastric cancer, histone arginine methylation, tumorigenesis