PRMT5-dependent transcriptional repression of c-Myc target genes promotes gastric cancer progression
PRMT5-dependent transcriptional repression of c-Myc target genes promotes gastric cancer progression
复制标题
PRMT5依赖性c-Myc靶基因转录抑制促进胃癌进展
DOI：
10.7150/thno.42047
复制
发表时间：
2020-01-01
期刊：
影响因子：
12.4
通讯作者：
Zhao, Quan
中科院分区：
文献类型：
--
作者：
Liu, Ming;Yao, Bing;Zhao, Quan
原癌基因c-Myc主要通过选择性激活基因表达来调节多种生物学过程。然而，在癌症背景下，c-Myc介导的基因抑制的潜在机制仍然不太清楚。本研究旨在阐明PRMT5在胃癌c-Myc靶基因转录抑制中的作用。方法：应用免疫组织化学方法检测PRMT5、c-Myc和靶基因在胃癌组织中的表达。免疫荧光法、免疫共沉淀法和GST下拉试验检测PRMT5和c-Myc的相互作用。通过生物信息学分析、免疫印迹、实时定量聚合酶链式反应、染色质免疫沉淀和挽救实验对其作用机制进行了评价。结果：c-Myc直接与精氨酸甲基转移酶5(PRMT5)相互作用，在转录水平抑制PTEN、CDKN2C(P18INK4C)、CDKN1A(p21CIP1/WAF1)、CDKN1C(P57Kip2)和p63等基因的表达，促进胃癌细胞生长。具体地说，我们发现PRMT5在体外和体内都需要促进胃癌细胞的生长，并需要依赖于其甲基转移酶活性来转录抑制这组基因。该基因的启动子富含PRMT5介导的组蛋白H4在Arg3上的对称双甲基化(H4R3me2s)和c-Myc，c-Myc缺失也上调了它们的表达。H4R3me2s还与这些基因上的c-Myc结合E盒基序(CANNTG)共定位。我们发现PRMT5直接与c-Myc结合，这种结合是转录抑制靶基因所必需的。C-Myc和PRMT5在原发胃癌组织中表达上调，其表达水平与临床预后呈负相关。结论：我们的研究揭示了依赖PRMT5的c-Myc靶基因转录抑制在胃癌进展中的新机制，并为胃癌的靶向治疗提供了一种潜在的新策略。
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.