Jariwala Nidhi, Mendoza Rachel G, Garcia Dawn, Lai Zhao, Subler Mark A, Windle Jolene J, Mukhopadhyay Nitai D, Fisher Paul B, Chen Yidong, Sarkar Devanand
Department of Human and Molecular Genetics Virginia Commonwealth University Richmond VA.
Greehey Children's Cancer Research Institute University of Texas Health Science Center San Antonio San Antonio TX.
Hepatol Commun. 2019 Jul 15;3(9):1258-1270. doi: 10.1002/hep4.1400. eCollection 2019 Sep.
Oncoprotein staphylococcal nuclease and tudor domain containing 1 (SND1) regulates gene expression at a posttranscriptional level in multiple cancers, including hepatocellular carcinoma (HCC). Staphylococcal nuclease (SN) domains of SND1 function as a ribonuclease (RNase), and the tudor domain facilitates protein-oligonucleotide interaction. In the present study, we aimed to identify RNA interactome of SND1 to obtain enhanced insights into gene regulation by SND1. RNA interactome was identified by immunoprecipitation (IP) of RNA using anti-SND1 antibody from human HCC cells followed by RNA immunoprecipitation sequencing (RIP-Seq). Among RNA species that showed more than 10-fold enrichment over the control, we focused on the tumor suppressor protein tyrosine phosphatase nonreceptor type 23 (PTPN23) because its regulation by SND1 and its role in HCC are not known. PTPN23 levels were down-regulated in human HCC cells versus normal hepatocytes and in human HCC tissues versus normal adjacent liver, as revealed by immunohistochemistry. In human HCC cells, knocking down SND1 increased and overexpression of SND1 decreased PTPN23 protein. RNA binding and degradation assays revealed that SND1 binds to and degrades the 3'-untranslated region (UTR) of PTPN23 messenger RNA (mRNA). Tetracycline-inducible PTPN23 overexpression in human HCC cells resulted in significant inhibition in proliferation, migration, and invasion and tumorigenesis. PTPN23 induction caused inhibition in activation of tyrosine-protein kinase Met (c-Met), epidermal growth factor receptor (EGFR), Src, and focal adhesion kinase (FAK), suggesting that, as a putative phosphatase, PTPN23 inhibits activation of these oncogenic kinases. PTPN23 is a novel target of SND1, and our findings identify PTPN23 as a unique tumor suppressor for HCC. PTPN23 might function as a homeostatic regulator of multiple kinases, restraining their activation.
癌蛋白葡萄球菌核酸酶和含Tudor结构域蛋白1（SND1）在包括肝细胞癌（HCC）在内的多种癌症中，于转录后水平调节基因表达。SND1的葡萄球菌核酸酶（SN）结构域发挥核糖核酸酶（RNase）的功能，而Tudor结构域促进蛋白质与寡核苷酸的相互作用。在本研究中，我们旨在鉴定SND1的RNA相互作用组，以更深入了解SND1对基因的调控。通过使用抗SND1抗体对人肝癌细胞的RNA进行免疫沉淀（IP），随后进行RNA免疫沉淀测序（RIP-Seq）来鉴定RNA相互作用组。在比对照富集超过10倍的RNA种类中，我们重点关注肿瘤抑制蛋白非受体型23酪氨酸磷酸酶（PTPN23），因为其受SND1调控的情况及其在肝癌中的作用尚不清楚。免疫组织化学显示，与正常肝细胞相比，人肝癌细胞中PTPN23水平下调，与正常相邻肝脏组织相比，人肝癌组织中PTPN23水平也下调。在人肝癌细胞中，敲低SND1会使PTPN23蛋白增加，而SND1过表达则会使其减少。RNA结合和降解实验表明，SND1结合并降解PTPN23信使核糖核酸（mRNA）的3'非翻译区（UTR）。人肝癌细胞中四环素诱导的PTPN23过表达导致增殖、迁移、侵袭和肿瘤发生受到显著抑制。PTPN23的诱导导致酪氨酸蛋白激酶Met（c-Met）、表皮生长因子受体（EGFR）、Src和粘着斑激酶（FAK）的激活受到抑制，这表明作为一种假定的磷酸酶，PTPN23抑制这些致癌激酶的激活。PTPN23是SND1的一个新靶点，我们的研究结果确定PTPN23是肝癌独特的肿瘤抑制因子。PTPN23可能作为多种激酶的稳态调节因子，抑制它们的激活。
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