本文選題：PRMT7 + 自甲基化修飾��； 參考：《東北師范大學》2017年博士論文

【摘要】：蛋白質的翻譯后修飾是表觀遺傳學研究的核心領域之一,主要包括磷酸化修飾、乙酰化修飾、甲基化修飾、SUMO化修飾和泛素化修飾等。蛋白質的翻譯后修飾的改變通常都能夠影響蛋白質的活性和功能。精氨酸甲基化是一種普遍存在的翻譯后修飾,由蛋白精氨酸甲基轉移酶(Protein Arginine Methyltransferases,PRMTs)催化,將甲基基團從甲基供體(S-腺苷甲硫氨酸)上轉移到精氨酸殘基胍基的氮原子上。蛋白質精氨酸甲基化修飾可以激活或抑制基因的轉錄;參與細胞信號轉導、細胞代謝、蛋白質穩(wěn)定性和DNA損傷修復等過程。近些年的研究表明,異常的精氨酸甲基化修飾與多種疾病密切相關,特別是癌癥。PRMT7是發(fā)現(xiàn)較晚的PRMTs家族成員,在基因組印記、DNA損傷應答以及細胞分化等過程中發(fā)揮著重要的作用。我們以前的研究工作發(fā)現(xiàn),PRMT7在惡性程度高的乳腺癌組織和高轉移的乳腺癌細胞中高表達。上調的PRMT7增加了E-cadherin啟動子處抑制基因表達的H4R3me2s修飾水平;降低了激活基因表達的H3K4me3修飾水平,組蛋白H3和組蛋白H4的乙酰化修飾水平,抑制E-cadherin的表達。PRMT7的高表達,打破了組蛋白精氨酸甲基化修飾、組蛋白賴氨酸甲基化修飾和組蛋白乙酰化修飾之間的平衡,導致細胞間粘附分子E-cadherin的表達降低,誘發(fā)乳腺癌細胞發(fā)生上皮細胞間質細胞轉換(Epithelial-Mesenchymal Transition,EMT),促進乳腺癌的轉移。在本課題的研究中,我們發(fā)現(xiàn)PRMT7的第531位精氨酸(PRMT7 R531)在體外和體內均可以發(fā)生自甲基化修飾;PRMT7的自甲基化修飾對于PRMT7所介導的EMT及乳腺癌細胞的遷移和侵襲是必須的;利用CRISPR/Cas9技術敲除高轉移的MDA-MB-231細胞中本底表達的PRMT7后,細胞的遷移和侵襲能力明顯下降,然而再外源過表達野生型的PRMT7恢復了細胞的遷移和侵襲能力,而再外源過表達自甲基化修飾位點突變的PRMT7則沒有;隨后,小鼠肺轉移實驗證實,PRMT7 WT同PRMT7R531K相比,明顯地促進了乳腺癌細胞MCF7的遠端轉移;進一步,免疫組化實驗顯示高表達的甲基化的PRMT7與臨床的乳腺癌樣本具有一定的相關性,50%III期乳腺癌樣本呈現(xiàn)出高表達的甲基化的PRMT7,47.2%三陰性乳腺癌(TNBC)樣本中呈現(xiàn)出甲基化的PRMT7的高表達。進一步研究表明,PRMT7的自甲基化修飾增強了PRMT7與轉錄因子YY1之間的相互作用能力,從而增加了PRMT7到E-cadherin啟動子處的招募,導致H4R3me2s水平升高,H3K4me3水平降低,從而抑制E-cadherin的表達,促進乳腺癌轉移。綜上,我們發(fā)現(xiàn)了PRMT7蛋白的一種新的翻譯后修飾-自甲基化修飾,這種自甲基化修飾與乳腺癌轉移密切相關。該研究為以PRMT7作為乳腺癌治療的新靶標提供了新的理論基礎和實驗依據。
[Abstract]:Posttranslational modification of proteins is one of the core areas of epigenetics, including phosphorylation modification, acetylation modification, methylation modification, sumo modification and ubiquitin modification. Changes in post-translational modification of proteins usually affect the activity and function of proteins. Arginine methylation is a common posttranslational modification catalyzed by protein Arginine Methyltransferasesl PRMTs, which transports the methyl group from the methyl donor S- adenosine methionine to the nitrogen atom of the arginine residue guanidine. Protein arginine methylation can activate or inhibit gene transcription, participate in cell signal transduction, cell metabolism, protein stability and DNA damage repair. Recent studies have shown that abnormal arginine methylation is closely associated with many diseases, especially cancer. PRMT7 is a member of the PRMTs family that was discovered later. It plays an important role in DNA damage response and cell differentiation of genomic imprinting. Our previous studies have found that PRMT7 is highly expressed in breast cancer tissues with high malignancy and in breast cancer cells with high metastasis. The up-regulated PRMT7 increased the H4R3me2s modification level of inhibiting gene expression at the E-cadherin promoter, decreased the H3K4me3 modification level of activating gene expression, the acetylation modification level of histone H3 and histone H4, and inhibited the overexpression of E-cadherin. The balance between histone arginine methylation modification, histone lysine methylation modification and histone acetylation modification was broken, and the expression of intercellular adhesion molecule E-cadherin was decreased. Epithelial-mesenchymal transition (EMT) was induced in breast cancer cells to promote the metastasis of breast cancer. In this study, we found that the self-methylation modification of PRMT7 is necessary for the migration and invasion of EMT and breast cancer cells mediated by PRMT7, both in vitro and in vivo. The ability of migration and invasion of MDA-MB-231 cells was significantly decreased after knockout of background expression of PRMT7 in MDA-MB-231 cells with high metastasis by CRISPR/Cas9 technique. However, the ability of migration and invasion was restored by overexpression of wild type PRMT7. However, PRMT7, which was overexpression of automethylation modification site mutation, was not. Subsequently, the mouse lung metastasis test confirmed that PRMT7WT significantly promoted the distal metastasis of MCF7 in breast cancer cells compared with PRMT7R531K. Immunohistochemical analysis showed that high expression of methylated PRMT7 was associated with clinical breast cancer samples. The high expression of methylated PRMT7 was found in 47.2% tri-negative breast cancer samples with high methylation in phase III breast cancer samples. Further studies showed that the self-methylation of PRMT7 enhanced the interaction between PRMT7 and transcription factor YY1, increased the recruitment of PRMT7 to E-cadherin promoter, increased the level of H4R3me2s and decreased the level of H3K4me3, thus inhibited the expression of E-cadherin. Promote metastasis of breast cancer. In conclusion, we have found a new posttranslational modification of PRMT7 protein, self-methylation modification, which is closely related to breast cancer metastasis. This study provides a new theoretical and experimental basis for using PRMT7 as a new target for breast cancer treatment.
【學位授予單位】：東北師范大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：R737.9

【參考文獻】

相關期刊論文 前1條

1 Zhao-ji LIU;Gregg L.SEMENZA;Hua-feng ZHANG;;低氧誘導因子與乳腺癌轉移(英文)[J];Journal of Zhejiang University-Science B(Biomedicine & Biotechnology);2015年01期

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本文編號：1835614