A novel DNMT3B splice variant expressed in tumor and pluripotent cells modulates genomic DNA methylation patterns and displays altered DNA binding.
A novel DNMT3B splice variant expressed in tumor and pluripotent cells modulates genomic DNA methylation patterns and displays altered DNA binding.
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DOI：
10.1158/1541-7786.mcr-09-0018
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发表时间：
2009-10
期刊：
影响因子：
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通讯作者：
Robertson KD
中科院分区：
文献类型：
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作者：
Gopalakrishnan S;Van Emburgh BO;Shan J;Su Z;Fields CR;Vieweg J;Hamazaki T;Schwartz PH;Terada N;Robertson KD
DNA甲基化是哺乳动物发育、基因组稳定性和印记必不可少的表观遗传标记。DNA甲基化模式由三种DNA甲基转移酶建立和维持：DNMT1、DNMT3a和Dnmt3b。有趣的是，这三个DNMT都使用了可选的剪接。Dnmt3b有近40个已知的剪接变异体，以组织和疾病特异性的方式表达，但对这些剪接变异体在调节Dnmt3b功能中的作用知之甚少。在这里，我们描述了一种新的选择性剪接形式的Dnmt3b，在N-末端调节域中缺少外显子5。这种变体，我们称之为DNMT3B3DNMT3B3Δ5，因为它在结构上与普遍表达的DNMT3B3亚型密切相关，在多能细胞和脑组织中高度表达，在分化过程中下调，并在小鼠中保守。从成纤维细胞产生多能诱导性多能性细胞可显著诱导DNMT3B3Δ5的表达。DNMT3B3DNMT3B3Δ5在人类疾病中的表达也发生变化，肿瘤细胞系根据其来源组织的不同而表现出表达上调或下调。比较DNMT3B3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B3DNMT3B在克隆形成实验中，异位过表达Δ5导致重复元件低甲基化，并促进细胞生长。综上所述，这些结果表明DNMT3B3DNMT3B3Δ5可能在干细胞的维持或分化中发挥重要作用，并提示外显子5编码的序列影响DNMT3b的功能特性。
DNA methylation is an epigenetic mark essential for mammalian development, genomic stability, and imprinting. DNA methylation patterns are established and maintained by three DNA methyltransferases: DNMT1, DNMT3A, and DNMT3B. Interestingly, all three DNMTs make use of alternative splicing. DNMT3B has nearly 40 known splice variants expressed in a tissue- and disease-specific manner, but very little is known about the role of these splice variants in modulating DNMT3B function. We describe here the identification and characterization of a novel alternatively spliced form of DNMT3B lacking exon 5 within the N-terminal regulatory domain. This variant, which we term DNMT3B3Δ5 because it is closely related in structure to the ubiquitously expressed DNMT3B3 isoform, is highly expressed in pluripotent cells and brain tissue, is downregulated during differentiation, and is conserved in the mouse. Creation of pluripotent iPS cells from fibroblasts results in marked induction of DNMT3B3Δ5. DNMT3B3Δ5 expression is also altered in human disease, with tumor cell lines displaying elevated or reduced expression depending on their tissue of origin. We then compared the DNA binding and subcellular localization of DNMT3B3Δ5 versus DNMT3B3, revealing that DNMT3B3Δ5 possessed significantly enhanced DNA binding affinity and displayed an altered nuclear distribution. Finally, ectopic overexpression of DNMT3B3Δ5 resulted in repetitive element hypomethylation and enhanced cell growth in a colony formation assay. Taken together, these results demonstrate that DNMT3B3Δ5 may play an important role in stem cell maintenance or differentiation and suggest that sequences encoded by exon 5 influence the functional properties of DNMT3B.