Basu Amitava, Dasari Vasanthi, Mishra Rakesh K, Khosla Sanjeev
Centre for DNA Fingerprinting and Diagnostics (CDFD), Nampally, Hyderabad, India.
Centre for Cellular and Molecular Biology (CCMB), Council of Scientific and Industrial Research (CSIR), Hyderabad, India.
PLoS One. 2014 Apr 17;9(4):e93561. doi: 10.1371/journal.pone.0093561. eCollection 2014.
DNMT3L, a member of DNA methyltransferases family, is present only in mammals. As it provides specificity to the action of de novo methyltransferases, DNMT3A and DNMT3B and interacts with histone H3, DNMT3L has been invoked as the molecule that can read the histone code and translate it into DNA methylation. It plays an important role in the initiation of genomic imprints during gametogenesis and in nuclear reprogramming. With important functions attributed to it, it is imperative that the DNMT3L expression is tightly controlled. Previously, we had identified a CpG island within the human DNMT3L promoter and first exon that showed loss of DNA methylation in cancer samples. Here we show that this Differentially Methylated CpG island within DNMT3L (DNMT3L DMC) acts to repress transcription, is a Polycomb/Trithorax Response Element (PRE) and interacts with both PRC1 and PRC2 Polycomb repressive complexes. In addition, it adopts inactive chromatin conformation and is associated with other inactive chromatin-specific proteins like SUV39H1 and HP1. The presence of DNMT3L DMC also influences the adjacent promoter to adopt repressive histone post-translational modifications. Due to its association with multiple layers of repressive epigenetic modifications, we believe that PRE within the DNMT3L DMC is responsible for the tight regulation of DNMT3L expression and the aberrant epigenetic modifications of this region leading to DNMT3L overexpression could be the reason of nuclear programming during carcinogenesis.
DNMT3L是DNA甲基转移酶家族的成员之一,仅存在于哺乳动物中。由于它为从头甲基转移酶DNMT3A和DNMT3B的作用提供特异性,并与组蛋白H3相互作用,DNMT3L被认为是一种能够读取组蛋白密码并将其转化为DNA甲基化的分子。它在配子发生过程中的基因组印记起始以及核重编程中发挥着重要作用。鉴于其具有重要功能,DNMT3L的表达必须受到严格控制。此前,我们已经在人类DNMT3L启动子和第一个外显子内鉴定出一个CpG岛,该岛在癌症样本中显示出DNA甲基化缺失。在此我们表明,DNMT3L内的这个差异甲基化CpG岛(DNMT3L DMC)具有抑制转录的作用,是一个多梳/三胸反应元件(PRE),并与PRC1和PRC2多梳抑制复合物相互作用。此外,它呈现出无活性染色质构象,并与其他无活性染色质特异性蛋白如SUV39H1和HP1相关联。DNMT3L DMC的存在还会影响相邻启动子采用抑制性组蛋白翻译后修饰。由于它与多层抑制性表观遗传修饰相关联,我们认为DNMT3L DMC内的PRE负责DNMT3L表达的严格调控,而该区域导致DNMT3L过表达的异常表观遗传修饰可能是致癌过程中核编程的原因。