Epigenetic control of retrotransposon silencing in somatic cells of Drosohpila by the cytosine 5 Methyltransferase DNMT2

我们研究的中心目标在于解决DNMT2在果蝇模型系统中的表观遗传学功能。DNMT2参与逆转录转座子和重复依赖的基因沉默，通过白色报告基因的不同表达来监控。参与这些沉默过程的组蛋白甲基转移酶是SUV4-20和SETDB1，将研究DNMT2与这些酶在特定靶点的识别、结合和表观遗传索引功能上的相互依赖。首先，分离了DNMT2点突变，并对DNMT2在这些过程中的功能进行了系统的遗传剖析。利用芯片分析技术研究了DNMT2在早期胚胎发育过程中的表观遗传指标。DNMT2的表达水平强烈依赖于遗传背景。为了确定控制DNMT2表达的因素，将使用转基因表达报告系统对野生型种群进行遗传分析。除了分析逆转座子在控制依赖于DNMT2的沉默过程中的作用外，还将对一系列新发现的这些过程的修饰物的表观遗传学功能进行分子分析。将研究果蝇的TET1同源物是否在5-MC去甲基化中起作用。

The central aim of our studies consists in resolving the epigenetic function of DNMT2 in the Drosophila model system. DNMT2 is involved in retrotransposon and repeatdependent gene silencing monitored by variegated expression of the white reporter gene. Histone methyltransferases involved in these silencing processes are SUV4-20 and SETDB1 and functional interdependence of DNMT2 with these enzymes in recognition, binding and epigenetic indexing at specific target site will be studied. First Dnmt2 point mutations were isolated and systematic genetic dissection of DNMT2 function in these processes will be performed. Dnmt2 is very early zygotically expressed and its epigenetic indexing in early embryogenesis is studied by ChIP analysis. Dnmt2 expression levels strongly depend on the genetic background. For identification of factors controlling Dnmt2 expression wild type populations will be assayed using transgenic expression reporter systems for genetic analysis. Beside analysis of the role of retrotransposons in control of DNMT2 dependent silencing processes the epigenetic function of a series of newly identified modifiers of these processes will be molecularly analysed. It will be studied whether a putative TET1 homolog of Drosophila functions in demethylation of 5-mC.