Mancini-DiNardo Debora, Steele Scott J S, Ingram Robert S, Tilghman Shirley M
Howard Hughes Medical Institute and Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
Hum Mol Genet. 2003 Feb 1;12(3):283-94. doi: 10.1093/hmg/ddg024.
The imprinted gene cluster on mouse distal chromosome 7 contains a differentially methylated CpG island that maps within the Kcnq1 gene that has been shown to be required for the imprinting of multiple genes. To evaluate models for how this imprinting control region (ICR) regulates imprinting, we have characterized it structurally and functionally. We show that the region contains a promoter for a paternally expressed anti-sense transcript, Kcnq1ot1, and we define the extent of the minimal promoter. We describe three paternal-specific nuclease hypersensitive sites immediately upstream from the start site and show that they are required for full promoter activity. The expression of Kcnq1ot1 during pre- and postnatal development is compared to that of other imprinted genes in its vicinity, Cdnkn1c and Kcnq1. The lack of coordination in their expression tends to rule out an enhancer competition model for the action of the ICR in imprinting control. Using a stable transfection assay we show that the region contains a position-independent and orientation-independent silencer. We propose, on the basis of these findings, that the Kcnq1 ICR functions as a silencer on the paternal chromosome to effect the repression of neighboring genes.
小鼠7号远端染色体上的印记基因簇包含一个差异甲基化的CpG岛，该岛定位于Kcnq1基因内，已证明它是多个基因印记所必需的。为了评估这个印记控制区域（ICR）如何调控印记的模型，我们对其进行了结构和功能表征。我们发现该区域包含一个父本表达的反义转录本Kcnq1ot1的启动子，并确定了最小启动子的范围。我们描述了起始位点上游紧邻的三个父本特异性核酸酶超敏位点，并表明它们是启动子完全活性所必需的。将Kcnq1ot1在产前和产后发育期间的表达与附近其他印记基因Cdnkn1c和Kcnq1的表达进行了比较。它们表达缺乏协调性，这倾向于排除ICR在印记控制中作用的增强子竞争模型。使用稳定转染试验，我们表明该区域包含一个位置和方向独立的沉默子。基于这些发现，我们提出Kcnq1 ICR在父本染色体上作为沉默子发挥作用，以实现对邻近基因的抑制。
