Control elements within the PWS/AS imprinting box and their function in the imprinting process
Control elements within the PWS/AS imprinting box and their function in the imprinting process
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DOI：
10.1093/hmg/ddh085
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发表时间：
2004-04-01
影响因子：
3.5
通讯作者：
Razin, A
中科院分区：
文献类型：
--
作者：
Kantor, B;Makedonski, K;Razin, A
人类染色体 15q11-q13（PWS/AS 结构域）上的一组印记基因及其小鼠 7c 号染色体上的同源基因被认为受到印记控制中心的调节。尽管天使曼综合征 (AS) 和普瑞德-威利综合征 (PWS) 患者中该区域的小缺失揭示了两个元素，分别是 AS 家族和 PWS 家族中重叠的最短缺失区域（AS-SRO 和 PWS-SRO），构成了 IC，但控制该区域控制的分子机制仍然不清楚。为了了解这个印记中心是如何工作的，我们寻找了小鼠模型。人类和小鼠序列之间惊人的相似性使得能够产生由 AS-SRO 和 Snrpn 最小启动子 (SMP)（PWS-SRO 的小鼠直向同源物）组成的小型转基因 (AS-SMP)。这种微型转基因以高度可靠和可重复的方式执行印记过程的所有步骤。为了破译印记过程的分子机制，我们生成并测试了基于 AS-SMP 的印记 5 个微型转基因，其中 160 bp SMP 的各个部分被删除。这些实验揭示了一组五个顺式元件，它们执行印记过程的各个步骤。该组包括：（i）两个从头甲基化信号（DNS）副本，在卵子发生过程中建立母体印记； (ii) 建立父系印记的等位基因辨别信号； (iii) 两个要素共同作用以维持父系印记。在各自的内源性小鼠序列上发现了两组功能冗余的五个元件，这解释了先前发表的靶向删除实验的矛盾结果。加上所有五种元素都结合特定蛋白质（这些蛋白质可能是印记过程中反式作用的因素）这一事实，我们的观察为全面研究印记过程控制所涉及的分子机制奠定了基础。
A cluster of imprinted genes on human chromosome 15q11-q13 (the PWS/AS domain) and its ortholog on mouse chromosome 7c is believed to be regulated by an imprinting control center. Although minideletions in this region in Angelman syndrome (AS) and Prader-Willi syndrome (PWS) patients revealed that two elements, shortest deletion regions of overlap in AS families and PWS families (AS-SRO and PWS-SRO), respectively, constitute the IC, the molecular mechanism that governs this regional control remains obscure. To understand how this imprinting center works, a mouse model was sought. The striking similarity between the human and mouse sequences allowed the generation of a minitransgene (AS-SMP) composed of AS-SRO and the Snrpn minimal promoter (SMP) the mouse ortholog of PWS-SRO. This minitransgene carries out, in a highly reliable and reproducible manner, all steps of the imprinting process. In an attempt to decipher the molecular mechanism of the imprinting process, we generated and tested for imprinting five minitransgenes based on AS-SMP, in which various parts of the 160 bp SMP were deleted. These experiments revealed a set of five cis elements that carry out the various steps of the imprinting process. This set includes: (i) two copies of a de novo methylation signal (DNS) that establish the maternal imprint during oogenesis; (ii) an allele discrimination signal that establishes the paternal imprint; and (iii) two elements that act together to maintain the paternal imprint. Two functionally redundant sets of the five elements were found on the respective endogenous mouse sequence explaining the previously published contradictory results of targeted deletion experiments. Together with the fact that all five elements bind specific proteins that are presumably the factors acting in trans in the imprinting process, our observations set the stage for a comprehensive study of the molecular mechanism involved in the control of the imprinting process.