Edwards Carol A, Ferguson-Smith Anne C
Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK.
Curr Opin Cell Biol. 2007 Jun;19(3):281-9. doi: 10.1016/j.ceb.2007.04.013. Epub 2007 Apr 27.
Clustered imprinted genes are regulated by differentially methylated imprinting control regions (ICRs) that affect gene activity and repression in cis over a large region. Although a primary imprint signal for each of these clusters is DNA methylation, different mechanisms are used to establish and maintain these marks. The majority of ICRs are methylated in the maternal germline and are usually promoters for antisense transcripts whose elongation is associated with imprinting control in the domain. In contrast, ICRs methylated in the paternal germline do not appear to act as promoters and are located between genes. At least one, at the Igf2/H19 locus, is known to function as an insulator. Analysis of ICRs suggests that maternal and paternal methylation imprints function in distinct ways.
成簇的印记基因由差异甲基化的印记控制区域（ICR）调控，这些区域在顺式作用下影响大片段区域内基因的活性和抑制。尽管这些基因簇中每个的主要印记信号都是DNA甲基化，但建立和维持这些印记的机制各不相同。大多数ICR在母系生殖系中发生甲基化，通常是反义转录本的启动子，其延伸与该区域的印记控制相关。相比之下，在父系生殖系中甲基化的ICR似乎并不作为启动子起作用，而是位于基因之间。已知至少有一个位于Igf2/H19基因座的ICR起到绝缘子的作用。对ICR的分析表明，母系和父系甲基化印记以不同的方式发挥作用。
