Domínguez-Bendala Juan, McWhir Jim
Roslin Institute, Roslin, Midlothian, Scotland EH25 9PS, UK.
Transgenic Res. 2004 Feb;13(1):69-74. doi: 10.1023/b:trag.0000017176.77847.80.
Increased methylation in promoter/enhancer regions typically results in transcriptional downregulation. The direct correlation between gene expression and homologous recombination (HR) is also widely acknowledged, and suggests that actively transcribed, hypomethylated targets may be more accessible to the HR machinery. Consistent with this hypothesis, we report that DNA methyltransferase 1 (Dnmt1)-knockout ES cells show a 2-fold increase in gene targeting frequency. However, the use of hypomethylated targeting vectors or the ectopic expression of a putative DNA demethylase did not enhance targeting frequency. These observations are discussed in the context of devising more efficient targeting protocols by transiently modifying genomic methylation levels.
启动子/增强子区域甲基化增加通常会导致转录下调。基因表达与同源重组（HR）之间的直接相关性也得到广泛认可，这表明活跃转录的低甲基化靶点可能更容易被HR机制作用。与该假设一致，我们报道DNA甲基转移酶1（Dnmt1）基因敲除的胚胎干细胞的基因打靶频率提高了2倍。然而，使用低甲基化打靶载体或假定的DNA去甲基化酶的异位表达并未提高打靶频率。在通过瞬时改变基因组甲基化水平设计更有效的打靶方案的背景下讨论了这些观察结果。
