Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America.
PLoS One. 2012;7(1):e30437. doi: 10.1371/journal.pone.0030437. Epub 2012 Jan 19.
P-element vectors are commonly used to make transgenic Drosophila and generally insert in the genome in a nonselective manner. However, when specific fragments of regulatory DNA from a few Drosophila genes are incorporated into P-transposons, they cause the vectors to be inserted near the gene from which the DNA fragment was derived. This is called P-element homing. We mapped the minimal DNA fragment that could mediate homing to the engrailed/invected region of the genome. A 1.6 kb fragment of engrailed regulatory DNA that contains two Polycomb-group response elements (PREs) was sufficient for homing. We made flies that contain a 1.5 kb deletion of engrailed DNA (en(Δ1.5)) in situ, including the PREs and the majority of the fragment that mediates homing. Remarkably, homing still occurs onto the en(Δ1. 5) chromosome. In addition to homing to en, P[en] inserts near Polycomb group target genes at an increased frequency compared to P[EPgy2], a vector used to generate 18,214 insertions for the Drosophila gene disruption project. We suggest that homing is mediated by interactions between multiple proteins bound to the homing fragment and proteins bound to multiple areas of the engrailed/invected chromatin domain. Chromatin structure may also play a role in homing.
P 元素载体常用于制作转基因果蝇，通常以非选择性的方式插入基因组中。然而，当少数果蝇基因的特定调控 DNA 片段被整合到 P-转座子中时，它们会导致载体插入到 DNA 片段来源的基因附近。这称为 P 元素归巢。我们将介导归巢的最小 DNA 片段定位到基因组的 engrailed/invected 区域。含有两个 Polycomb 组反应元件 (PRE) 的 engrailed 调控 DNA 的 1.6 kb 片段足以介导归巢。我们制作了原位含有 engrailed DNA（en(Δ1.5)）缺失的果蝇，包括 PRE 和介导归巢的大多数片段。值得注意的是，归巢仍然发生在 en(Δ1.5) 染色体上。与用于生成果蝇基因敲除项目的 18,214 个插入的载体 P[EPgy2]相比，P[en] 插入 Polycomb 组靶基因的频率增加，除了归巢到 en 之外。我们认为归巢是由结合到归巢片段的多个蛋白与结合到 engrailed/invected 染色质域的多个区域的蛋白之间的相互作用介导的。染色质结构也可能在归巢中发挥作用。
