Zhou J, Ashe H, Burks C, Levine M
Dept Mol. Cell Biol., Division of Genetics, University of California, Berkeley, CA 94720, USA.
Development. 1999 Jun;126(14):3057-65. doi: 10.1242/dev.126.14.3057.
Genetic studies have identified an unusual transvection process in the Abdominal-B (Abd-B) locus of Drosophila. In some cases distal infraabdominal (iab) regulatory domains continue to activate the Abd-B promoter even when translocated onto different chromosomes. Transvection depends on an approx. 10 kb genomic DNA sequence, termed the transvection mediating region (tmr), located immediately downstream of the Abd-B transcription unit. Here we report a detailed analysis of this region. Different DNA fragments from the tmr were inserted into a variety of P-transformation vectors. Analyses of reporter gene expression in transgenic embryos and adults identify at least three cis-regulatory elements, including two enhancers (IAB7 and IAB8) and a new insulator DNA (Frontabdominal-8, Fab-8). Evidence is also presented for a Polycomb Response Element (PRE) linked to the IAB8 enhancer, and an internal promoter in the iab-8 domain, which transcribes the iab-7 and iab-8 cis-regulatory DNA, including the Fab-8 insulator. We discuss the significance of these findings with regard to Abd-B transvection and long-range enhancer-promoter interactions in mammalian globin loci.
遗传学研究在果蝇的腹部B（Abd - B）基因座中发现了一种不同寻常的异位效应过程。在某些情况下，即使远端腹下（iab）调控结构域被转移到不同染色体上，它们仍能继续激活Abd - B启动子。异位效应依赖于一个约10 kb的基因组DNA序列，称为异位效应介导区域（tmr），它位于Abd - B转录单元的紧下游。在此，我们报告对该区域的详细分析。来自tmr的不同DNA片段被插入到多种P转导载体中。对转基因胚胎和成虫中报告基因表达的分析确定了至少三个顺式调控元件，包括两个增强子（IAB7和IAB8）和一个新的绝缘子DNA（前腹8，Fab - 8）。还提供了与IAB8增强子相连的多梳反应元件（PRE）以及iab - 8结构域中的一个内部启动子的证据，该启动子转录iab - 7和iab - 8顺式调控DNA，包括Fab - 8绝缘子。我们讨论了这些发现对于Abd - B异位效应以及哺乳动物珠蛋白基因座中远程增强子 - 启动子相互作用的意义。
