Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
PLoS One. 2012;7(3):e31484. doi: 10.1371/journal.pone.0031484. Epub 2012 Mar 1.
The Scl gene encodes a transcription factor essential for haematopoietic development. Scl transcription is regulated by a panel of cis-elements spread over 55 kb with the most distal 3' element being located downstream of the neighbouring gene Map17, which is co-regulated with Scl in haematopoietic cells. The Scl/Map17 domain is flanked upstream by the ubiquitously expressed Sil gene and downstream by a cluster of Cyp genes active in liver, but the mechanisms responsible for delineating the domain boundaries remain unclear. Here we report identification of a DNaseI hypersensitive site at the 3' end of the Scl/Map17 domain and 45 kb downstream of the Scl transcription start site. This element is located at the boundary of active and inactive chromatin, does not function as a classical tissue-specific enhancer, binds CTCF and is both necessary and sufficient for insulator function in haematopoietic cells in vitro. Moreover, in a transgenic reporter assay, tissue-specific expression of the Scl promoter in brain was increased by incorporation of 350 bp flanking fragments from the +45 element. Our data suggests that the +45 region functions as a boundary element that separates the Scl/Map17 and Cyp transcriptional domains, and raise the possibility that this element may be useful for improving tissue-specific expression of transgenic constructs.
Scl 基因编码一种对造血发育至关重要的转录因子。Scl 转录受一组顺式元件调控，这些元件分布在 55kb 以上，最远端的 3' 元件位于邻近基因 Map17 的下游，Map17 在造血细胞中与 Scl 共同调控。Scl/Map17 结构域的上游由广泛表达的 Sil 基因侧翼，下游由一组在肝脏中活跃的 Cyp 基因簇侧翼，但负责划定结构域边界的机制仍不清楚。在这里，我们报道了在 Scl/Map17 结构域的 3' 末端和 Scl 转录起始位点下游 45kb 处鉴定到一个 DNaseI 超敏位点。该元件位于活性和非活性染色质的边界处，不作为经典的组织特异性增强子发挥作用，与 CTCF 结合，并且在体外造血细胞中具有绝缘子功能所必需且充分。此外，在转基因报告基因检测中，通过整合来自+45 元件的 350bp 侧翼片段，脑内 Scl 启动子的组织特异性表达增加。我们的数据表明，+45 区域作为一个边界元件，分隔 Scl/Map17 和 Cyp 转录结构域，并提出了这样一种可能性，即该元件可能有助于提高转基因构建体的组织特异性表达。
