Ishida Chisaki, Ura Kiyoe, Hirao Akiko, Sasaki Hiroyuki, Toyoda Atsushi, Sakaki Yoshiyuki, Niwa Hitoshi, Li En, Kaneda Yasufumi
Division of Gene Therapy Science, Osaka University School of Medicine, 2-2 Yamada-oka, Suita, 565-0870, Osaka, Japan.
Gene. 2003 May 22;310:151-9. doi: 10.1016/s0378-1119(03)00545-6.
The Dnmt3b gene encodes a de novo DNA methyltransferase that is essential for normal mouse development. It is highly expressed in early embryos and embryonic stem (ES) cells but downregulated in most adult somatic tissues. To gain insight into the regulation of Dnmt3b, we have isolated a mouse genomic bacterial artificial chromosome clone that contains the Dnmt3b gene. Complete sequence analysis of the clone demonstrated that Dnmt3b consists of at least 24 exons and spans 38 kilobases. S1 nuclease analysis identified two adjacent transcriptional start sites located downstream of a unique TATA-like element in a CpG island. There was an unknown gene which we named mU(3) 17 kb upstream of the Dnmt3b locus, and it was transcribed ubiquitously and in the opposite direction of Dnmt3b. Transfection analysis revealed that the minimal promoter region containing an Sp1 site was active even in somatic cells, and that there were several repressor elements within 7.9 kb upstream of Dnmt3b downregulated this gene specifically in somatic cells but not in ES cells. These findings provide a basis for future detailed studies of the mechanisms controlling Dnmt3b expression.
Dnmt3b基因编码一种从头DNA甲基转移酶，对正常小鼠发育至关重要。它在早期胚胎和胚胎干细胞（ES细胞）中高度表达，但在大多数成体体细胞组织中表达下调。为深入了解Dnmt3b的调控机制，我们分离出了一个包含Dnmt3b基因的小鼠基因组细菌人工染色体克隆。对该克隆的完整序列分析表明，Dnmt3b至少由24个外显子组成，跨度为38千碱基。S1核酸酶分析确定了两个相邻的转录起始位点，位于一个CpG岛中一个独特的类TATA元件下游。在Dnmt3b基因座上游17 kb处有一个未知基因，我们将其命名为mU(3)，它在各个组织中均有转录，且转录方向与Dnmt3b相反。转染分析表明，包含一个Sp1位点的最小启动子区域即使在体细胞中也具有活性，并且在Dnmt3b上游7.9 kb范围内有几个抑制元件，这些元件在体细胞中特异性下调该基因的表达，但在ES细胞中则不然。这些发现为未来详细研究控制Dnmt3b表达的机制提供了基础。
