Transcriptional regulation of the human DNA methyltransferase 3A and 3B genes by Sp3 and Sp1 zinc finger proteins
Transcriptional regulation of the human DNA methyltransferase 3A and 3B genes by Sp3 and Sp1 zinc finger proteins
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DOI：
10.1042/bj20040684
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发表时间：
2005-01-15
影响因子：
4.1
通讯作者：
Yuasa, Y
中科院分区：
文献类型：
--
作者：
Jinawath, A;Miyake, S;Yuasa, Y
DNMT3A(DNA甲基转移酶3A)和DNMT3B基因编码可能的从头甲基转移酶，并分别在三个和两个不同启动子的存在下表现出复杂的转录调控。DNMT3A和DNMT3B的所有启动子都在其转录起始点附近缺乏典型的TATA序列，并含有几个Sp1结合位点。通过使用GC丰富的DNA结合蛋白抑制剂mithramycin A，即基于DNMT3a和Dnmt3b启动子活性和mRNA表达水平的降低，证明了这些Sp1结合位点的重要性。Sp1和Sp3的过表达上调了这两个基因的启动子活性。凝胶漂移实验证实Sp1和Sp3与DNMT3A和DNMT3B启动子有物理结合。有趣的是，在HEK-293T细胞(人胚胎肾293T细胞)中，SP3的过表达导致DNMT3a和Dnmt3b的mRNA表达水平分别增加了3.3倍和4.0倍，而Sp1的过表达却没有。此外，SP3的反义寡核苷酸显著降低了DNMT3a和Dnmt3b的mRNA水平。这些结果表明Sp蛋白，特别是Sp蛋白在调控DNMT3a和Dnmt3b基因表达方面具有重要的功能。
The DNMT3A (DNA methyltransferase 3A) and DNMT3B genes encode putative de novo methyltransferases and show complex transcriptional regulation in the presence of three and two different promoters respectively. All promoters of DNMT3A and DNMT3B lack typical TATA sequences adjacent to their transcription start sites and contain several Sp1-binding sites. The importance of these Sp1-binding sites was demonstrated by using a GC-rich DNA-binding protein inhibitor, mithramycin A, i.e. on the basis of decrease in the promoter activities and mRNA expression levels of DNMT3A and DNMT3B. Overexpression of Sp1 and Sp3 upregulated the promoter activities of these two genes. The physical binding of Sp1 and Sp3 to DNMT3A and DNMT3B promoters was confirmed by a gel shift assay. Interestingly, Sp3 overexpression in HEK-293T cells (human embryonic kidney 293T cells) resulted in 3.3- and 4.0-fold increase in DNMT3A and DNMT3B mRNA expression levels respectively by quantitative reverse transcriptasePCR, whereas Sp1 overexpression did not. Furthermore, an antisense oligonucleotide to Sp3 significantly decreased the mRNA levels of DNMT3A and DNMT3B. These results indicate the functional importance of Sp proteins, particularly Sp;, in the regulation of DNMT3A and DNMT3B gene expression.