MITHRAMYCIN INHIBITS SP1 BINDING AND SELECTIVELY INHIBITS TRANSCRIPTIONAL ACTIVITY OF THE DIHYDROFOLATE-REDUCTASE GENE INVITRO AND INVIVO
MITHRAMYCIN INHIBITS SP1 BINDING AND SELECTIVELY INHIBITS TRANSCRIPTIONAL ACTIVITY OF THE DIHYDROFOLATE-REDUCTASE GENE INVITRO AND INVIVO
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DOI：
10.1172/jci115474
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发表时间：
1991-11-01
影响因子：
15.9
通讯作者：
MILLER, DM
中科院分区：
文献类型：
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作者：
BLUME, SW;SNYDER, RC;MILLER, DM
人二氢叶酸还原酶（DHFR）基因的启动子含有DNA结合蛋白Sp1的两个一致的结合位点。dna酶保护和凝胶迁移转移实验表明重组Sp1与位于转录起始位点上游49和14个碱基对的十核核苷酸Sp1结合序列结合。两个结合位点中较远的位点对Sp1具有较高的亲和力。G-C特异性DNA结合药物，米霉素，结合到两个共识序列并阻止随后的Sp1结合。与人类H2b组蛋白基因相比，米霉素选择性地抑制DHFR模板启动子依赖性的体外转录。在体内也发现了类似的效果。米霉素处理含有扩增DHFR基因的MCF-7人乳腺癌细胞诱导DHFR转录起始选择性抑制，导致DHFR mRNA水平和酶活性下降。这种对DHFR表达的选择性抑制表明，在甲氨蝶呤耐药细胞中，有可能调节DHFR基因的过表达。
The promoter of the human dihydrofolate reductase (DHFR) gene contains two consensus binding sites for the DNA binding protein Sp1. DNAse protection and gel mobility shift assays demonstrate binding of recombinant Sp1 to both decanucleotide Sp1 binding sequences which are located 49 and 14 base pairs upstream of the transcription start site. The more distal of the two binding sites exhibits a somewhat higher affinity for Sp1. The G-C specific DNA binding drug, mithramycin, binds to both consensus sequences and prevents subsequent Sp1 binding. Promoter-dependent in vitro transcription of a DHFR template is selectively inhibited by mithramycin when compared to the human H2b histone gene. A similar effect is also noted in vivo. Mithramycin treatment of MCF-7 human breast carcinoma cells containing an amplified DHFR gene induces selective inhibition of DHFR transcription initiation, resulting in a decline in DHFR mRNA level and enzyme activity. This selective inhibition of DHFR expression suggests that it is possible to modulate the overexpression of the DHFR gene in methotrexate resistant cells.