Tanimoto K, Eguchi H, Yoshida T, Hajiro-Nakanishi K, Hayashi S
Hormone-Associated Cancer Research Group, Saitama Cancer Center Research Institute, Komuro, Ina-machi, Kitaadachi-gun, Saitama 362-0806, Japan.
Nucleic Acids Res. 1999 Feb 1;27(3):903-9. doi: 10.1093/nar/27.3.903.
We have previously reported that transcription from a distal promoter (promoter B) of the estrogen receptor alpha (ERalpha) gene is responsible for the increased expression of ERalpha in human breast carcinomas. This paper first characterized the promoter B region in terms of transient transfection experiments with luciferase using MCF-7 cells. Gradual deletions from the 5'-end of promoter B resulted in a decrease in promoter activity corresponding to the deleted lengths; a deletion of 39 bp in a non-coding exon 1a, drastically diminished the activity, indicating existence of an important cis -element. Furthermore, electrophoretic mobility shift assay and subsequent mutational analysis indicated that this element containing nucleotide sequence CTGGAAAG forms a specific DNA-protein complex. This element was capable of transactivating a heterogeneous SV40 promoter in MCF-7 cells, confirming that the element is a transcriptional enhancer; the trans -acting factor binding to the element was named ERBF-1 (estrogen receptor promoter B associated factor-1). The ERBF-1 was exclusively expressed in those cells expressing ERalpha mRNA transcribed from promoter B. Our findings indicate that ERBF-1 plays an important role in the expression of the ERalpha gene transcribed from promoter B, which is selectively utilized in breast cancer.
我们之前报道过，雌激素受体α（ERα）基因远端启动子（启动子B）的转录负责人类乳腺癌中ERα表达的增加。本文首先通过使用MCF-7细胞进行荧光素酶瞬时转染实验，对启动子B区域进行了表征。从启动子B的5'端逐渐缺失导致启动子活性随缺失长度而降低；非编码外显子1a中39 bp的缺失显著降低了活性，表明存在一个重要的顺式元件。此外，电泳迁移率变动分析及随后的突变分析表明，这个包含核苷酸序列CTGGAAAG的元件形成了一个特定的DNA-蛋白质复合物。该元件能够在MCF-7细胞中转录激活异源的SV40启动子，证实该元件是一个转录增强子；与该元件结合的反式作用因子被命名为ERBF-1（雌激素受体启动子B相关因子-1）。ERBF-1仅在那些表达从启动子B转录而来的ERα mRNA的细胞中表达。我们的研究结果表明，ERBF-1在从启动子B转录的ERα基因的表达中起重要作用，而启动子B在乳腺癌中被选择性利用。
