Ponnazhagan S, Kwon B S
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis 46202.
Pigment Cell Res. 1992 Oct;5(4):155-61. doi: 10.1111/j.1600-0749.1992.tb00453.x.
The tyrosinase gene is specifically expressed in melanocytes. Understanding the molecular basis of tissue-specific expression of the tyrosinase gene will greatly explain the mechanisms controlling pigmentation. We report a nucleotide sequence, TGATGTATTC, located -236 base pairs upstream of the transcription start site, that enhances tyrosinase gene expression in mouse melanoma cells. The sequence is referred to as the tyrosinase element-1 (TE-1). TE-1 was protected from DNase I cleavage by pigment cell nuclear extracts but was not protected by non-pigment cell nuclear extract. Partial purification of TE-1 binding protein (TEBP-1) was performed from the B16 mouse melanoma cell nuclear extract using biotin-cellulose affinity chromatography. The affinity-purified fraction exhibited binding to the DNA fragment containing TE-1, and to a synthetic oligomer representing TE-1. UV-cross-linking indicated that the size of TEBP-1 is approximately 49 kD. TE-1 also directed enhanced CAT activity in the B16 melanoma cells but not in non-pigment cells. These data indicate that TE-1 may be an enhancer element that is responsible for pigment cell specific expression of the tyrosinase gene.
酪氨酸酶基因在黑素细胞中特异性表达。了解酪氨酸酶基因组织特异性表达的分子基础将极大地解释控制色素沉着的机制。我们报道了一个位于转录起始位点上游-236个碱基对处的核苷酸序列TGATGTATTC，它能增强小鼠黑素瘤细胞中酪氨酸酶基因的表达。该序列被称为酪氨酸酶元件-1（TE-1）。TE-1能被色素细胞核提取物保护不被DNase I切割，但不能被非色素细胞核提取物保护。使用生物素-纤维素亲和色谱法从B16小鼠黑素瘤细胞核提取物中对TE-1结合蛋白（TEBP-1）进行了部分纯化。亲和纯化的组分显示出与含有TE-1的DNA片段以及代表TE-1的合成寡聚物结合。紫外线交联表明TEBP-1的大小约为49 kD。TE-1也能在B16黑素瘤细胞中而非非色素细胞中指导增强的氯霉素乙酰转移酶（CAT）活性。这些数据表明TE-1可能是一个增强子元件，负责酪氨酸酶基因在色素细胞中的特异性表达。
