Suppression of tyrosinase gene expression by bromodeoxyuridine in Syrian hamster melanoma cells is not due to its incorporation into upstream or coding sequences of the tyrosinase gene.
Suppression of tyrosinase gene expression by bromodeoxyuridine in Syrian hamster melanoma cells is not due to its incorporation into upstream or coding sequences of the tyrosinase gene.
复制标题
叙利亚仓鼠黑色素瘤细胞中溴脱氧尿苷对酪氨酸酶基因表达的抑制并不是由于其掺入酪氨酸酶基因的上游或编码序列。
DOI：
10.1007/bf01233076
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Davidson,RL
中科院分区：
文献类型：
--
作者：
Rauth,S;Davidson,RL
5-Bromodeoxyuridine (BrdU) 是一种胸苷类似物，可抑制叙利亚仓鼠黑色素瘤细胞中的黑色素生成。酪氨酸酶是合成黑色素的关键酶，接触 BrdU 会受到抑制，酶活性的下降与酪氨酸酶 mRNA 水平的下降相关。为了研究 BrdU 对酪氨酸酶 mRNA 的抑制是否是由于 BrdU 替换为酪氨酸酶基因的编码序列或上游序列，我们使用包含受非酪氨酸酶启动子控制的人酪氨酸酶 cDNA 序列或受小鼠酪氨酸酶基因 5' 侧翼序列控制的氯霉素乙酰转移酶 (CAT) 报告基因的构建体进行了稳定和瞬时转染测定。当含有酪氨酸酶cDNA的质粒稳定转染到小鼠成纤维细胞中时，转染子中的酪氨酸酶活性没有被BrdU抑制。由于 BrdU 将掺入到这些转染子中整合的酪氨酸酶 cDNA 中，因此结果表明，BrdU 对酪氨酸酶基因表达的抑制并不是由于其掺入到酪氨酸酶基因的编码序列中。当将带有酪氨酸酶调节序列的质粒转染入黑色素瘤细胞进行瞬时表达测定时，CAT 基因表达被 BrdU 抑制。由于 CAT 质粒不包含哺乳动物复制起点，并且不应在瞬时转染条件下复制，因此 BrdU 不会掺入这些质粒的 DNA 中。因此，这些结果表明BrdU对酪氨酸酶基因表达的抑制也不是由于BrdU掺入酪氨酸酶基因的上游序列所致。
5-Bromodeoxyuridine (BrdU), a thymidine analog, suppresses melanogenesis in Syrian hamster melanoma cells. Tyrosinase, which is the key enzyme for the synthesis of melanin, is suppressed by exposure to BrdU, and the drop in enzyme activity is correlated with a drop in tyrosinase mRNA level. In order to investigate whether suppression of tyrosinase mRNA by BrdU is due to BrdU substitution into coding sequences or upstream sequences of the tyrosinase gene, we carried out stable and transient transfection assays with constructs containing either the human tyrosinase cDNA sequence under the control of a nontyrosinase promoter or a chloramphenicol acetyltransferase (CAT) reporter gene under the control of 5′ flanking sequences of the mouse tyrosinase gene. When the plasmid containing the tyrosinase cDNA was stably transfected into mouse fibroblasts, tyrosinase activity in the transfectants was not suppressed by BrdU. Since BrdU would be incorporated into the tyrosinase cDNA integrated in these transfectants, the results suggest that BrdU suppression of tyrosinase gene expression is not due to its incorporation into coding sequences of the tyrosinase gene. When plasmids with tyrosinase regulatory sequences were transfected into melanoma cells for transient expression assays, CAT gene expression was suppressed by BrdU. Because the CAT plasmids do not contain a mammalian origin of replication and should not replicate under the conditions of transient transfection, BrdU would not be incorporated into the DNA of those plasmids. Therefore, these results suggest that the suppression of tyrosinase gene expression by BrdU also is not due to the incorporation of BrdU into upstream sequences of the tyrosinase gene.