Kitabayashi I, Kawakami Z, Matsuoka T, Chiu R, Gachelin G, Yokoyama K
Tsukuba Life Science Center, RIKEN (the Institute of Physical and Chemical Research), Ibaraki, Japan.
J Biol Chem. 1993 Jul 5;268(19):14482-9.
Transcription of the junB gene is rapidly and transiently induced by a variety of extracellular signals. We report here that expression directed by a junB promoter/chloramphenicol acetyltransferase reporter construct (junB/CAT) is induced by fetal bovine serum, 12-O-tetradecanoylphorbol-13-acetate (TPA), epidermal growth factor (EGF), platelet-derived growth factor, and fibroblast growth factor in mouse fibroblast 3T6 cells. Deletion analysis of the promoter region of the junB gene indicates that there are at least two cis-regulatory elements that confer the capacity for serum-dependent induction. These two serum response elements (SRE1 and SRE2) are mapped between nucleotides -1451 and -1425 and between nucleotides -3100 and -2500, respectively, relative to the site of initiation of transcription. SRE1, the nucleotide sequence of which resembles that of the serum response element of the c-fos gene, is activated by TPA, platelet-derived growth factor, and fibroblast growth factor, but these growth-stimulating factors do not induce SRE2-mediated transcription. Pretreatment of the cells with phorbol dibutyrate, which reduces the level of protein kinase C activity in cells, almost completely abolishes the activation of SRE1 by TPA. Pretreatment with phorbol dibutyrate also reduces (but does not eliminate) the serum-dependent activation of SRE1. By contrast, the induction of SRE2 by serum is not affected by this pretreatment. Herbimycin A, an inhibitor of protein kinases, inhibits the activity of SRE2, but not that of SRE1. These results suggest that transcription of the junB gene can be induced by at least two distinct signaling pathways, which are mediated by SRE1 and SRE2, respectively. In addition, EGF induces expression of junB/CAT as strongly as does serum, but neither SRE1 nor SRE2 is sufficient for responsiveness to EGF.
junB基因的转录可被多种细胞外信号迅速且短暂地诱导。我们在此报告，在小鼠成纤维细胞3T6中，由junB启动子/氯霉素乙酰转移酶报告构建体（junB/CAT）指导的表达可被胎牛血清、12-O-十四烷酰佛波醇-13-乙酸酯（TPA）、表皮生长因子（EGF）、血小板衍生生长因子和成纤维细胞生长因子诱导。对junB基因启动子区域的缺失分析表明，至少有两个顺式调节元件赋予了血清依赖性诱导能力。相对于转录起始位点，这两个血清反应元件（SRE1和SRE2）分别定位在核苷酸-1451至-1425之间以及核苷酸-3100至-2500之间。SRE1的核苷酸序列与c-fos基因的血清反应元件相似，可被TPA、血小板衍生生长因子和成纤维细胞生长因子激活，但这些生长刺激因子不会诱导SRE2介导的转录。用佛波醇二丁酸酯预处理细胞，可降低细胞中蛋白激酶C的活性，几乎完全消除TPA对SRE1的激活。用佛波醇二丁酸酯预处理也会降低（但不会消除）SRE1的血清依赖性激活。相比之下，血清对SRE2的诱导不受此预处理的影响。蛋白激酶抑制剂赫伯霉素A可抑制SRE2的活性，但不抑制SRE1的活性。这些结果表明，junB基因的转录可由至少两条不同的信号通路诱导，分别由SRE1和SRE2介导。此外，EGF诱导junB/CAT表达的强度与血清相同，但SRE1和SRE2均不足以介导对EGF的反应。
