Sacca R, Cochran B H
Massachusetts Institute of Technology, Center for Cancer Research, Cambridge 02139.
Oncogene. 1990 Oct;5(10):1499-505.
The c-myc gene is rapidly induced in quiescent Balb/c-3T3 cells in response to the platelet-derived growth factor (PDGF). In order to study the mechanisms by which growth factors regulate induction of c-myc, we have attempted to identify growth factor-responsive elements in the murine c-myc locus. Various fragments of the c-myc gene linked to a bacterial CAT reporter gene were stably transfected into Balb/c-3T3 cells. A construct which includes the P1 promoter and 424 bp of upstream sequences shows a 3-5 fold induction of CAT RNA expression in response to sis/PDGF. S1 nuclease mapping experiments demonstrate that this mRNA initiates from the myc P1 promoter. Nuclear runoff transcription experiments performed with this myc/CAT construct show that this induction occurs at the transcriptional level. Deletion analysis led to the identification of an 81 bp segment in the first exon between the c-myc P1 and P2 promoters which is necessary to confer growth factor responsiveness in this construct.
c-myc基因在静止的Balb/c-3T3细胞中会因血小板衍生生长因子（PDGF）而迅速被诱导。为了研究生长因子调节c-myc基因诱导的机制，我们试图在小鼠c-myc基因座中鉴定生长因子反应元件。将与细菌氯霉素乙酰转移酶（CAT）报告基因相连的c-myc基因的各种片段稳定转染到Balb/c-3T3细胞中。一个包含P1启动子和424 bp上游序列的构建体在响应sis/PDGF时，CAT RNA表达有3至5倍的诱导。S1核酸酶图谱实验表明，这种mRNA从myc P1启动子起始。用这个myc/CAT构建体进行的核转录延伸实验表明，这种诱导发生在转录水平。缺失分析导致在c-myc P1和P2启动子之间的第一个外显子中鉴定出一个81 bp的片段，该片段对于赋予该构建体生长因子反应性是必需的。
