Joyeux C, Rochefort H, Chalbos D
Unité Hormones et Cancer, INSERM U 148--UAC 59 CNRS, Montpellier, France.
Mol Endocrinol. 1989 Apr;3(4):681-6. doi: 10.1210/mend-3-4-681.
The cDNA clone (Pg8) corresponding to the 3'-end of fatty acid synthetase (FAS) mRNA is one of the few probes to study in cell lines the mechanism by which an endogenous gene is regulated by progestins. The steady-state level of FAS mRNA is known to be increased by the synthetic progestin R5020 in the human breast cancer cell line MCF7. We show here that it is also increased in another progesterone-receptor-positive cell line T47D but not in progesterone-receptor-negative cell lines BT20, MDA-MB231, and HBL100. In R5020-treated MCF7 cells, the FAS mRNA concentration increased with cell density. Protein synthesis inhibitors did not abolish progestin induction of FAS suggesting a primary effect of the hormone. In vitro nuclear run-on transcription assays showed that the FAS gene transcription rate was increased about 4-fold by progestin. This stimulation of transcription was detectable 30 min after addition of R5020 and was maximal after 4 h, but could not totally account for the total increase in the mRNA steady state level. Chase experiments in the presence of Actinomycin D or Cordycepin showed that progestin also increased the half-life of FAS mRNA from 6-9 h to 24-33 h. We conclude that progestin stimulates the FAS concentration both by increasing the transcription rate of the gene and by stabilizing the mRNA.
与脂肪酸合成酶（FAS）mRNA 3'端相对应的cDNA克隆（Pg8），是用于在细胞系中研究内源性基因受孕激素调控机制的少数几种探针之一。已知在人乳腺癌细胞系MCF7中，合成孕激素R5020可提高FAS mRNA的稳态水平。我们在此表明，在另一种孕激素受体阳性细胞系T47D中其水平也会升高，但在孕激素受体阴性细胞系BT20、MDA-MB231和HBL100中则不会升高。在经R5020处理的MCF7细胞中，FAS mRNA浓度随细胞密度增加而升高。蛋白质合成抑制剂并不能消除孕激素对FAS的诱导作用，这表明该激素具有主要作用。体外细胞核连续转录分析表明，孕激素可使FAS基因转录速率提高约4倍。添加R5020后30分钟即可检测到这种转录刺激作用，4小时后达到最大值，但这并不能完全解释mRNA稳态水平的总体升高。在放线菌素D或虫草素存在的情况下进行的追踪实验表明，孕激素还可使FAS mRNA的半衰期从6 - 9小时延长至24 - 33小时。我们得出结论，孕激素通过提高基因转录速率和稳定mRNA来刺激FAS浓度。
