Evett G E, Xie W, Chipman J G, Robertson D L, Simmons D L
Department of Chemistry, Brigham Young University, Provo, Utah 84602.
Arch Biochem Biophys. 1993 Oct;306(1):169-77. doi: 10.1006/abbi.1993.1496.
Mitogens increase prostaglandin synthesis in fibroblasts. In the present studies, transcriptional activation of the prostaglandin G/H synthase isoenzyme 2 (PGHS-2) gene is shown to be responsible for this induction. Transcription of the PGHS-2 gene maximally increased within 15 min of stimulation, and elevated cellular PGHS-2 mRNA, protein, and prostaglandin synthase activity were detected shortly thereafter. Pulse-chase experiments showed induced isoenzyme 2 is short lived, with a half-life of 22 min in chicken embryo fibroblasts. Neoplastic transformation of fibroblasts by a variety of oncogenes induced either or both PGHS-1 and PGHS-2 mRNAs in immortalized murine NIH3T3 cells. Some preference of oncogenes such as v-src to induce PGHS-2 mRNA has been previously observed. However, in this study exceptions in which v-src did not induce PGHS-2 mRNA were noted. Analysis of independent cell lines transformed by v-fes showed this oncogene induced both PGHS-1 and PGHS-2. Dexamethasone, a synthetic glucocorticoid, selectively decreased both basal and induced levels of PGHS-2 mRNA. Simultaneous addition of the steroid with mitogen reduced mitogen-induced PGHS-2 mRNA levels by 80%. However, nuclear run-on experiments failed to detect any decrease in PGHS-2 mRNA transcription. This suggested dexamethasone rapidly caused PGHS-2 mRNA destabilization. Cycloheximide blocked PGHS-2 mRNA decrease. A fibroblast cell line, RS2, was identified that contained only isoenzyme 2 and possessed PGHS activity that was more highly mitogen-inducible than in any other cell line yet described. Mitogen-inducible activity in RS2 cells was inhibited by aspirin, indicating that PGHS-2, like PGHS-1, can be inactivated by this drug.
有丝分裂原可增加成纤维细胞中前列腺素的合成。在本研究中，前列腺素G/H合酶同工酶2（PGHS-2）基因的转录激活被证明是这种诱导作用的原因。PGHS-2基因的转录在刺激后15分钟内最大程度增加，随后不久检测到细胞内PGHS-2 mRNA、蛋白质和前列腺素合酶活性升高。脉冲追踪实验表明，诱导产生的同工酶2寿命较短，在鸡胚成纤维细胞中的半衰期为22分钟。多种癌基因使成纤维细胞发生肿瘤转化，可在永生化的小鼠NIH3T3细胞中诱导产生PGHS-1和PGHS-2 mRNA中的一种或两种。先前已观察到某些癌基因（如v-src）更倾向于诱导PGHS-2 mRNA。然而，在本研究中注意到有v-src不诱导PGHS-2 mRNA的例外情况。对由v-fes转化的独立细胞系的分析表明，这种癌基因可诱导PGHS-1和PGHS-2。合成糖皮质激素地塞米松选择性降低PGHS-2 mRNA的基础水平和诱导水平。将该类固醇与有丝分裂原同时添加可使有丝分裂原诱导的PGHS-2 mRNA水平降低80%。然而，细胞核连续转录实验未能检测到PGHS-2 mRNA转录有任何降低。这表明地塞米松迅速导致PGHS-2 mRNA不稳定。放线菌酮可阻止PGHS-2 mRNA的降低。鉴定出一种成纤维细胞系RS2，其仅含有同工酶2，并且具有比迄今描述的任何其他细胞系更高的有丝分裂原诱导性PGHS活性。RS2细胞中的有丝分裂原诱导活性被阿司匹林抑制，表明PGHS-2与PGHS-1一样，可被该药物灭活。
