Bresnick E H, John S, Berard D S, LeFebvre P, Hager G L
Hormone Action and Oncogenesis Section, National Cancer Institute, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1990 May;87(10):3977-81. doi: 10.1073/pnas.87.10.3977.
Our laboratory has previously developed cell lines derived from mouse NIH 3T3 fibroblasts and C127 mammary tumor cells that stably express mouse mammary tumor virus (MMTV) long terminal repeat fusion genes in bovine papillomavirus-based episomes. Glucocorticoid hormone strongly activates transcription from episomes and induces the disruption of a single nucleosome in an array of phased nucleosomes on the MMTV promoter. Sodium butyrate inhibits the glucocorticoid hormone-dependent development of a nuclease-hypersensitive site that is due to the displacement of this nucleosome, and inhibits induction of RNA transcripts from episomes. Saturation binding studies show that butyrate treatment does not significantly affect the amount or the hormone-binding affinity of the glucocorticoid receptor. In a transient transfection assay, glucocorticoid hormone can activate transcription from a MMTV long terminal repeat-driven luciferase gene construct equivalently in untreated and butyrate-treated cells, indicating that the soluble factors necessary for transactivation of the MMTV promoter are unaffected by butyrate. The differential effect of butyrate on the induction of stable chromatin templates and transiently expressed plasmids suggests that butyrate prevents nucleosome displacement and represses transcription by inducing a modification of chromatin.
我们实验室之前已从源自小鼠NIH 3T3成纤维细胞和C127乳腺肿瘤细胞的细胞系中培养出细胞系，这些细胞系在基于牛乳头瘤病毒的附加体中稳定表达小鼠乳腺肿瘤病毒（MMTV）长末端重复融合基因。糖皮质激素能强烈激活附加体的转录，并诱导MMTV启动子上一系列有序核小体中的单个核小体发生破坏。丁酸钠抑制因该核小体移位而导致的核酸酶超敏位点的糖皮质激素依赖性发育，并抑制附加体RNA转录本的诱导。饱和结合研究表明，丁酸钠处理不会显著影响糖皮质激素受体的量或激素结合亲和力。在瞬时转染试验中，糖皮质激素在未处理和丁酸钠处理的细胞中均能等效激活由MMTV长末端重复驱动的荧光素酶基因构建体的转录，这表明MMTV启动子反式激活所需的可溶性因子不受丁酸钠影响。丁酸钠对稳定染色质模板和瞬时表达质粒诱导的不同作用表明，丁酸钠通过诱导染色质修饰来阻止核小体移位并抑制转录。
