Corepressive Action of CBP on Androgen Receptor Transactivation in Pericentric Heterochromatin in a Drosophila Experimental Model System
Corepressive Action of CBP on Androgen Receptor Transactivation in Pericentric Heterochromatin in a Drosophila Experimental Model System
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DOI：
10.1128/mcb.02123-07
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发表时间：
2008-12
影响因子：
5.3
通讯作者：
Yue Zhao;K. Takeyama;S. Sawatsubashi;Saya Ito;E. Suzuki;K. Yamagata;Masahiko Tanabe;Shuhei Kimura
中科院分区：
文献类型：
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作者：
Yue Zhao;K. Takeyama;S. Sawatsubashi;Saya Ito;E. Suzuki;K. Yamagata;Masahiko Tanabe;Shuhei Kimura
摘要 配体结合核受体 (NR) 激活靶基因的转录。这种激活通过各种核心调节因子的功能与组蛋白修饰和染色质重塑相结合。然而，NR 共调节因子作用对靶基因染色质环境存在依赖性的性质尚不清楚。为了解决这个问题，我们开发了一种改良的位置效应杂色实验模型系统，其中包括插入果蝇染色体中心周异染色质区域或常染色质区域的雄激素依赖性报告基因转基因。人雄激素受体（AR）及其组成型活性截短突变体（AR AF-1）在两个染色体区域均具有转录功能。可以预见的是，AR 诱导的反式激活水平在中心周异染色质中较低。在 AR AF-1 共调节子的遗传筛选中，发现果蝇 CREB 结合蛋白 (dCBP) 在中心周区域共抑制 AR 反式激活，而导致常染色质区域共激活。 Sir2 乙酰化位点的突变或 CBP 乙酰转移酶结构域的缺失消除了体内异染色质区域 dCBP 对 AR 的共抑制作用。在培养的哺乳动物细胞中，在 AR 靶基因的转录沉默启动子中观察到了 AR 的这种 CBP 辅阻遏物功能。因此，我们的研究结果表明 NR 共调节子的作用可能取决于目标位点染色质的状态。
ABSTRACT Ligand-bound nuclear receptors (NR) activate transcription of the target genes. This activation is coupled with histone modifications and chromatin remodeling through the function of various coregulators. However, the nature of the dependence of a NR coregulator action on the presence of the chromatin environment at the target genes is unclear. To address this issue, we have developed a modified position effect variegation experimental model system that includes an androgen-dependent reporter transgene inserted into either a pericentric heterochromatin region or a euchromatic region of Drosophila chromosome. Human androgen receptor (AR) and its constitutively active truncation mutant (AR AF-1) were transcriptionally functional in both chromosomal regions. Predictably, the level of AR-induced transactivation was lower in the pericentric heterochromatin. In genetic screening for AR AF-1 coregulators, Drosophila CREB binding protein (dCBP) was found to corepress AR transactivation at the pericentric region whereas it led to coactivation in the euchromatic area. Mutations of Sir2 acetylation sites or deletion of the CBP acetyltransferase domain abrogated dCBP corepressive action for AR at heterochromatic areas in vivo. Such a CBP corepressor function for AR was observed in the transcriptionally silent promoter of an AR target gene in cultured mammalian cells. Thus, our findings suggest that the action of NR coregulators may depend on the state of chromatin at the target loci.