Senawong Thanaset, Peterson Valerie J, Avram Dorina, Shepherd David M, Frye Roy A, Minucci Saverio, Leid Mark
Laboratory of Molecular Pharmacology, Department of Pharmaceutical Sciences, College of Pharmacy, Environmental Health Sciences Center, Oregon State University, Corvallis, Oregon 97331, USA.
J Biol Chem. 2003 Oct 31;278(44):43041-50. doi: 10.1074/jbc.M307477200. Epub 2003 Aug 19.
Chicken ovalbumin upstream promoter transcription factor (COUP-TF)-interacting proteins 1 and 2 (CTIP1 and CTIP2) enhance transcriptional repression mediated by COUP-TF II and have been implicated in hematopoietic cell development and malignancies. CTIP1 and CTIP2 are also sequence-specific DNA-binding proteins that repress transcription through direct, COUP-TF-in-dependent binding to a GC-rich response element. CTIP1- and CTIP2-mediated transcriptional repression is insensitive to trichostatin A, an inhibitor of known class I and II histone deacetylases. However, chromatin immunoprecipitation assays revealed that expression of CTIP2 in mammalian cells resulted in deacetylation of histones H3 and/or H4 that were associated with the promoter region of a reporter gene. CTIP2-mediated transcriptional repression, as well as deacetylation of promoter-associated histones H3/H4 in CTIP2-transfected cells, was reversed by nicotinamide, an inhibitor of class III histone deacetylases such as the mammalian homologs of yeast Silent Information Regulator 2 (Sir2). The human homolog of yeast Sir2, SIRT1, was found to interact directly with CTIP2 and was recruited to the promoter template in a CTIP2-dependent manner. Moreover, SIRT1 enhanced the deacetylation of template-associated histones H3/H4 in CTIP2-transfected cells, and stimulated CTIP2-dependent transcriptional repression. Finally, endogenous SIRT1 and CTIP2 co-purified from Jurkat cell nuclear extracts in the context of a large (1-2 mDa) complex. These findings implicate SIRT1 as a histone H3/H4 deacetylase in mammalian cells and in transcriptional repression mediated by CTIP2.
鸡卵清蛋白上游启动子转录因子（COUP-TF）相互作用蛋白1和2（CTIP1和CTIP2）增强了由COUP-TF II介导的转录抑制作用，并与造血细胞发育和恶性肿瘤有关。CTIP1和CTIP2也是序列特异性DNA结合蛋白，它们通过直接与富含GC的反应元件结合来抑制转录，这种结合不依赖于COUP-TF。CTIP1和CTIP2介导的转录抑制对曲古抑菌素A不敏感，曲古抑菌素A是已知的I类和II类组蛋白脱乙酰酶的抑制剂。然而，染色质免疫沉淀分析表明，CTIP2在哺乳动物细胞中的表达导致与报告基因启动子区域相关的组蛋白H3和/或H4去乙酰化。CTIP2介导的转录抑制以及CTIP2转染细胞中启动子相关组蛋白H3/H4的去乙酰化被烟酰胺逆转，烟酰胺是III类组蛋白脱乙酰酶的抑制剂，如酵母沉默信息调节因子2（Sir2）的哺乳动物同源物。发现酵母Sir2的人类同源物SIRT1直接与CTIP2相互作用，并以CTIP2依赖的方式被招募到启动子模板上。此外，SIRT1增强了CTIP2转染细胞中模板相关组蛋白H3/H4的去乙酰化，并刺激了CTIP2依赖的转录抑制。最后，内源性SIRT1和CTIP2在一个大的（1-2 mDa）复合物的背景下从Jurkat细胞核提取物中共纯化。这些发现表明SIRT1是哺乳动物细胞中的组蛋白H3/H4脱乙酰酶，并参与CTIP2介导的转录抑制。
