Meraner Joachim, Lechner Markus, Schwarze Florian, Gander Roland, Jesacher Florian, Loidl Peter
Innsbruck-Biocenter, Division of Molecular Biology, Innsbruck Medical University, Fritz-Pregl-Strasse 3, A-6020 Innsbruck, Austria.
Cell Biol Int. 2008 Sep;32(9):1073-80. doi: 10.1016/j.cellbi.2008.04.018. Epub 2008 May 2.
Ribosome biogenesis and ribosomal DNA transcription are closely correlated with the growth and proliferation of cells, with these processes being under tight epigenetic control. We have investigated the effect of ectopically expressed murine HDAC1 in reporter assays, on ribosomal DNA transcription, cell cycle progression and proliferation in transfected mammalian cells. Ectopically expressed mHDAC1 represses transcription in ribosomal reporter assays driven by ribosomal promoter elements in NIH3T3 cells as well as Cos-7 cells. Following stable transfection of NIH3T3 cells, flag-tagged HDAC1 is assembled into functional, enzymatically active HDAC-complexes that display correct nuclear localization. Induction of flag-HDAC1 expression in NIH3T3 cells caused a cell-cycle phase specific reduction in the initiation of endogenous rDNA transcription, reflected in a reduction of nascent rRNA as well as a marked depression of proliferation due to prolongation of G2-phase. This was substantiated by FACS analysis and cyclin B1 expression analysis. However, prolongation of the G2-phase in HDAC1-overexpressing cells finally led to overcompensation and thus to an increase in total ribosomal RNA. The transient downregulation of rRNA synthesis after induction of HDAC1 overexpression led to a prolongation of G2-phase. These observations were most likely a consequence of HDAC1-mediated deacetylation of upstream binding factor (UBF).
核糖体生物合成和核糖体DNA转录与细胞的生长和增殖密切相关，这些过程受到严格的表观遗传控制。我们在报告基因检测中研究了异位表达的小鼠HDAC1对转染的哺乳动物细胞中核糖体DNA转录、细胞周期进程和增殖的影响。异位表达的mHDAC1在由NIH3T3细胞和Cos-7细胞中的核糖体启动子元件驱动的核糖体报告基因检测中抑制转录。在NIH3T3细胞稳定转染后，带有flag标签的HDAC1组装成具有功能的、酶活性的HDAC复合物，显示出正确的核定位。在NIH3T3细胞中诱导flag-HDAC1表达导致内源性rDNA转录起始的细胞周期阶段特异性减少，表现为新生rRNA减少以及由于G2期延长导致的增殖显著抑制。这通过FACS分析和细胞周期蛋白B1表达分析得到证实。然而，HDAC1过表达细胞中G2期的延长最终导致过度补偿，从而导致总核糖体RNA增加。HDAC1过表达诱导后rRNA合成的短暂下调导致G2期延长。这些观察结果很可能是HDAC1介导的上游结合因子（UBF）去乙酰化的结果。
