Meraner Joachim, Lechner Markus, Loidl Adele, Goralik-Schramel Maria, Voit Renate, Grummt Ingrid, Loidl Peter
Division of Molecular Biology, Biocenter, Innsbruck Medical University, A-6020 Innsbruck, Austria.
Nucleic Acids Res. 2006 Mar 31;34(6):1798-806. doi: 10.1093/nar/gkl101. Print 2006.
The upstream binding factor UBF, an activator of RNA polymerase I transcription, is posttranslationally modified by phosphorylation and acetylation. We found that in NIH3T3 cells, UBF is acetylated in S-phase but not in G1-phase. To assess the role of acetylation in regulation of UBF activity, we have established an NIH3T3 cell line that inducibly overexpresses HDAC1. Both in vivo and in vitro, HDAC1 efficiently hypoacetylates UBF. Immunoprecipitation with antibodies against the Pol I-associated factor PAF53 co-precipitated UBF in mock cells but not in cells overexpressing HDAC1. Pull-down experiments showed that acetylation of UBF augments the interaction with Pol I. Consistent with acetylation of UBF being important for association of PAF53 and recruitment of Pol I, the level of Pol I associated with rDNA and pre-rRNA synthesis were reduced in cells overexpressing HDAC1. The results suggest that acetylation and deacetylation of UBF regulate rRNA synthesis during cell cycle progression.
上游结合因子UBF是RNA聚合酶I转录的激活因子，会通过磷酸化和乙酰化进行翻译后修饰。我们发现，在NIH3T3细胞中，UBF在S期被乙酰化，而在G1期则未被乙酰化。为了评估乙酰化在调节UBF活性中的作用，我们建立了一种可诱导过表达HDAC1的NIH3T3细胞系。在体内和体外，HDAC1均能有效地使UBF去乙酰化。用针对与Pol I相关因子PAF53的抗体进行免疫沉淀，在对照细胞中能共沉淀出UBF，但在过表达HDAC1的细胞中则不能。下拉实验表明，UBF的乙酰化增强了其与Pol I的相互作用。与UBF的乙酰化对PAF53的结合和Pol I的募集很重要一致，在过表达HDAC1的细胞中，与rDNA相关的Pol I水平以及前体rRNA的合成均降低。结果表明，UBF的乙酰化和去乙酰化在细胞周期进程中调节rRNA的合成。
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