Department of Plant Systems Biology, Flanders Institute for Biotechnology, 9052 Ghent, Belgium.
Proc Natl Acad Sci U S A. 2010 Jan 26;107(4):1678-83. doi: 10.1073/pnas.0913559107. Epub 2010 Jan 8.
In eukaryotes, transcription of protein-encoding genes is strongly regulated by posttranslational modifications of histones that affect the accessibility of the DNA by RNA polymerase II (RNAPII). The Elongator complex was originally identified in yeast as a histone acetyltransferase (HAT) complex that activates RNAPII-mediated transcription. In Arabidopsis thaliana, the Elongator mutants elo1, elo2, and elo3 with decreased leaf and primary root growth due to reduced cell proliferation identified homologs of components of the yeast Elongator complex, Elp4, Elp1, and Elp3, respectively. Here we show that the Elongator complex was purified from plant cell cultures as a six-component complex. The role of plant Elongator in transcription elongation was supported by colocalization of the HAT enzyme, ELO3, with euchromatin and the phosphorylated form of RNAPII, and reduced histone H3 lysine 14 acetylation at the coding region of the SHORT HYPOCOTYL 2 auxin repressor and the LAX2 auxin influx carrier gene with reduced expression levels in the elo3 mutant. Additional auxin-related genes were down-regulated in the transcriptome of elo mutants but not targeted by the Elongator HAT activity showing specificity in target gene selection. Biological relevance was apparent by auxin-related phenotypes and marker gene analysis. Ethylene and jasmonic acid signaling and abiotic stress responses were up-regulated in the elo transcriptome and might contribute to the pleiotropic elo phenotype. Thus, although the structure of Elongator and its substrate are conserved, target gene selection has diverged, showing that auxin signaling and influx are under chromatin control.
在真核生物中，蛋白质编码基因的转录受到组蛋白的翻译后修饰的强烈调节，这些修饰影响 RNA 聚合酶 II (RNAPII) 对 DNA 的可及性。Elongator 复合物最初在酵母中被鉴定为一种组蛋白乙酰转移酶 (HAT) 复合物，它可以激活 RNAPII 介导的转录。在拟南芥中，elo1、elo2 和 elo3 等 Elongator 突变体由于细胞增殖减少而导致叶片和主根生长不良，这些突变体鉴定出了酵母 Elongator 复合物的成分的同源物，分别为 Elp4、Elp1 和 Elp3。在这里，我们表明 Elongator 复合物可以从植物细胞培养物中作为一个六组分复合物进行纯化。植物 Elongator 在转录延伸中的作用得到了以下实验的支持：HAT 酶 ELO3 与常染色质和磷酸化形式的 RNAPII 共定位，并且在编码 SHORT HYPOCOTYL 2 生长素抑制剂和 LAX2 生长素流入载体基因的组蛋白 H3 赖氨酸 14 乙酰化水平降低，导致 elo3 突变体中的这些基因表达水平降低。在 elo 突变体的转录组中，其他与生长素相关的基因下调，但不被 Elongator HAT 活性靶向，这表明在靶基因选择方面具有特异性。在 elo 转录组中，乙烯和茉莉酸信号以及非生物胁迫反应上调，这可能导致了多效性 elo 表型。因此，尽管 Elongator 的结构及其底物保持保守，但靶基因选择已经出现分歧，表明生长素信号和流入受到染色质控制。
