DELLA protein functions as a transcriptional activator through the DNA binding of the INDETERMINATE DOMAIN family proteins
DELLA protein functions as a transcriptional activator through the DNA binding of the INDETERMINATE DOMAIN family proteins
复制标题
DOI：
10.1073/pnas.1321669111
复制
发表时间：
2014-05
期刊：
影响因子：
--
通讯作者：
H. Yoshida;K. Hirano;Tomomi Sato;Nobutaka Mitsuda;Mika Nomoto;K. Maeo;Eriko Koketsu;Rie Mitani
中科院分区：
文献类型：
--
作者：
H. Yoshida;K. Hirano;Tomomi Sato;Nobutaka Mitsuda;Mika Nomoto;K. Maeo;Eriko Koketsu;Rie Mitani
DELLA蛋白是赤霉素（GA）的一个重要的负调节因子，其降解是GA发挥作用的关键.然而，目前还不清楚DELLA如何调节下游基因表达。DELLA虽然具有很强的反式激活活性，但缺乏DNA结合结构域。因此，已经提出了一个模型，其中DELLA作为转录共激活因子与另一个转录因子或含有DNA结合结构域的因子。在这里，我们表明，一些成员的INEMPLATE域（IDD）蛋白质家族是这样的中间蛋白质。DELLA/IDD复合物上调GA阳性调节因子SCARECROW-LIKE 3（SCL 3）的表达。同时，SCL 3蛋白也与IDD蛋白相互作用，抑制自身的表达。我们认为DELLA（作为辅激活因子）和SCL 3（作为辅抑制因子）之间的辅调节因子交换系统调节SCL 3的表达。DELLA蛋白是赤霉素（GA）信号转导的关键负调控因子。尽管DELLA如何调节下游基因表达仍不清楚，但DELLA已被提出作为转录激活因子发挥作用。然而，由于DELLA缺乏DNA结合结构域，因此介导DELLA/DNA相互作用的中间蛋白被认为是激活DELLA靶基因所必需的。在这里，使用酵母杂交筛选，我们鉴定了不确定域（IDD）蛋白家族的五个成员，它们与DELLA和GA阳性调节因子SCARECROW-LIKE 3（SCL 3）的启动子序列物理结合，后者之前被描述为DELLA直接靶基因。利用拟南芥原生质体的瞬时测定表明，由SCL 3启动子控制的荧光素酶报告基因被GA 1 -3（RGA）和IDDs的RESIOR加成反式激活。表型分析的转基因植物表达AtIDD 3（拟南芥基因组中的16 IDDs之一）融合植物特异性阻遏结构域（SRDX）支持的可能性，AtIDD 3是积极参与GA信号。此外，我们发现SCL 3蛋白还与IDDs相互作用，导致其靶基因表达受到抑制。在这种情况下，DELLA和SCL 3竞争性地与IDD蛋白相互作用以调节下游基因表达。这些结果表明，辅助调节DELLA和SCL 3，使用IDDs作为DNA结合的转录支架，拮抗性地调节其下游靶点的表达，以控制GA信号通路。
Significance Gibberellin (GA)-dependent degradation of DELLA protein, a key negative regulator, is essential for GA action. However, it is unclear how DELLA regulates downstream gene expression. Although possessing strong transactivation activity, DELLA lacks a DNA-binding domain. Therefore, a model has been proposed in which DELLA acts as a transcriptional coactivator with another transcription factor or factors containing a DNA-binding domain. Here, we show that some members of the INDETERMINATE DOMAIN (IDD) protein family are such intermediate proteins. The DELLA/IDD complex up-regulates the expression of the GA-positive regulator SCARECROW-LIKE 3 (SCL3). Meanwhile, SCL3 protein also interacts with IDD proteins to suppress its own expression. We propose that a coregulator exchange system between DELLA (as coactivator) and SCL3 (as corepressor) regulates the expression of SCL3. DELLA protein is a key negative regulator of gibberellin (GA) signaling. Although how DELLA regulates downstream gene expression remains unclear, DELLA has been proposed to function as a transcriptional activator. However, because DELLA lacks a DNA-binding domain, intermediate protein(s) mediating the DELLA/DNA interaction are believed to be necessary for activating DELLA target genes. Here, using yeast hybrid screenings, we identified five members of INDETERMINATE DOMAIN (IDD) protein family which bind physically to both DELLA and the promoter sequence of the GA-positive regulator SCARECROW-LIKE 3 (SCL3), which previously was characterized as a DELLA direct target gene. Transient assays using Arabidopsis protoplasts demonstrated that a luciferase reporter controlled by the SCL3 promoter was additively transactivated by REPRESSOR of ga1-3 (RGA) and IDDs. Phenotypic analysis of transgenic plants expressing AtIDD3 (one of the 16 IDDs in the Arabidopsis genome) fused with the plant-specific repression domain (SRDX) supported the possibility that AtIDD3 is positively involved in GA signaling. In addition, we found that SCL3 protein also interacts with IDDs, resulting in the suppression of its target gene expression. In this context, DELLA and SCL3 interact competitively with IDD proteins to regulate downstream gene expression. These results suggest that the coregulators DELLA and SCL3, using IDDs as transcriptional scaffolds for DNA binding, antagonistically regulate the expression of their downstream targets to control the GA signaling pathway.