Combinatorial interactions between different regulators diversify and enrich the chance of transcriptional regulation in eukaryotic cells. However, a dose-dependent functional switch of homologous transcriptional repressors has rarely been reported. Here, we show that SHY2, an auxin/indole-3-acetic acid (Aux/IAA) repressor, exhibits a dose-dependent bimodal role in auxin-sensitive root-hair growth and gene transcription in , whereas other Aux/IAA homologs consistently repress the auxin responses. The co-repressor (TOPLESS [TPL])-binding affinity of a bimodal Aux/IAA was lower than that of a consistently repressing Aux/IAA. The switch of a single amino acid residue in the TPL-binding motif between the bimodal form and the consistently repressing form switched their TPL-binding affinity and transcriptional and biological roles in auxin responses. Based on these data, we propose a model whereby competition between homologous repressors with different co-repressor-binding affinities could generate a bimodal output at the transcriptional and developmental levels.

中文翻译：

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同源 Aux/IAA 转录抑制因子的剂量依赖性双峰开关


不同调节因子之间的组合相互作用使真核细胞转录调节的机会多样化并丰富。然而，同源转录抑制因子的剂量依赖性功能开关很少有报道。在这里，我们发现 SHY2 是一种生长素/吲哚-3-乙酸 (Aux/IAA) 阻遏物，在生长素敏感的根毛生长和基因转录中表现出剂量依赖性双峰作用，而其他 Aux/IAA 同源物始终如一抑制生长素反应。双峰 Aux/IAA 的共抑制子 (TOPLESS [TPL]) 结合亲和力低于持续抑制 Aux/IAA。 TPL 结合基序中单个氨基酸残基在双峰形式和持续抑制形式之间的转换改变了它们的 TPL 结合亲和力以及在生长素反应中的转录和生物学作用。基于这些数据，我们提出了一个模型，通过该模型，具有不同共阻遏物结合亲和力的同源阻遏物之间的竞争可以在转录和发育水平上产生双峰输出。