Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France.
Cell Res. 2010 Dec;20(12):1332-44. doi: 10.1038/cr.2010.151. Epub 2010 Nov 9.
Polycomb group genes play crucial roles in the maintenance of the transcriptionally silenced state of genes for proper cell differentiation in animals and plants. While components of the polycomb repressive complex2 (PRC2) are evolutionarily conserved and their functions are extensively studied in plants, PRC1 differs considerably between animals and plants, and its functions in plants are as yet not well described. Previous studies have identified the Arabidopsis AtRING1a and AtRING1b as homologues of the animal PRC1 subunit RING1. Here, we show that the Atring1a Atring1b double mutant exhibits derepression of embryonic traits during vegetative growth. Accordingly, several key regulatory genes involved in embryogenesis and stem cell activity are ectopically expressed in the mutant. Furthermore, we show that the mutant phenotypes and increased expression of regulatory genes are enhanced by the PRC2 mutant clf. Finally, we show that three homologues of the animal PRC1-subunit ring-finger protein BMI1, AtBMI1a, AtBMI1b and AtBMI1c, can bind with AtRING1a or AtRING1b, and in addition, AtBMI1c can bind with LHP1. The Atbmi1a Atbmi1b double mutant shows derepression of embryonic traits similar to that of the Atring1a Atring1b double mutant. Interestingly, expression levels of AtBMI1a, AtBMI1b and AtBMI1c are elevated in the Atring1a Atring1b mutant and those of AtBMI1c, AtRING1a and AtRING1b are elevated in the Atbmi1a Atbmi1b mutant, suggesting a self-regulatory feedback mechanism. Taken together, our results illuminate crucial functions of the PRC1-like ring-finger components in stable repression of embryonic traits and regulatory genes for proper somatic growth.
多梳组基因在动植物中对于适当的细胞分化起着至关重要的作用，它们可以维持基因转录沉默状态。虽然多梳抑制复合物 2（PRC2）的组成部分在进化上是保守的，并且其功能在植物中得到了广泛的研究，但 PRC1 在动物和植物之间有很大的不同，其在植物中的功能尚未得到很好的描述。以前的研究已经鉴定出拟南芥 AtRING1a 和 AtRING1b 是动物 PRC1 亚基 RING1 的同源物。在这里，我们表明 AtRING1a 和 AtRING1b 的双突变体在营养生长过程中表现出胚胎特征的去抑制。因此，几个参与胚胎发生和干细胞活性的关键调节基因在突变体中异位表达。此外，我们表明，突变体表型和调节基因的高表达在 PRC2 突变体 clf 的作用下增强。最后，我们表明，动物 PRC1 亚基环指蛋白 BMI1 的三个同源物 AtBMI1a、AtBMI1b 和 AtBMI1c 可以与 AtRING1a 或 AtRING1b 结合，此外，AtBMI1c 可以与 LHP1 结合。Atbmi1a Atbmi1b 的双突变体表现出与 AtRING1a AtRING1b 双突变体相似的胚胎特征去抑制。有趣的是，AtBMI1a、AtBMI1b 和 AtBMI1c 的表达水平在 AtRING1a AtRING1b 突变体中升高，而 AtBMI1c、AtRING1a 和 AtRING1b 的表达水平在 Atbmi1a Atbmi1b 突变体中升高，表明存在自我调节的反馈机制。总之，我们的研究结果阐明了 PRC1 样环指成分在稳定抑制胚胎特征和调节基因以实现适当体细胞生长中的关键功能。
