• RNA polymerase II (Pol II) associated proteins (RPAPs) have been ascribed diverse functions at the cellular level; however, their roles in developmental processes in yeasts, animals and plants are very poorly understood.
• Through screening for interactors of NRPB3, which encodes the third largest subunit of Pol II, we identified RIMA, the orthologue of mammalian RPAP2. A combination of genetic and biochemical assays revealed the role of RIMA and other RPAPs in stomatal development in Arabidopsis thaliana.
• We show that RIMA is involved in nuclear import of NRPB3 and other Pol II subunits, and is essential for restraining division and for establishing cell identity in the stomatal cell lineage. Moreover, plant RPAPs IYO/RPAP1 and QQT1/RPAP4, which interact with RIMA, are also crucial for stomatal development. Importantly, RIMA and QQT1 bind physically to stomatal transcription factors SPEECHLESS, MUTE, FAMA and SCREAMs.
• The RIMA‐QQT1‐IYO complex could work together with key stomatal transcription factors and Pol II to drive cell fate transitions in the stomatal cell lineage. Direct interactions with stomatal transcription factors provide a novel mechanism by which RPAP proteins may control differentiation of cell types and tissues in eukaryotes.

中文翻译：

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RNA聚合酶II相关蛋白通过与拟南芥气孔转录因子的直接相互作用调节气孔发育

• RNA 聚合酶 II (Pol II) 相关蛋白 (RPAP) 在细胞水平上具有多种功能；然而，人们对它们在酵母、动物和植物发育过程中的作用知之甚少。
• 通过筛选编码 Pol II 的第三大亚基的 NRPB3 的相互作用子，我们确定了哺乳动物 RPAP2 的直系同源物 RIMA。遗传和生化分析的结合揭示了 RIMA 和其他 RPAP 在拟南芥气孔发育中的作用。
• 我们表明 RIMA 参与 NRPB3 和其他 Pol II 亚单位的核输入，对于抑制分裂和在气孔细胞谱系中建立细胞身份至关重要。此外，与 RIMA 相互作用的植物 RPAP IYO/RPAP1 和 QQT1/RPAP4 对气孔发育也至关重要。重要的是，RIMA 和 QQT1 与气孔转录因子 SPEECHLESS、MUTE、FAMA 和 SCREAM 物理结合。
• RIMA-QQT1-IYO 复合物可以与关键的气孔转录因子和 Pol II 一起驱动气孔细胞谱系中的细胞命运转变。与气孔转录因子的直接相互作用提供了一种新的机制，RPAP 蛋白可以通过该机制控制真核生物中细胞类型和组织的分化。