The recent discovery of the bona-fide telomerase RNA (TR) from plants reveals conserved and unique secondary structure elements and the opportunity for new insight into the telomerase RNP. Here we examine how two highly conserved proteins previously implicated in Arabidopsis telomere maintenance, AtPOT1a and AtNAP57 (dyskerin), engage plant telomerase. We report that AtPOT1a associates with Arabidopsis telomerase via interaction with TERT. While loss of AtPOT1a does not impact AtTR stability, the templating domain is more accessible in pot1a mutants, supporting the conclusion that AtPOT1a stimulates telomerase activity but does not facilitate telomerase RNP assembly. We also show, that despite the absence of a canonical H/ACA binding motif within AtTR, dyskerin binds AtTR with high affinity and specificity in vitro via a plant specific three-way junction (TWJ). A core element of the TWJ is the P1a stem, which unites the 5′ and 3′ ends of AtTR. P1a is required for dyskerin-mediated stimulation of telomerase repeat addition processivity in vitro, and for AtTR accumulation and telomerase activity in vivo. The deployment of vertebrate-like accessory proteins and unique RNA structural elements by Arabidopsis telomerase provides a new platform for exploring telomerase biogenesis and evolution.

中文翻译：

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拟南芥通过植物特异性组装保留脊椎动物型端粒酶辅助蛋白

最近从植物中发现的真正的端粒酶 RNA (TR) 揭示了保守和独特的二级结构元件，以及对端粒酶 RNP 的新见解的机会。在这里，我们研究了以前与拟南芥端粒维持有关的两种高度保守的蛋白质 AtPOT1a 和 AtNAP57 (dyskerin) 如何与植物端粒酶结合。我们报告 AtPOT1a 通过与 TERT 的相互作用与拟南芥端粒酶相关联。虽然 AtPOT1a 的丢失不会影响 AtTR 稳定性，模板域在 pot1a 突变体中更容易获得，支持 AtPOT1a 刺激端粒酶活性但不促进端粒酶 RNP 组装的结论。我们还表明，尽管 AtTR 中没有规范的 H/ACA 结合基序，在体外，dyskerin 通过植物特异性三向连接 (TWJ) 以高亲和力和特异性结合 AtTR。TWJ 的核心元素是 P1a 茎，它连接 AtTR 的 5' 和 3' 端。P1a 是肌动蛋白介导的端粒酶重复添加过程体外刺激和体内 AtTR 积累和端粒酶活性所必需的。拟南芥端粒酶对类脊椎动物辅助蛋白和独特RNA结构元件的部署为探索端粒酶的生物发生和进化提供了新的平台。