Axonemal dynein, the macromolecular machine that powers ciliary motility, assembles in the cytosol with the help of dynein axonemal assembly factors (DNAAFs). These DNAAFs localize in cytosolic foci thought to form via liquid–liquid phase separation. However, the functional significance of DNAAF foci formation and how the production and assembly of multiple components are so efficiently coordinated, at such enormous scale, remain unclear. Here, we unveil an axonemal dynein production and assembly hub enriched with translating heavy chains (HCs) and DNAAFs. We show that mRNAs encoding interacting HCs of outer dynein arms colocalize in cytosolic foci, along with nascent HCs. The formation of these mRNA foci and their colocalization relies on HC translation. We observe that a previously identified DNAAF assembly, containing the DNAAF Lrrc6 and cochaperones Ruvbl1 and Ruvbl2, colocalizes with these HC foci, and is also dependent on HC translation. We additionally show that Ruvbl1 is required for the recruitment of Lrrc6 into the HC foci and that both proteins function cotranslationally. We propose that these DNAAF foci are anchored by stable interactions between translating HCs, ribosomes, and encoding mRNAs, followed by cotranslational molecular condensation of cochaperones and assembly factors, providing a potential mechanism that coordinates HC translation, folding, and assembly at scale.

中文翻译：

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伴侣和组装因子的共翻译分子缩合促进轴丝动力蛋白生物发生


轴丝动力蛋白是驱动纤毛运动的大分子机器，在动力蛋白轴丝组装因子 （DNAAF） 的帮助下组装在胞质溶胶中。这些 DNAAF 定位于被认为通过液-液相分离形成的胞质病灶中。然而，DNAAF 病灶形成的功能意义以及多个组分的生产和组装如何在如此巨大的规模下如此有效地协调，仍不清楚。在这里，我们推出了一个富含翻译重链 （HC） 和 DNAAF 的轴丝动力蛋白生产和组装中心。我们表明，编码动力蛋白外臂相互作用的 HC 的 mRNA 与新生的 HC 一起共定位在胞质病灶中。这些 mRNA 病灶的形成及其共定位依赖于 HC 翻译。我们观察到，先前鉴定的包含 DNAAF Lrrc6 和共伴侣 Ruvbl1 和 Ruvbl2 的 DNAAF 组装体与这些 HC 病灶共定位，并且也依赖于 HC 翻译。我们还表明 Ruvbl1 是将 Lrrc6 募集到 HC 病灶所必需的，并且两种蛋白质都具有共翻译功能。我们提出这些 DNAAF 病灶以翻译 HCs、核糖体和编码 mRNA 之间的稳定相互作用为基础，然后是共伴侣和组装因子的共翻译分子缩合，提供了一种大规模协调 HC 翻译、折叠和组装的潜在机制。