Sex differences are pervasive in human health and disease. One major key to sex-biased differences lies in the sex chromosomes. Although the functions of the X chromosome proteins are well appreciated, how they compare with their Y chromosome homologs remains elusive. Herein, using ensemble and single-molecule techniques, we report that the sex chromosome-encoded RNA helicases DDX3X and DDX3Y are distinct in their propensities for liquid-liquid phase separation (LLPS), dissolution, and translation repression. We demonstrate that the N-terminal intrinsically disordered region of DDX3Y more strongly promotes LLPS than the corresponding region of DDX3X and that the weaker ATPase activity of DDX3Y, compared with DDX3X, contributes to the slower disassembly dynamics of DDX3Y-positive condensates. Interestingly, DDX3Y-dependent LLPS represses mRNA translation and enhances aggregation of FUS more strongly than DDX3X-dependent LLPS. Our study provides a platform for future comparisons of sex chromosome-encoded protein homologs, providing insights into sex differences in RNA metabolism and human disease.

性别差异在人类健康和疾病中普遍存在。性别差异的一个主要关键在于性染色体。尽管 X 染色体蛋白的功能已广为人知，但它们如何与 Y 染色体同源物进行比较仍然难以捉摸。在此，利用整体和单分子技术，我们报告性染色体编码的RNA解旋酶DDX3X和DDX3Y在液-液相分离(LLPS)、溶解和翻译抑制方面具有不同的倾向。我们证明，DDX3Y 的 N 端本质无序区域比 DDX3X 的相应区域更强烈地促进 LLPS，并且与 DDX3X 相比，DDX3Y 的 ATP 酶活性较弱，导致 DDX3Y 阳性缩合物的分解动力学较慢。有趣的是，DDX3Y 依赖性 LLPS 比 DDX3X 依赖性 LLPS 更能抑制 mRNA 翻译并增强 FUS 聚集。我们的研究为未来比较性染色体编码的蛋白质同源物提供了一个平台，从而深入了解 RNA 代谢和人类疾病的性别差异。