Xu Xiaolu, Wei Shuo
Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA.
bioRxiv. 2025 Feb 9:2025.02.08.637260. doi: 10.1101/2025.02.08.637260.
The DEAD-box RNA helicase DDX3X has important roles in development and disease. Loss of DDX3X during developmental and pathological processes such as tumorigenesis can lead to compensatory upregulation of the close paralog DDX3Y in males, which may underlie the sexual dimorphism displayed by some DDX3X-associated diseases. However, how DDX3X cross-regulates DDX3Y remains largely unknown. Here, we investigated the regulation of DDX3Y by DDX3X in two male-derived human cancer cell lines, HCT116 and U87MG. Depletion of DDX3X in HCT116 cells results in moderately increased DDX3Y mRNA and protein, in part due to stabilization of transcripts. Conversely, reduction of DDX3X in U87MG cells markedly upregulates DDX3Y protein without affecting its mRNA, mainly by enhancing DDX3Y protein stability. We further show that DDX3X physically interacts with DDX3Y. DDX3Y is much less stable than DDX3X in U87MG cells, and substitution of two lysine residues in DDX3Y with the corresponding arginine in DDX3X stabilizes DDX3Y. Thus, the compensatory upregulation of DDX3Y following DDX3X loss can occur at either transcript or protein level, suggesting complex and cell type-specific cross-regulation between these X- and Y-linked paralogs to keep the total DDX3 dosage in check.
DEAD盒RNA解旋酶DDX3X在发育和疾病中发挥着重要作用。在发育和病理过程（如肿瘤发生）中DDX3X的缺失可导致男性中密切相关的旁系同源物DDX3Y的代偿性上调，这可能是一些与DDX3X相关疾病所表现出的性别二态性的基础。然而，DDX3X如何交叉调节DDX3Y在很大程度上仍然未知。在此，我们在两种源自男性的人类癌细胞系HCT116和U87MG中研究了DDX3X对DDX3Y的调节作用。HCT116细胞中DDX3X的缺失导致DDX3Y mRNA和蛋白适度增加，部分原因是转录本的稳定性增加。相反，U87MG细胞中DDX3X的减少显著上调DDX3Y蛋白而不影响其mRNA，主要是通过增强DDX3Y蛋白的稳定性。我们进一步表明DDX3X与DDX3Y发生物理相互作用。在U87MG细胞中，DDX3Y比DDX3X稳定性低得多，并且用DDX3X中的相应精氨酸取代DDX3Y中的两个赖氨酸残基可使DDX3Y稳定。因此，DDX3X缺失后DDX3Y的代偿性上调可在转录本或蛋白水平发生，这表明这些X和Y连锁的旁系同源物之间存在复杂且细胞类型特异性的交叉调节，以控制DDX3的总量。
