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Diverse mechanisms of DDX3Y suppression by DDX3X
1Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA.
Abstract:
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 DDX3Y 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.
Insights
Loss of DDX3X RNA helicase in males can cause compensatory DDX3Y upregulation. This cross-regulation occurs at mRNA or protein levels, depending on cell type, to maintain DDX3 dosage.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- The DEAD-box RNA helicase DDX3X is crucial for development and disease.
- Loss of DDX3X can lead to compensatory DDX3Y upregulation in males, potentially explaining sexual dimorphism in DDX3X-related diseases.
- Mechanisms of DDX3X-DDX3Y cross-regulation are largely unknown.
Purpose of the Study:
- Investigate the regulation of DDX3Y by DDX3X in male human cancer cell lines.
- Elucidate the mechanisms underlying DDX3Y upregulation upon DDX3X depletion.
Main Methods:
- Depletion of DDX3X in HCT116 and U87MG cell lines.
- Analysis of DDX3Y mRNA and protein levels.
- Assessment of transcript and protein stability.
- Investigation of physical interaction between DDX3X and DDX3Y.
- Site-directed mutagenesis to assess protein stability.
Main Results:
- DDX3X depletion moderately increased DDX3Y mRNA and protein in HCT116 cells, partly via transcript stabilization.
- DDX3X reduction markedly upregulated DDX3Y protein, but not mRNA, in U87MG cells, primarily through enhanced protein stability.
- DDX3X physically interacts with DDX3Y.
- Specific lysine residues in DDX3Y contribute to its lower stability compared to DDX3X.
Conclusions:
- Compensatory DDX3Y upregulation after DDX3X loss occurs via transcript or protein stabilization, depending on the cell type.
- Complex, cell type-specific cross-regulation exists between DDX3X and DDX3Y to maintain total DDX3 levels.
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