Loss of the deubiquitinase USP36 destabilizes the RNA helicase DHX33 and causes preimplantation lethality in mice

Julia M Fraile, Diana Campos-Iglesias, Francisco Rodríguez, Aurora Astudillo, Roser Vilarrasa-Blasi, Nuria Verdaguer-Dot, Miguel A Prado, Joao A Paulo, Steven P Gygi, José I Martín-Subero, José M P Freije, Carlos López-Otín

Deubiquitinases are proteases with a wide functional diversity that profoundly impact multiple biological processes. Among them, the ubiquitin-specific protease 36 (USP36) has been implicated in the regulation of nucleolar activity. However, its functional relevance in vivo has not yet been fully described. Here, we report the generation of an Usp36-deficient mouse model to examine the function of this enzyme. We show that Usp36 depletion is lethal in pre-implantation mouse embryos, where it blocks the transition from morula to blastocyst during embryonic development. USP36 reduces the ubiquitination levels and increases the stability of the DEAH box RNA helicase DHX33, which is critically involved in ribosomal RNA synthesis and mRNA translation. In agreement with this finding, O-propargyl-puromycin incorporation experiments, Northern Blot and electron microscopy analyses demonstrated the role of USP36 in ribosomal RNA and protein synthesis. Finally, we show that USP36 downregulation alters cell proliferation in human cancer cells by inducing both apoptosis and cell cycle arrest, and that reducing DHX33 levels through shRNA interference has the same effect. Collectively, these results support that Usp36 is essential for cell and organism viability because of its role in ribosomal RNA processing and protein synthesis, which is mediated, at least in part, by regulating DHX33 stability.