Project description:FTSJ1 is a conserved human 2’-O-methyltransferase (Nm-MTase) that modifies several transfer RNAs (tRNAs) at position 32 and the wobble position 34 in the AntiCodon Loop (ACL). Its loss of function has been linked to Non-Syndromic X-Linked Intellectual Disability (NSXLID), and more recently to cancers. However, the molecular mechanisms underlying these pathologies are currently unclear. Here we report a novel FTSJ1 pathogenic variant from a NSXLID patient. Using blood cells derived from this patient and other affected individuals carrying FTSJ1 mutations, we performed an unbiased and comprehensive RiboMethSeq analysis to map the ribose methylation (Nm) on all tRNAs and identify novel targets. In addition, we performed a transcriptome analysis in these cells and found that several genes previously associated with intellectual disability and cancers were deregulated. We also found changes in the miRNA population that suggest potential cross-regulation of some miRNAs with these key mRNA targets. Finally, we show that differentiation of FTSJ1-depleted human neuronal progenitor cells (NPC) into neurons displays long and thin spine neurites compared to control cells. These defects are also observed in Drosophila and are associated with long term memory deficit in this organism. Altogether, our study adds insight into FTSJ1 pathologies in human by the identification of novel FTSJ1 targets and the defect in neuron morphology.
Project description:2’-O-methylation (Nm) represents one of the most common RNA modifications. Nm affects RNA structure and function with crucial roles in various RNA-mediated processes ranging from RNA silencing, translation, self versus non-self recognition to viral defense mechanisms. Here, we identify two novel Nm methyltransferases (Nm-MTases) in Drosophila melanogaster (CG7009 and CG5220) as functional orthologs of yeast TRM7 and human FTSJ1. Genetic knockout studies together with MALDI-TOF mass spectrometry and RiboMethSeq mapping revealed that CG7009 is responsible for methylating the wobble position in tRNAPhe, tRNATrp and tRNALeu, while subsequently, CG5220 methylates position C32 in the same tRNAs and targets also additional tRNAs. CG7009 or CG5220 mutant animals were viable and fertile but exhibited various phenotypes such as life span reduction, small RNA pathways dysfunction and increased sensitivity to RNA virus infections. Our results provide the first detailed characterization of two TRM7 family members in Drosophila and uncover a molecular link between enzymes catalysing Nm at specific tRNAs and small RNA-induced gene silencing pathways.
Project description:We report the application of RNA-sequencing for high-throughput profiling of transcriptomes in PC9 cells transfected with stably expressed FTSJ1.
Project description:Cancer-relevant signalling pathways rely on bidirectional nucleocytoplasmic transport events through the nuclear pore complex (NPC). However, mechanisms by which individual NPC components (Nups) participate in the regulation of these pathways remain poorly understood. We discovered by integrating large scale proteomics, polysome fractionation and a focused RNAi approach that Nup155 controls mRNA translation of p21 (CDKN1A), a key mediator of the p53 response. The underlying mechanism involves transcriptional regulation of the putative tRNA and rRNA methyltransferase FTSJ1 by Nup155. Furthermore, we observed that Nup155 and FTSJ1 are p53 repression targets and accordingly found a correlation between the p53 status, Nup155 and FTSJ1 expression in murine and human hepatocellular carcinoma (HCC). Our data suggest an unanticipated regulatory network linking translational control by and repression of a structural NPC component modulating the p53 pathway through its effectors.
Project description:Oxidative stress has been shown to limit metastasis of numerous cancer types including melanoma. A specialized group of 25 proteins containing the 21st amino acid, selenocysteine, plays a central role in oxidative stress resistance, which is a key driver of metastasis. A single selenocysteine tRNA methylation, Um34, is required for the translation of several stress-related selenoproteins in a selenium-dependent manner. Herein, we characterize FTSJ1 as the Um34 methyltransferase and show that its activity is required for the Sec tRNA (tRNASec) Um34 modification. Loss of Um34 affects translation of a subset of selenoproteins and increases melanoma cell sensitivity to oxidative stress while increased Um34 levels promote oxidative stress resistance. Loss of FTSJ1 does not affect primary melanoma tumor growth but abolishes metastatic spread in vivo. Overexpression of FTSJ1 specifically increases melanoma metastasis in vivo. Our work establishes FTSJ1 as the Um34 methyltransfearse and tRNASec Um34 modification as a central regulator of oxidative stress resistance during melanoma metastasis.