Project description:By using ribosome profiling, we demonstrate that catalytic activity of the RNA helicase DDX3 is generally required for mediating translation repression under stress. Intriguingly, however, a cancer-related DDX3 variant DDX3 R534H selectively preserves translation of genes encoding core nucleosome components. Additionally, DDX3 variants also shift ORF usage on select genes, such as RPLP1 and stress-response factors as an added mechanism of translation regulation during stress. Thus, DDX3 through both extensive and selective interactions with RNA and the ribosomal machinery helps to remodel the translational landscape under stress and in cancer.
Project description:We undertook a comprehensive clinical and biological investigation of serial medulloblastoma biopsies obtained at diagnosis and relapse. Combined MYC gene family amplifications and P53 pathway defects commonly emerged at relapse, and all patients in this molecular group died of rapidly progressive disease post-relapse. To study this genetic interaction, we investigated a transgenic model of MYCN-driven medulloblastoma and found spontaneous development of Trp53 inactivating mutations. Abrogation of Trp53 function in this model produced aggressive tumors that mimicked the characteristics of relapsed human tumors with combined P53-MYC dysfunction. Restoration of p53 activity, genetic and therapeutic suppression of MYCN all reduced tumor growth and prolonged survival. Our findings identify P53–MYC interactions which emerge at medulloblastoma relapse as biomarkers of clinically aggressive disease that may be targeted therapeutically. Using this dataset, assignation of medulloblastoma molecular subgroup by Illumina 450k microarray was performed for diagnostic and relapsed medulloblastoma samples to compare subgroup membership at diagnosis and relapse.
Project description:Metabolic dysfunction-associated steatohepatitis (MASH) and its progression to hepatocellular carcinoma remain major clinical challenges. Chronic endoplasmic reticulum (ER) stress, induced by sustained high-fat diet (HFD) intake, promotes hepatic inflammation, lipid accumulation, and hepatocellular dysfunction during MASH pathogenesis. While transcriptional responses are well-characterized, the post-transcriptional mechanisms underlying hepatocyte adaptation to chronic ER stress remain poorly understood. Using an integrative approach combining transcriptomics, ribosome profiling, cytoplasmic polyadenylation analysis, and cis-regulatory mapping, we define the post-transcriptional landscape induced by chronic HFD exposure. To delineate the specific role of chronic ER stress, we use a hepatocyte-specific knockout of a key regulator of translational control under prolonged ER stress. We show that ~70% of HFD-induced gene expression changes are modulated at the translational level. A distinct subset of mRNAs - enriched in suboptimal codons and bearing short poly(A) tails under normal diet - becomes selectively activated upon HFD-induced poly(A) tail elongation. These transcripts, associated with cell cycle, immune response, fibrosis, and tissue remodeling, correlate with MASH severity in both murine models and human samples. Their regulation is mediated by cis-elements in the 3' UTR that coordinate polyadenylation and deadenylation. Loss of this adaptive response exacerbates liver damage and tumor burden in HFD-fed mice.
Project description:Metabolic dysfunction-associated steatohepatitis (MASH) and its progression to hepatocellular carcinoma remain major clinical challenges. Chronic endoplasmic reticulum (ER) stress, induced by sustained high-fat diet (HFD) intake, promotes hepatic inflammation, lipid accumulation, and hepatocellular dysfunction during MASH pathogenesis. While transcriptional responses are well-characterized, the post-transcriptional mechanisms underlying hepatocyte adaptation to chronic ER stress remain poorly understood. Using an integrative approach combining transcriptomics, ribosome profiling, cytoplasmic polyadenylation analysis, and cis-regulatory mapping, we define the post-transcriptional landscape induced by chronic HFD exposure. To delineate the specific role of chronic ER stress, we use a hepatocyte-specific knockout of a key regulator of translational control under prolonged ER stress. We show that ~70% of HFD-induced gene expression changes are modulated at the translational level. A distinct subset of mRNAs - enriched in suboptimal codons and bearing short poly(A) tails under normal diet - becomes selectively activated upon HFD-induced poly(A) tail elongation. These transcripts, associated with cell cycle, immune response, fibrosis, and tissue remodeling, correlate with MASH severity in both murine models and human samples. Their regulation is mediated by cis-elements in the 3'UTR that coordinate polyadenylation and deadenylation. Loss of this adaptive response exacerbates liver damage and tumor burden in HFD-fed mice.
Project description:Metabolic dysfunction-associated steatohepatitis (MASH) and its progression to hepatocellular carcinoma remain major clinical challenges. Chronic endoplasmic reticulum (ER) stress, induced by sustained high-fat diet (HFD) intake, promotes hepatic inflammation, lipid accumulation, and hepatocellular dysfunction during MASH pathogenesis. While transcriptional responses are well-characterized, the post-transcriptional mechanisms underlying hepatocyte adaptation to chronic ER stress remain poorly understood. Using an integrative approach combining transcriptomics, ribosome profiling, cytoplasmic polyadenylation analysis, and cis-regulatory mapping, we define the post-transcriptional landscape induced by chronic HFD exposure. To delineate the specific role of chronic ER stress, we use a hepatocyte-specific knockout of a key regulator of translational control under prolonged ER stress. We show that ~70% of HFD-induced gene expression changes are modulated at the translational level. A distinct subset of mRNAs - enriched in suboptimal codons and bearing short poly(A) tails under normal diet - becomes selectively activated upon HFD-induced poly(A) tail elongation. These transcripts, associated with cell cycle, immune response, fibrosis, and tissue remodeling, correlate with MASH severity in both murine models and human samples. Their regulation is mediated by cis-elements in the 3' UTR that coordinate polyadenylation and deadenylation. Loss of this adaptive response exacerbates liver damage and tumor burden in HFD-fed mice.
Project description:Metabolic dysfunction-associated steatohepatitis (MASH) and its progression to hepatocellular carcinoma remain major clinical challenges. Chronic endoplasmic reticulum (ER) stress, induced by sustained high-fat diet (HFD) intake, promotes hepatic inflammation, lipid accumulation, and hepatocellular dysfunction during MASH pathogenesis. While transcriptional responses are well-characterized, the post-transcriptional mechanisms underlying hepatocyte adaptation to chronic ER stress remain poorly understood. Using an integrative approach combining transcriptomics, ribosome profiling, cytoplasmic polyadenylation analysis, and cis-regulatory mapping, we define the post-transcriptional landscape induced by chronic HFD exposure. To delineate the specific role of chronic ER stress, we use a hepatocyte-specific knockout of a key regulator of translational control under prolonged ER stress. We show that ~70% of HFD-induced gene expression changes are modulated at the translational level. A distinct subset of mRNAs - enriched in suboptimal codons and bearing short poly(A) tails under normal diet - becomes selectively activated upon HFD-induced poly(A) tail elongation. These transcripts, associated with cell cycle, immune response, fibrosis, and tissue remodeling, correlate with MASH severity in both murine models and human samples. Their regulation is mediated by cis-elements in the 3' UTR that coordinate polyadenylation and deadenylation. Loss of this adaptive response exacerbates liver damage and tumor burden in HFD-fed mice.
Project description:Deregulation of N-myc is a leading cause of malignant brain tumors in children. To target N-myc-driven medulloblastoma, most research has focused on identifying genomic alterations or on the analysis of the medulloblastoma transcriptome. Here, we have broadly characterized the translatome of medulloblastoma and shown that N-myc unexpectedly drives selective translation of transcripts that promote protein homeostasis. Cancer cells are constantly exposed to proteotoxic stress associated with alterations in protein production or folding. It remains poorly understood how cancers cope with proteotoxic stress to promote their growth. Here, our data unexpectedly revealed that N-myc regulates the expression of specific components (~5%) of the protein folding machinery at the translational level through the major cap binding protein, eukaryotic initiation factor eIF4E. Reducing eIF4E levels in mouse models of medulloblastoma blocked tumorigenesis. Importantly, targeting Hsp70, a protein folding chaperone translationally regulated by N-myc, suppressed tumor growth in mouse and human medulloblastoma xenograft models. These findings reveal a previously hidden molecular program that promotes medulloblastoma formation and identify new therapies that may have impact in the clinic.
Project description:We undertook a comprehensive clinical and biological investigation of serial medulloblastoma biopsies obtained at diagnosis and relapse. Combined MYC gene family amplifications and P53 pathway defects commonly emerged at relapse, and all patients in this molecular group died of rapidly progressive disease post-relapse. To study this genetic interaction, we investigated a transgenic model of MYCN-driven medulloblastoma and found spontaneous development of Trp53 inactivating mutations. Abrogation of Trp53 function in this model produced aggressive tumors that mimicked the characteristics of relapsed human tumors with combined P53-MYC dysfunction. Restoration of p53 activity, genetic and therapeutic suppression of MYCN all reduced tumor growth and prolonged survival. Our findings identify P53–MYC interactions which emerge at medulloblastoma relapse as biomarkers of clinically aggressive disease that may be targeted therapeutically. Using this dataset, assignation of medulloblastoma molecular subgroup by Illumina 450k microarray was performed for diagnostic and relapsed medulloblastoma samples to compare subgroup membership at diagnosis and relapse. We investigated the DNA methylation profiles of 18 diagnostic and 22 relapsing samples (including 15 diagnostic / relapse pairs) using the Illumina 450k methylation microarray
Project description:We report a novel resistance mechanism to CDK4/6 inhibition in Hedgehog-associated medulloblastoma where cell models and mouse models demonstrate that prolonged inhibition of CDK4/6 inhibits ribosome biogenesis, activates the unfolded protein response, and increases the amount of Smoothened-activating lipids. This RNA-Sequencing dataset represents genomically-engineered mouse medulloblastoma models that either have wild-type Cdk6 or genomic knockout of Cdk6. We find that tumors that grew despite genetic loss of Cdk6 have suppresed ribosome biogenesis.
Project description:In the present study we analyzed the response of S. aureus to mupirocin, the drug of choice for nasal decolonization of S. aureus. Mupirocin selectively inhibits the bacterial isoleucyl-tRNA synthetase (IleRSs) leading to the accumulation of uncharged isoleucyl-tRNA and hence (p)ppGpp. The latter is a signal for the induction of the stringent response, an important global transcriptional and translational control mechanism that allows bacteria to adapt to nutritional deprivation. To identify proteins with an altered synthesis pattern in response to mupirocin treatment we used the highly sensitive 2-dimensional gel electrophoresis technique in combination with mass spectrometry. Obtained results were complemented by DNA-microarray, Northern blot and metabolome analysis. Whereas expression of genes involved in nucleotide biosynthesis, DNA metabolism, energy metabolism and translation was significantly down-regulated, expression of the isoleucyl-tRNA synthetase, the branched chain amino acids pathway, genes with functions in oxidative stress resistance (ahpC, katA), putative roles in stress protection (SACOL1759, SACOL2131, SACOL0815) and transport processes was increased. Of particular interest were the differences in the transcription of genes encoding virulence associated regulators (i.e. arlRS, saeRS, sarA, sarR, sarS) as well as genes directly involved in the virulence of S. aureus (i.e. fnbA, epiE, epiG, seb). In the present study we analyzed the response of S. aureus to mupirocin, the drug of choice for nasal decolonization of S. aureus. Mupirocin selectively inhibits the bacterial isoleucyl-tRNA synthetase (IleRSs) leading to the accumulation of uncharged isoleucyl-tRNA and hence (p)ppGpp. The latter is a signal for the induction of the stringent response, an important global transcriptional and translational control mechanism that allows bacteria to adapt to nutritional deprivation. In total four independent hybridization experiments with each representing a biological replicate including a control and a treated sample were carried out. To account for the dye bias two of the four replicates were dye swapped.