Project description:The MYC oncogene has been implicated in the regulation of up to thousands of genes involved in many cellular programs including proliferation, growth, differentiation, self-renewal, and apoptosis. MYC is thought to induce cancer through an exaggerated effect on these physiologic programs. Which of these genes are responsible for the ability of MYC to initiate and/or maintain tumorigenesis is not clear. Previously, we have shown that upon brief MYC inactivation, some tumors undergo sustained regression. Here we demonstrate that upon MYC inactivation there are global permanent changes in gene expression detected by microarray analysis. By applying StepMiner analysis, we identified genes whose expression most strongly correlated with the ability of MYC to induce a neoplastic state. Notably, genes were identified that exhibited permanent changes in mRNA expression upon MYC inactivation. Importantly, permanent changes in gene expression could be shown by chromatin immunoprecipitation (ChIP) to be associated with permanent changes in the ability of MYC to bind to the promoter regions. Our list of candidate genes associated with tumor maintenance was further refined by comparing our analysis with other published results to generate a gene signature associated with MYC-induced tumorigenesis in mice. To validate the role of gene signatures associated with MYC in human tumorigenesis, we examined the expression of human homologs in 273 published human lymphoma microarray datasets in Affymetrix U133A format. One large functional group of these genes included the ribosomal structural proteins. In addition, we identified a group of genes involved in a diverse array of cellular functions including: BZW2, H2AFY, SFRS3, NAP1L1, NOLA2, UBE2D2, CCNG1, LIFR, FABP3, and EDG1. Hence, through our analysis of gene expression in murine tumor models and human lymphomas, we have identified a novel gene signature correlated with the ability of MYC to maintain tumorigenesis. Time: time of doxycycline treatment or time after removal Keywords: time_series_design Groups of assays that are related as part of a time series. Compound Based Treatment: Bone tumor cells 1325 were treated/not treated with 20ng/ml of doxycycline Computed
Project description:In addition to genomic alterations, aberrant changes in post-transcriptional regulation can modify gene function and drive cancer development. RNA-binding proteins (RBPs) are a large class of post-transcriptional regulators that have been increasingly implicated in carcinogenesis. By integrating multi-omics data, we identify LARP1 as one of the most upregulated RBPs in colorectal cancer (CRC), and demonstrate its oncogenic properties. We perform LARP1:RNA interactome profiling and unveil a previously unexplored role for LARP1 in targeting the 3′UTR of oncogenes in CRC. Notably, we identify the proto-oncogenic transcription factor MYC as a key LARP1-regulated target. Our data show that LARP1 positively modulates MYC expression by associating with its 3′UTR. In addition, antisense oligonucleotide-mediated blocking of the interaction between LARP1 and the MYC 3′UTR reduces MYC expression and in vitro CRC growth. Furthermore, a systematic analysis of LARP1:protein interactions reveals IGF2BP3 and YBX1 as LARP1-interacting proteins that also regulate MYC expression and CRC development. Finally, we demonstrate that MYC reciprocally modulates LARP1 expression by targeting its enhancer. In summary, our data reveal a critical, previously uncharacterized role of LARP1 in promoting CRC tumorigenesis, validate its direct regulation of the proto-oncogene MYC, and delineate a model of the positive feedback loop between MYC and LARP1 that promotes CRC growth and development.
Project description:Post-translational regulation of the MYC Transcription Factor (TF), including its phosphorylation and ubiquitination, plays an important role in determining cell proliferation and apoptosis and has been implicated in tumorigenesis. Using a computational systems biology approach, followed by biochemical and functional validation, we have characterized the role of the STK38 kinase, an NDR family serine-threonine kinase, as a key modulator of MYC transcriptional activity in human B cells, affecting MYC protein stability in a signal-dependent fashion. Specifically, we show that in human B lymphoma ST486 cells STK38 is a key mediator of BCR pathway signaling, affecting MYC protein turnover and its phosphorylation at Ser62 in kinase-activity-dependent manner. STK38 inactivation abrogates apoptosis following BCR activation while its silencing mediates MYC protein degradation via canonical proteolytic pathways. This suggests that STK38 could provide an effective therapeutic target in MYC-dependent malignancies. ST486 human Burkitt's lymphoma cells were transduced with STK38 shRNA lentiviral vectors.
Project description:Myc is an oncogenic transcription factor frequently dysregulated in human cancer. To identify pathways supporting the Myc oncogenic program, we employed a genome-wide RNAi screen for Myc-synthetic-lethal (MySL) genes and uncovered a role for the SUMO-activating-enzyme (SAE1/2). Loss of SAE1/2 enzymatic activity drives synthetic lethality with Myc. Mechanistically, SAE2 inhibition switches a transcriptional subprogram of Myc from activated to repressed. A subset of these SUMOylation-dependent Myc-switchers (SMS genes) governs mitotic spindle function and is required to support the Myc oncogenic program. comparison of 4 treatments: normal HMEC, High Myc in HMEC, SUMO depleted in HMEC, High Myc+Sumo Depleted in HMEC
Project description:It remains unclear how epigenetic modulators impact the tumorigenic potential of Myc. Here we show that the core subunits, including Dpy30, of the major H3K4 methyltransferase complexes are selectively upregulated in Burkitt lymphoma, and Dpy30 is important for efficient genomic binding of Myc. Dpy30 heterozygosity does not affect normal animal physiology, but significantly suppressed lymphomagenesis and reduced expression of a subset of key pro-survival genes when Myc is hyper-activated. Dpy30 heterozygosity also impedes cellular transformation without affecting normal cell growth. These results suggest that Myc hijacks this chromatin modulator to coordinate its oncogenic program for efficient tumorigenesis, meanwhile creating “epigenetic vulnerability”, which we then exploited by specifically targeting Dpy30’s activity to inhibit growth of the Burkitt lymphoma cell model.
Project description:It remains unclear how epigenetic modulators impact the tumorigenic potential of Myc. Here we show that the core subunits, including Dpy30, of the major H3K4 methyltransferase complexes are selectively upregulated in Burkitt lymphoma, and Dpy30 is important for efficient genomic binding of Myc. Dpy30 heterozygosity does not affect normal animal physiology, but significantly suppressed lymphomagenesis and reduced expression of a subset of key pro-survival genes when Myc is hyper-activated. Dpy30 heterozygosity also impedes cellular transformation without affecting normal cell growth. These results suggest that Myc hijacks this chromatin modulator to coordinate its oncogenic program for efficient tumorigenesis, meanwhile creating “epigenetic vulnerability”, which we then exploited by specifically targeting Dpy30’s activity to inhibit growth of the Burkitt lymphoma cell model.
Project description:MYC oncogenes are activated in broad spectrum of human malignancies and transcriptionally reprogram the genome to drive cancer cell growth. Given this it is unclear if targeting a single effector will have a therapeutic benefit. MYC activates the polyaminehypusine circuit, which post-translationally modifies the translation factor eIF5A. The hypusine axis has been proposed to suppress tumorigenesis. Here we report essential roles for hypusinated eIF5A in the development and maintenance of Myc-driven lymphoma, where loss of eIF5A hypusination abolishes malignant transformation. Mechanistically, integrating RNA-seq, Ribo-seq and proteomic analyses revealed that efficient translation of select targets is dependent upon eIF5A hypusination, including key regulators of G1 to S phase cell cycle progression. Notably, this circuit controls Myc’s proliferative response at several levels, and it is activated across multiple tumor types. These findings suggest the hypusine circuit as a therapeutic target for a broad spectrum of malignancies.
Project description:Splicing is a central RNA-based process commonly altered in human cancers; however, how the splicing machinery is co-opted during tumorigenesis remains largely unresolved. Here we identify the splice factor SF3A3 at the nexus of an oncogenic translation program that rewires splicing to promote tumorigenesis. Our results suggest that key spliceosomal networks centered on the essential core U2-associated factor, SF3A3, are exquisitely controlled at the translation level during oncogenic stress. Upon oncogene activation, SF3A3 translation is rapidly enabled via a conserved internal stem-loop structure embedded in the transcript 5’ untranslated region (UTR). Uncoupled SF3A3 translation leads to alternative splicing of several mRNAs involved in mitochondrial dynamics, and induces a metabolic switch that fuels cancer initiation properties in MYC-driven breast tumorigenesis in vivo. Finally, we compelling show that SF3A3 is post-transcriptionally altered and predicts for poor prognosis in aggressive triple negative breast cancers. Together, these findings unveil a highly dynamic regulatory network that interfaces mRNA splicing and translation to orchestrate cancer gene expression networks.