Project description:MYC controls the transcription of large numbers of long non-coding RNAs. Since MYC is a ubiquitous oncoprotein, some of these long non-coding RNAs (lncRNAs) probably play a significant role in cancer. We applied CRISPRi to the identification of MYC-regulated lncRNAs that are required for MYC-driven cell proliferation in the P493-6 and RAMOS human lymphoid cell lines. We identified 320 non-coding loci that play a positive role in cell growth. Transcriptional repression of any one of these lncRNAs reduces the proliferative capacity of the cells. Selected hits were validated by RTqPCR and in CRISPRi-competition assays with individual GFP-expressing sgRNA-constructs. We also showed binding of MYC to the promoter of two candidate genes by chromatin immunoprecipitation. In the course of our studies, we discovered that the repressor domain SID derived from the MXD1 protein is highly effective in P493-6 and RAMOS cells in terms of the number of guides depleted in library screening and the extent of the induced transcriptional repression. In the cell lines used, it is superior to the KRAB repressor domain which serves routinely as transcriptional repressor domain in CRISPRi. The SID transcriptional repressor domain is effective as a fusion to the MS2 aptamer binding protein MCP allowing the construction of a doxycycline regulatable CRISPRi-system that allows controlled repression of targeted genes and will facilitate the functional analysis of growth-promoting lncRNAs.
Project description:MYC controls the transcription of large numbers of long non-coding RNAs. Since MYC is a ubiquitous oncoprotein, some of these long non-coding RNAs (lncRNAs) probably play a significant role in cancer. We applied CRISPRi to the identification of MYC-regulated lncRNAs that are required for MYC-driven cell proliferation in the P493-6 and RAMOS human lymphoid cell lines. We identified 320 non-coding loci that play a positive role in cell growth. Transcriptional repression of any one of these lncRNAs reduces the proliferative capacity of the cells. Selected hits were validated by RTqPCR and in CRISPRi-competition assays with individual GFP-expressing sgRNA-constructs. We also showed binding of MYC to the promoter of two candidate genes by chromatin immunoprecipitation. In the course of our studies, we discovered that the repressor domain SID derived from the MXD1 protein is highly effective in P493-6 and RAMOS cells in terms of the number of guides depleted in library screening and the extent of the induced transcriptional repression. In the cell lines used, it is superior to the KRAB repressor domain which serves routinely as transcriptional repressor domain in CRISPRi. The SID transcriptional repressor domain is effective as a fusion to the MS2 aptamer binding protein MCP allowing the construction of a doxycycline regulatable CRISPRi-system that allows controlled repression of targeted genes and will facilitate the functional analysis of growth-promoting lncRNAs.
Project description:MYC controls the transcription of large numbers of long noncoding RNAs (lncRNAs). Since MYC is a ubiquitous oncoprotein, some of these lncRNAs probably play a significant role in cancer. We applied CRISPR interference (CRISPRi) to the identification of MYC-regulated lncRNAs that are required for MYC-driven cell proliferation in the P493-6 and RAMOS human lymphoid cell lines. We identified 320 noncoding loci that play positive roles in cell growth. Transcriptional repression of any one of these lncRNAs reduces the proliferative capacity of the cells. Selected hits were validated by RT-qPCR and in CRISPRi competition assays with individual GFP-expressing sgRNA constructs. We also showed binding of MYC to the promoter of two candidate genes by chromatin immunoprecipitation. In the course of our studies, we discovered that the repressor domain SID (SIN3-interacting domain) derived from the MXD1 protein is highly effective in P493-6 and RAMOS cells in terms of the number of guides depleted in library screening and the extent of the induced transcriptional repression. In the cell lines used, SID is superior to the KRAB repressor domain, which serves routinely as a transcriptional repressor domain in CRISPRi. The SID transcriptional repressor domain is effective as a fusion to the MS2 aptamer binding protein MCP, allowing the construction of a doxycycline-regulatable CRISPRi system that allows controlled repression of targeted genes and will facilitate the functional analysis of growth-promoting lncRNAs.
Project description:The present study reveals LMYC and MXD1 as novel regulators of a transcriptional program that is modulated during the maturation of Batf3-dependent dendritic cells (also known as type I classical dendritic cells or cDC1s). We used microarray analysis with ERCC spike in controls to determine the transcriptional effects of MYCL and MXD1 deficiency at steady state and after activation with poly IC. Mycl-deficient mice are available from Jackson laboratories as B6.129S6(C)-Mycltm1.1Kmm/J. Mxd1-/- mice were provided by R. Eisenman.
Project description:Vitamin D signaling regulates cell proliferation and differentiation, and epidemiological data suggest that it functions as a cancer chemopreventive agent, although the underlying mechanisms are poorly understood. Vitamin D signaling can suppress expression of genes regulated by c-MYC, a transcription factor that controls epidermal differentiation and cell proliferation and whose activity is frequently elevated in cancer. We show through cell- and animal-based studies and mathematical modeling that hormonal 1,25-dihydroxyvitamin D (1,25D) and the vitamin D receptor (VDR) profoundly alter, through multiple mechanisms, the balance in function of c-MYC and its antagonist the transcriptional repressor MAD1/MXD1. 1,25D inhibited transcription of c-MYC-regulated genes in vitro, and topical 1,25D suppressed expression of c-MYC and its target setd8 in mouse skin, whereas MXD1 levels increased. 1,25D inhibited MYC gene expression and accelerated its protein turnover. In contrast, it enhanced MXD1 expression and stability, dramatically altering ratios of DNA-bound c-MYC and MXD1. Remarkably, F-box protein FBW7, an E3-ubiquitin ligase, controlled stability of both arms of the c-MYC/MXD1 push-pull network, and FBW7 ablation attenuated 1,25D regulation of c-MYC and MXD1 turnover. Additionally, c-MYC expression increased upon VDR knockdown, an effect abrogated by ablation of MYC regulator ?-catenin. c-MYC levels were widely elevated in vdr(-/-) mice, including in intestinal epithelium, where hyperproliferation has been reported, and in skin epithelia, where phenotypes of VDR-deficient mice and those overexpressing epidermal c-MYC are similar. Thus, 1,25D and the VDR regulate the c-MYC/MXD1 network to suppress c-MYC function, providing a molecular basis for cancer preventive actions of vitamin D.
Project description:Herpesviruses rely on host cell transcription and translation machineries for replication. Viral proteins thus function to redirect multiple cellular proteins for viral replication. In herpesvirus replicating cells, host cell gene transcription is frequently down-regulated because important transcriptional apparatuses are appropriated by viral transcription factors. Here we show that an evolutionally-shaped viral protein sequence is a great starting material for unique drug development to modulate cellular transcription. Cellular c-Myc protein (MYC) is overexpressed in over 70% of all types of cancer cells and therefore a very attractive target to control cancer cell growth. We identified a small functional peptide derived from the Kaposi's sarcoma-associated herpesvirus transactivator (K-Rta), which strongly attenuates MYC expression, reduces cell proliferation, and selectively kills cancer cells in both tissue culture and a xenograft tumor mouse model. Mechanistically, the peptide blocks promoter-enhancer interactions by preventing coactivator complex consisting of Nuclear receptor coactivator 2, p300, and SWI/SNF proteins from engaging the MYC promoter in leukemia cells. Target gene profiling with SLAM-seq suggests that the viral peptide attenuates MYC expression through a mechanism likely different from that of BET bromodomain inhibitors. Furthermore, fusing the 13 amino acids peptide with humanized anti-CD22 single chain armed the antibody drug with cell killing ability, and inhibited cell growth in soft agar. Our studies thus demonstrate the utility of the peptide sequence as a therapeutics module, which may be used to modulate MYC activity in a cell type-specific manner.
Project description:Herpesviruses rely on host cell transcription and translation machineries for replication. Viral proteins thus function to redirect multiple cellular proteins for viral replication. In herpesvirus replicating cells, host cell gene transcription is frequently down-regulated because important transcriptional apparatuses are appropriated by viral transcription factors. Here we show that an evolutionally-shaped viral protein sequence is a great starting material for unique drug development to modulate cellular transcription. Cellular c-Myc protein (MYC) is overexpressed in over 70% of all types of cancer cells and therefore a very attractive target to control cancer cell growth. We identified a small functional peptide derived from the Kaposi's sarcoma-associated herpesvirus transactivator (K-Rta), which strongly attenuates MYC expression, reduces cell proliferation, and selectively kills cancer cells in both tissue culture and a xenograft tumor mouse model. Mechanistically, the peptide blocks promoter-enhancer interactions by preventing coactivator complex consisting of Nuclear receptor coactivator 2, p300, and SWI/SNF proteins from engaging the MYC promoter in leukemia cells. Target gene profiling with SLAM-seq suggests that the viral peptide attenuates MYC expression through a mechanism likely different from that of BET bromodomain inhibitors. Furthermore, fusing the 13 amino acids peptide with humanized anti-CD22 single chain armed the antibody drug with cell killing ability, and inhibited cell growth in soft agar. Our studies thus demonstrate the utility of the peptide sequence as a therapeutics module, which may be used to modulate MYC activity in a cell type-specific manner.