Project description:In addition to lipid second messengers derived from the plasma membrane, increasing evidence supports the existence of nuclear lipid-dependent signaling networks. Diacylglycerol is a key second messenger, generated at the nuclear level, which is metabolized by diacylglycerol kinases (DGKs). It has been demonstrated that nuclear DGK-ζ negatively regulates cell cycle progression. The aim of this study was to identify key determinants of nuclear DGK-ζ-dependent cell cycle arrest in C2C12 mouse myoblasts. Using DNA microarrays, Real-Time RT-PCR and western blot, we demonstrated that nuclear DGK-ζ downregulated the expression of cyclin D1 and increased the expression of TIS21/BTG2/PC3, a transcriptional regulator of cyclin D1 with a strong anti-proliferative function. Overexpression of TIS21/BTG2/PC3 blocked the cells in G1 phase of the cell cycle and decreased the levels of Ser807/811 phosphorylated retinoblastoma protein, similarly to overexpression of DGK-ζ. Moreover, during myogenic differentiation of C2C12 cells, we showed an increase of TIS21/BTG2/PC3 expression and a decrease in cyclin D1 levels. siRNA downregulation of TIS21/BTG2/PC3 impaired myogenic differentiation by opposing cell cycle arrest. In summary, these data identify TIS21/BTG2/PC3 and cyclin D1 as downstream effectors of the nuclear DGK-ζ and highlight the importance of this DGK isoform in the regulation of myoblast proliferation and differentiation.
Project description:N6-methyladenosine (m6A) modification is the major post-transcriptional modification present in mammalian mRNA. m6A controls fundamental biological processes including cell proliferation, but the molecular mechanism remains unclear. Herein, we demonstrate that the m6A demethylase fat mass and obesity-associated (FTO) controls the cell cycle by targeting cyclin D1, the key regulator required for G1 phase progression. FTO silencing suppressed cyclin D1 expression and induced G1 arrest. FTO depletion upregulated cyclin D1 m6A modification, which in turn accelerated the degradation of cyclin D1 mRNA. Importantly, m6A modification of cyclin D1 oscillates in a cell cycle-dependent manner; m6A levels were suppressed during the G1 phase and enhanced during other phases. Low m6A levels during G1 were associated with nuclear translocation of FTO from the cytosol. Furthermore, nucleocytoplasmic shuttling of FTO is regulated by Casein Kinase II-mediated phosphorylation at Thr 150 of FTO. Our results highlight the role of m6A in regulating cyclin D1 mRNA stability, and add a new layer of complexity to cell cycle regulation.
Project description:Genomic aberrations of Cyclin D1 (CCND1) and CDK4 in neuroblastoma indicate that dysregulation of the G1 entry checkpoint is an important cell cycle aberration in this pediatric tumor. Here we report that analysis of Affymetrix expression data of primary neuroblastic tumors shows an extensive over-expression of Cyclin D1 and CDK4 which correlates with histological subgroups and prognosis respectively. Immunohistochemical analysis demonstrated an over-expression of Cyclin D1 in neuroblasts and a low Cyclin D1 expression in all cell types in ganglioneuroma. This suggests an involvement of G1 regulating genes in neuronal differentiation processes which we further evaluated using RNA interference against Cyclin D1 and its kinase partner CDK4 in several neuroblastoma cell lines. This resulted in pRb pathway inhibition as shown by an almost complete disappearance of CDK4 specific pRb phosphorylation; reduction of E2F transcriptional activity and a decrease of Cyclin A protein levels. The Cyclin D1 and CDK4 knock-down resulted in a significant reduction in cell proliferation, a G1 specific cell cycle arrest and moreover an extensive neuronal differentiation. Affymetrix microarray profiling of siRNA treated cells revealed a shift in expression profile towards a neuronal phenotype. Several new potential downstream players are identified. We conclude that neuroblastoma functionally depend on over-expression of G1 regulating genes to maintain their undifferentiated phenotype. Experiment Overall Design: The Cell line IMR-32 at time point 0 and transiently transfected with siRNA against GFP, Cyclin D1 and CDK4 at time point 48 hours. All experiments are biological triplicates.
Project description:Genomic aberrations of Cyclin D1 (CCND1) and CDK4 in neuroblastoma indicate that dysregulation of the G1 entry checkpoint is an important cell cycle aberration in this pediatric tumor. Here we report that analysis of Affymetrix expression data of primary neuroblastic tumors shows an extensive over-expression of Cyclin D1 and CDK4 which correlates with histological subgroups and prognosis respectively. Immunohistochemical analysis demonstrated an over-expression of Cyclin D1 in neuroblasts and a low Cyclin D1 expression in all cell types in ganglioneuroma. This suggests an involvement of G1 regulating genes in neuronal differentiation processes which we further evaluated using RNA interference against Cyclin D1 and its kinase partner CDK4 in several neuroblastoma cell lines. This resulted in pRb pathway inhibition as shown by an almost complete disappearance of CDK4 specific pRb phosphorylation; reduction of E2F transcriptional activity and a decrease of Cyclin A protein levels. The Cyclin D1 and CDK4 knock-down resulted in a significant reduction in cell proliferation, a G1 specific cell cycle arrest and moreover an extensive neuronal differentiation. Affymetrix microarray profiling of siRNA treated cells revealed a shift in expression profile towards a neuronal phenotype. Several new potential downstream players are identified. We conclude that neuroblastoma functionally depend on over-expression of G1 regulating genes to maintain their undifferentiated phenotype. Keywords: Neuroblastoma, CCND1, Cyclin D1, CDK4
Project description:Analysis of mammary glands from tet-inducible(rtTA) transgenic mice expressing cyclin D1 using Affymetrix Mouse Gene 1.0 ST GeneChip arrays. MMTV-rtTA transgenic mice (MMTV-Mouse Mammary Tumor Virus promoter) were cross-mated to cyclin D1 transgenic mice under control of tet operon. 8-week-old tetracycline-inducible cyclin D1/rtTA bi-transgenic pregnant female mice (12 days postcoitus) were treated with doxycycline through drinking water supplementation at a final concentration of 2 mg/ml. Control mice were rtTA transgenics alone and treated in the same manner. After 7 days of doxycycline treatment, the mice were sacrificed and mammary glands taken for RNA isolation. Results provide insight into the in vivo gene expression pattern regulated by cyclin D1 through acute induction. Analysis of mammary glands from MMTV-cyclin D1/WT and MMTV-cyclin D1/KE using Affymetrix Mouse 430A v2.0 GeneChip arrays. Cyclin D1 point mutant, cyclin D1/KE K112E (K112E) contains a lysine to glutamine substitution at amino acid position 112. cyclin D1. The cyclin D1/KE mutant fails to induce cyclin D1-dependent kinase activity. Female MFD1, MFD1-KE, and WT mice were monitored twice weekly, up to 760 days, for the development of palpable tumors. Those developing palpable tumors were sacrificed within a week of tumor detection. Tumors were dissected and portions snap frozen for RNA isolation. Results provide insight into the in vivo gene expression pattern regulated by cyclin D1 that is kinase independent.
Project description:Analysis of mammary glands from tet-inducible(rtTA) transgenic mice expressing cyclin D1 using Affymetrix Mouse Gene 1.0 ST GeneChip arrays. MMTV-rtTA transgenic mice (MMTV-Mouse Mammary Tumor Virus promoter) were cross-mated to cyclin D1 transgenic mice under control of tet operon. 8-week-old tetracycline-inducible cyclin D1/rtTA bi-transgenic pregnant female mice (12 days postcoitus) were treated with doxycycline through drinking water supplementation at a final concentration of 2 mg/ml. Control mice were rtTA transgenics alone and treated in the same manner. After 7 days of doxycycline treatment, the mice were sacrificed and mammary glands taken for RNA isolation. Results provide insight into the in vivo gene expression pattern regulated by cyclin D1 through acute induction. Analysis of mammary glands from MMTV-cyclin D1/WT and MMTV-cyclin D1/KE using Affymetrix Mouse 430A v2.0 GeneChip arrays. Cyclin D1 point mutant, cyclin D1/KE K112E (K112E) contains a lysine to glutamine substitution at amino acid position 112. cyclin D1. The cyclin D1/KE mutant fails to induce cyclin D1-dependent kinase activity. Female MFD1, MFD1-KE, and WT mice were monitored twice weekly, up to 760 days, for the development of palpable tumors. Those developing palpable tumors were sacrificed within a week of tumor detection. Tumors were dissected and portions snap frozen for RNA isolation. Results provide insight into the in vivo gene expression pattern regulated by cyclin D1 that is kinase independent. Two separate control mice were positive for MMTV-rtTA transgene compared to 3 separate cyclin D1/rtTA bitransgenic female mice and 3 separate cyclin D1 KE mutant/rtTA bitransgenic female mice (Mouse Gene 1.0 ST arrays). Three separate control WT FvBmice were compared to three MMTV-cyclin D1/WT and 3 MMTV-cyclin D1/KE mice (Mouse 430A v2.0 arrays).
Project description:Interferons have been ascribed to mediate antitumor effects. IRF-1 is a major target gene of interferons. It inhibits cell proliferation and oncogenic transformation. Here we show that 60% of all mRNAs deregulated by oncogenic transformation mediated by c-myc and H-ras are reverted to the expression levels of non-transformed cells by IRF-1. These include cell cycle regulating genes. Activation of IRF-1 decreases cyclin D1 expression and CDK4 kinase activity concomitant with dephosphorylation of pRb. These effects of IRF-1 are mediated by inhibition of the MEK-ERK pathway and a transcriptional repression of cyclin D1. IRF-1 mediated effects on cell cycle progression were found to be overridden by ectopic expression of cyclin D1. Ablation of cyclin D1 by RNA interference experiments prevents transformation and tumor growth in nude mice. The data demonstrate that cyclin D1 is a key target for IRF-1 mediated tumor suppressive effects. Experiment Overall Design: 3 samples were analysed, two replicates per sample. NIH3T3 cells were compared with myc/ras transformed NIH3T3 cells and with IRF1 expressing myc/ras transformed cells.
Project description:Interferons have been ascribed to mediate antitumor effects. IRF-1 is a major target gene of interferons. It inhibits cell proliferation and oncogenic transformation. Here we show that 60% of all mRNAs deregulated by oncogenic transformation mediated by c-myc and H-ras are reverted to the expression levels of non-transformed cells by IRF-1. These include cell cycle regulating genes. Activation of IRF-1 decreases cyclin D1 expression and CDK4 kinase activity concomitant with dephosphorylation of pRb. These effects of IRF-1 are mediated by inhibition of the MEK-ERK pathway and a transcriptional repression of cyclin D1. IRF-1 mediated effects on cell cycle progression were found to be overridden by ectopic expression of cyclin D1. Ablation of cyclin D1 by RNA interference experiments prevents transformation and tumor growth in nude mice. The data demonstrate that cyclin D1 is a key target for IRF-1 mediated tumor suppressive effects. Keywords: NIH3T3 cells, myc, ras, IRF-1, proliferation, transformation, G1/S cell cycle ceckpoint
Project description:Inactivation of theVHLtumor suppressor gene stabilizes HIF2a, which drives clear cell renal carcinoma (ccRCC). The HIF2ainhibitor belzutifan is approved for ccRCC treatment, butde novoand acquiredresistance are common. HIF2a, bound to ARNT, transcriptionally activates hundreds of genes. We performed genome-wide CRISPRa screens in HIF2a-dependent ccRCC lines treated with the belzutifan tool compound PT2399 to identify HIF2a-responsive genes that confer belzutifan resistance when not downregulated. Sustaining the expression of the HIF2atarget geneCCND1, encoding Cyclin D1, promoted HIF2a-independence/belzutifan resistance. This activity requires Cdk4/6 activation by Cyclin D1, but is not solely due to inhibitory phosphorylation of the canonical Cyclin D1 target, pRB. Indeed, ccRCC lines lacking all three pRB family members remained at least partially HIF2a-dependent. In this context. However, kinase-defective Cyclin D1 variants at least partially overrode belzutifan’s antiproliferative effects, suggesting that ccRCC promotion by Cyclin D1 requires the phosphorylation of pRB paralogs and one or more kinase-independent Cyclin D1 activities.
Project description:Inactivation of theVHLtumor suppressor gene stabilizes HIF2a, which drives clear cell renal carcinoma (ccRCC). The HIF2ainhibitor belzutifan is approved for ccRCC treatment, butde novoand acquiredresistance are common. HIF2a, bound to ARNT, transcriptionally activates hundreds of genes. We performed genome-wide CRISPRa screens in HIF2a-dependent ccRCC lines treated with the belzutifan tool compound PT2399 to identify HIF2a-responsive genes that confer belzutifan resistance when not downregulated. Sustaining the expression of the HIF2atarget geneCCND1, encoding Cyclin D1, promoted HIF2a-independence/belzutifan resistance. This activity requires Cdk4/6 activation by Cyclin D1, but is not solely due to inhibitory phosphorylation of the canonical Cyclin D1 target, pRB. Indeed, ccRCC lines lacking all three pRB family members remained at least partially HIF2a-dependent. In this context. However, kinase-defective Cyclin D1 variants at least partially overrode belzutifan’s antiproliferative effects, suggesting that ccRCC promotion by Cyclin D1 requires the phosphorylation of pRB paralogs and one or more kinase-independent Cyclin D1 activities.