scholarly journals BRG1 Controls the Activity of the Retinoblastoma Protein via Regulation of p21CIP1/WAF1/SDI

2004 ◽  
Vol 24 (3) ◽  
pp. 1188-1199 ◽  
Author(s):  
Hyeog Kang ◽  
Kairong Cui ◽  
Keji Zhao
Keyword(s):  
Transcriptional Repression ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Cellular Proliferation ◽  
Growth Arrest ◽  
Retinoblastoma Protein ◽  
Direct Interaction ◽  
Physical Interaction ◽  
Cdk Inhibitor ◽  
Regulation Of Cell Cycle

ABSTRACT The ubiquitous mammalian chromatin-remodeling SWI/SNF-like BAF complexes play critical roles in tumorigenesis. It was suggested that the direct interaction of BRG1 with the retinoblastoma protein pRB is required for regulation of cell cycle progression by pRB. We present evidence that the BRG1-containing complexes regulate the expression of the cdk inhibitor p21CIP1/WAF1/SDI. Furthermore, we show that the physical interaction between BRG1 and pRB is not required for induction of cell growth arrest and transcriptional repression of E2F target genes by pRB. Instead, BRG1 activates pRB by inducing its hypophosphorylation through up-regulation of the cdk inhibitor p21. The hypophosphorylation of pRB is reinforced by down-regulation of critical components, including cdk2, cyclin E, and cyclin D, in the pRB regulatory network. We demonstrate that up-regulation of p21 by BRG1 is necessary to induce formation of flat cells, growth arrest, and finally, cell senescence. Our results suggest that the BRG1-containing complexes control cellular proliferation and senescence by modulating the pRB pathway via multiple mechanisms.

scholarly journals Gfi1 Upregulates c-Myc Expression and Promotes c-Myc-Driven Cell Proliferation

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3769-3769
Author(s):  
Yangyang Zhang ◽  
Fan Dong
Keyword(s):  
Cell Proliferation ◽  
Transcription Factor ◽  
Transcriptional Repression ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Protein Levels ◽  
Enhanced Expression ◽  
Ubiquitin Proteasome

Gfi1 is a zinc-finger transcriptional repressor that plays an important role in hematopoiesis. When aberrantly activated, Gfi1 may function as a weak oncoprotein in the lymphoid system, but collaborate strongly with c-Myc in lymphomagenesis. c-Myc is a transcription factor that is frequently activated in human cancers including leukemia and lymphoma mainly due to its overexpression as a result of gene amplifications and chromosomal translocations. c-Myc overexpression may also result from stabilization of c-Myc protein, which is highly unstable and rapidly degraded through the ubiquitin-proteasome pathway. The mechanism by which Gfi1 collaborates with c-Myc in lymphomagenesis is incompletely understood. c-Myc activates gene expression by forming a heterodimeric complex with the partner protein Max, but may also repress target genes through interaction with transcription factor Miz-1. We previously showed that Gfi1 indirectly interacts with c-Myc through Miz-1 and collaborates with c-Myc to repress CDK inhibitors p21Cip1 and p15Ink4B. In this study, we show that Gfi1 augmented the level of c-Myc protein transiently expressed in Hela cells and the levels of MycER fusion protein stably expressed in the mouse pro-B Ba/F3 and myeloid 32D cells. The C-terminal ZF domains of Gfi1, but not its transcriptional repression and DNA binding activities, were required for c-Myc upregulation. Notably, although Miz-1 has been shown to stabilize c-Myc protein, the expression of c-Myc V394D mutant, which is defective in Miz-1 interaction, was still upregulated by Gfi1, suggesting that Gfi1-mediated c-Myc upregulation was independent of Miz-1 interaction. We further show that Gfi1 overexpression led to reduced polyubiquitination and increased stability of c-Myc protein. Interestingly, the levels of endogenous c-Myc mRNA and protein were augmented upon induction of Gfi1 expression in Ba/F3 and Burkitt lymphoma Ramos cells transduced with the doxycycline-inducible Gfi1 lentiviral construct, but reduced in Gfi1-knocked down human leukemic HL60 and U937 cells. Additionally, targeted deletion of Gfi1 resulted in reduced c-Myc expression in mouse lineage negative bone marrow cells, which was associated with a decline in the expression of c-Myc-activated target genes. The oncogenic potential of Myc derives from its ability to stimulate cell proliferation. Our results demonstrate that inducible expression of Gfi1 in Ba/F3 cells expressing MycER promoted Myc-driven cell cycle progression and proliferation. Thus, in addition to its role in c-Myc-mediated transcriptional repression, Gfi1 upregulates c-Myc expression at both mRNA and protein levels, leading to enhanced expression of c-Myc-activated genes and augmented cell proliferation driven by c-Myc. Together, these data may reveal a novel mechanism by which Gfi1 collaborates with c-Myc in lymphomagenesis. Disclosures No relevant conflicts of interest to declare.

E2f4 regulates fetal erythropoiesis through the promotion of cellular proliferation

Blood ◽  
2006 ◽  
Vol 108 (3) ◽  
pp. 886-895 ◽  
Author(s):  
Kathryn M. Kinross ◽  
Allison J. Clark ◽  
Rosa M. Iazzolino ◽  
Patrick Orson Humbert
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Cellular Proliferation ◽  
Cell Cycle Control ◽  
Macrocytic Anemia ◽  
Cycle Progression ◽  
Promote Cell Cycle Progression ◽  
Regulation Of Cell Cycle ◽  
Fetal Erythropoiesis

Abstract The E2F proteins are major regulators of the transcriptional program required to coordinate cell cycle progression and exit. In particular, E2f4 has been proposed to be the principal family member responsible for the regulation of cell cycle exit chiefly through its transcriptional repressive properties. We have previously shown that E2f4–/– mice display a marked macrocytic anemia implicating E2f4 in the regulation of erythropoiesis. However, these studies could not distinguish whether E2f4 was required for differentiation, survival, or proliferation control. Here, we describe a novel function for E2f4 in the promotion of erythroid proliferation. We show that loss of E2f4 results in an impaired expansion of the fetal erythroid compartment in vivo that is associated with impaired cell cycle progression and decreased erythroid proliferation. Consistent with these observations, cDNA microarray analysis reveals cell cycle control genes as one of the major class of genes down-regulated in E2f4–/– FLs, and we provide evidence that E2f4 may directly regulate the transcriptional expression of a number of these genes. We conclude that the macrocytic anemia of E2f4–/– mice results primarily from impaired cellular proliferation and that the major role of E2f4 in fetal erythropoiesis is to promote cell cycle progression and cellular proliferation.

scholarly journals Cell Fate Determination Factor DACH1 Inhibits c-Jun–induced Contact-independent Growth

2007 ◽  
Vol 18 (3) ◽  
pp. 755-767 ◽  
Author(s):  
Kongming Wu ◽  
Manran Liu ◽  
Anping Li ◽  
Howard Donninger ◽  
Mahadev Rao ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Cell Fate ◽  
Transcriptional Repression ◽  
Target Genes ◽  
Cellular Proliferation ◽  
Cell Fate Determination ◽  
Fate Determination ◽  
Multiple Context ◽  
Mediated Contact ◽  
Inhibition Of Dna Synthesis

The cell fate determination factor DACH1 plays a key role in cellular differentiation in metazoans. DACH1 is engaged in multiple context-dependent complexes that activate or repress transcription. DACH1 can be recruited to DNA via the Six1/Eya bipartite transcription (DNA binding/coactivator) complex. c-Jun is a critical component of the activator protein (AP)-1 transcription factor complex and can promote contact-independent growth. Herein, DACH1 inhibited c-Jun–induced DNA synthesis and cellular proliferation. Excision of c-Jun with Cre recombinase, in c-junf1/f1 3T3 cells, abrogated DACH1-mediated inhibition of DNA synthesis. c-Jun expression rescued DACH1-mediated inhibition of cellular proliferation. DACH1 inhibited induction of c-Jun by physiological stimuli and repressed c-jun target genes (cyclin A, β-PAK, and stathmin). DACH1 bound c-Jun and inhibited AP-1 transcriptional activity. c-jun and c-fos were transcriptionally repressed by DACH1, requiring the conserved N-terminal (dac and ski/sno [DS]) domain. c-fos transcriptional repression by DACH1 requires the SRF site of the c-fos promoter. DACH1 inhibited c-Jun transactivation through the δ domain of c-Jun. DACH1 coprecipitated the histone deacetylase proteins (HDAC1, HDAC2, and NCoR), providing a mechanism by which DACH1 represses c-Jun activity through the conserved δ domain. An oncogenic v-Jun deleted of the δ domain was resistant to DACH1 repression. Collectively, these studies demonstrate a novel mechanism by which DACH1 blocks c-Jun-mediated contact-independent growth through repressing the c-Jun δ domain.

scholarly journals Characterization and gene structure of a novel retinoblastoma-protein-associated protein similar to the transcription regulator TFII-I

2000 ◽  
Vol 345 (3) ◽  
pp. 749-757 ◽  
Author(s):  
Xiumin YAN ◽  
Xiangshan ZHAO ◽  
Min QIAN ◽  
Ning GUO ◽  
Xiaohua GONG ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Retinoblastoma Protein ◽  
Direct Interaction ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Amino Acid Residues ◽  
Transcription Regulator ◽  
Neurodevelopmental Disease

Retinoblastoma protein (Rb) is an important regulator of vertebrate cell cycle and development. It functions through a direct interaction with protein factors involved in cell cycle progression and differentiation. In the present study we characterized a novel Rb-associated protein, Cream1, which bound to Rb specifically through a C-terminal region. Cream1 contained 959 amino acid residues and migrated as a protein of approx. 120 kDa on SDS/PAGE. It was a widely expressed nuclear protein with a nuclear localization signal resembling that of the large T antigen of simian virus 40. Its primary sequence was characteristic of five direct repeats that were similar to, but distinct from, those of TFII-I, a multifunctional transcription regulator. Three additional regions were also highly conserved in both proteins. Cream1 exhibited an activation activity that was attributed to its N-terminal portion when assayed in yeast. Its relationship with the muscle-enhancer-binding protein MusTRD1 further suggests a role in regulating gene expression. The structural gene, CREAM1, contained 27 exons and spanned more than 150 kb. It was located at human chromosome 7q11.23 in a region deleted for Williams' syndrome, a neurodevelopmental disease with multisystem abnormalities, implying its involvement in certain disorders. Taken together, our results suggest that Cream1 might serve as a positive transcription regulator under the control of Rb.

scholarly journals Retinoblastoma Protein Transcriptional Repression through Histone Deacetylation of a Single Nucleosome

2002 ◽  
Vol 22 (3) ◽  
pp. 856-865 ◽  
Author(s):  
Ashby J. Morrison ◽  
Claude Sardet ◽  
Rafael E. Herrera
Keyword(s):  
Histone Deacetylase ◽  
Transcriptional Repression ◽  
Cell Cycle Progression ◽  
Cyclin E ◽  
Retinoblastoma Protein ◽  
Histone Deacetylation ◽  
Cycle Progression ◽  
Histone Deacetylase 1 ◽  
Thiol Reactivity

ABSTRACT The retinoblastoma protein, pRb, controls transcription through recruitment of histone deacetylase to particular E2F-responsive genes. We determined the acetylation level of individual nucleosomes present in the cyclin E promoter of RB +/+ and RB −/− mouse embryo fibroblasts. We also determined the effects of pRb on nucleosomal conformation by examining the thiol reactivity of histone H3 of individual nucleosomes. We found that pRb represses the cyclin E promoter through histone deacetylation of a single nucleosome, to which it and histone deacetylase 1 bind. In addition, the conformation of this nucleosome is modulated by pRb-directed histone deacetylase activity. Thus, the repressive role of pRb in cyclin E transcription and therefore cell cycle progression can be mapped to its control of the acetylation status and conformation of a single nucleosome.

scholarly journals Cyclin D3 Promotes Adipogenesis through Activation of Peroxisome Proliferator-Activated Receptor γ

2005 ◽  
Vol 25 (22) ◽  
pp. 9985-9995 ◽  
Author(s):  
David A. Sarruf ◽  
Irena Iankova ◽  
Anna Abella ◽  
Said Assou ◽  
Stéphanie Miard ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Nuclear Receptor ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Direct Interaction ◽  
Mitotic Division ◽  
Cyclin D3 ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Diet Induced Obesity

ABSTRACT In addition to their role in cell cycle progression, new data reveal an emerging role of D-type cyclins in transcriptional regulation and cellular differentiation processes. Using 3T3-L1 cell lines to study adipogenesis, we observed an up-regulation of cyclin D3 expression throughout the differentiation process. Surprisingly, cyclin D3 was only minimally expressed during the initial stages of adipogenesis, when mitotic division is prevalent. This seemingly paradoxical expression led us to investigate a potential cell cycle-independent role for cyclin D3 during adipogenesis. We show here a direct interaction between cyclin D3 and the nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ). Our experiments reveal cyclin D3 acts as a ligand-dependent PPARγ coactivator, which, together with its cyclin-dependent kinase partner, phosphorylates the A-B domain of the nuclear receptor. Overexpression and knockdown studies with cyclin D3 had marked effects on PPARγ activity and subsequently on adipogenesis. Chromatin immunoprecipitation assays confirm the participation of cyclin D3 in the regulation of PPARγ target genes. We show that cyclin D3 mutant mice are protected from diet-induced obesity, display smaller adipocytes, have reduced adipogenic gene expression, and are insulin sensitive. Our results indicate that cyclin D3 is an important factor governing adipogenesis and obesity.

Epigenetic Regulation of Cell Cycle-Promoting Genes By Ikaros and HDAC1 in Acute Lymphoblastic Leukemia

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3571-3571
Author(s):  
Sunil Muthusami ◽  
Chunhua Song ◽  
Xiaokang Pan ◽  
Chandrika S. Gowda ◽  
Kimberly J Payne ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromatin Remodeling ◽  
Transcriptional Repression ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Lymphoblastic Leukemia ◽  
Promoter Regions ◽  
Cycle Progression ◽  
Repressive Chromatin

Abstract B-cell acute lymphoblastic leukemia (B-ALL) is the most common childhood leukemia. Expression profiling has identified IKZF1 (Ikaros) as a major tumor suppressor in B-ALL and established reduced Ikaros function as a poor prognostic marker for this disease. Ikaros regulates expression of its target genes via chromatin remodeling. In vivo, Ikaros can form a complex with histone deacetylases HDAC1 and/or HDAC2 as well as the NuRD chromatin remodeling complex. The mechanisms by which Ikaros exerts its tumor suppressor function and regulates gene expression in B-ALL are unknown. Here we report the use of chromatin immunoprecipitation coupled with next generation sequencing (ChIP-SEQ) to identify genes that are regulated by Ikaros in vivo and to determine the role of Ikaros in chromatin remodeling in B-ALL. Results reveal that Ikaros binds to the promoter regions of a large number of genes that are critical for cell cycle progression. These include CDC2, CDC16, CDC25A, ANAPC1, and ANAPC7. Overexpression of Ikaros in leukemia cells resulted in transcriptional repression of Ikaros target genes. Results from luciferase reporter assays performed using the respective promoters of Ikaros target genes support a role for Ikaros as a transcriptional repressor of these genes. Downregulation of Ikaros by siRNA resulted in increased expression of Ikaros target genes that control cell cycle progression. These results suggest that Ikaros functions as a negative regulator of cell cycle progression by repressing transcription of cell cycle-promoting genes. Next, we studied how Ikaros binding affects the epigenetic signature at promoters of Ikaros target genes. Global epigenetic mapping showed that Ikaros binding at the promoter region of cell cycle-promoting genes is associated with the formation of one of two types of repressive epigenetic marks – either H3K27me3 or H3K9me3. While these epigenetic marks were mutually exclusive, they were both associated with the loss of H3K9 acetylation and transcriptional repression. Serial qChIP assays spanning promoters of the Ikaros target genes revealed that the presence of H3K27me3 is associated with Ikaros and HDAC1 binding, while the H3K9me3 modification is associated with Ikaros binding and the absence of HDAC1. ChIP-SEQ analysis of HDAC1 global genomic binding demonstrated that over 80% of H3K27me3 modifications at promoter regions are associated with HDAC1 binding at surrounding sites. The treatment of leukemia cells with the histone deacetylase inhibitor – trichostatin (TSA) resulted in a severe reduction of global levels of H3K27me3, as evidenced by Wesern blot. These data suggest that HDAC1 activity in leukemia is essential for the formation of repressive chromatin that is characterized by the presence of H3K27me3. Our data suggest that Ikaros binding at the promoters of its target genes can result in the formation of repressive chromatin by two distinct mechanisms: 1) direct Ikaros binding resulting in increased H3K9me3 or 2) Ikaros recruitment of HDAC1 with increased H3K27me3 modifications. These data suggest distinct mechanisms for the regulation of chromatin remodeling and target gene expression by Ikaros alone, and Ikaros in complex with HDAC1. In conclusion, the presented data suggest that HDAC1 has a key role in regulating cell cycle progression and proliferation in B-ALL. Our results identify novel, Ikaros-mediated mechanisms of epigenetic regulation that contribute to tumor suppression in leukemia. Supported by National Institutes of Health R01 HL095120, and the Four Diamonds Fund Endowment. Disclosures No relevant conflicts of interest to declare.

scholarly journals ZBP-89 Promotes Growth Arrest through Stabilization of p53

2001 ◽  
Vol 21 (14) ◽  
pp. 4670-4683 ◽  
Author(s):  
Longchuan Bai ◽  
Juanita L. Merchant
Keyword(s):  
Cell Proliferation ◽  
Dna Binding ◽  
Nuclear Export ◽  
Target Genes ◽  
Kinase Inhibitor ◽  
P53 Protein ◽  
Growth Arrest ◽  
Serum Starvation ◽  
Physical Interaction ◽  
Induce Growth Arrest

ABSTRACT Transcription factor p53 can induce growth arrest and/or apoptosis in cells through activation or repression of downstream target genes. Recently, we reported that ZBP-89 cooperates with histone acetyltransferase coactivator p300 in the regulation of p21waf1, a cyclin-dependent kinase inhibitor whose associated gene is a target gene of p53. Therefore, we examined whether ZBP-89 might also inhibit cell growth by activating p53. In the present study, we demonstrate that elevated levels of ZBP-89 induce growth arrest and apoptosis in human gastrointestinal cell lines. The ZBP-89 protein accumulated within 4 h, and the p53 protein accumulated within 16 h, of serum starvation without changes in p14ARF levels, demonstrating a physiological increase in the cellular levels of these two proteins. Overexpression of ZBP-89 stabilized the p53 protein and enhanced its transcriptional activity through direct protein-protein interactions. The DNA binding and C-terminal domains of p53 and the zinc finger domain of ZBP-89 mediated the interaction. A point mutation in the p53 DNA binding domain, R273H, greatly reduced ZBP-89-mediated stabilization but not their physical interaction. Furthermore, ZBP-89 formed a complex with p53 and MDM2 and therefore did not prevent the MDM2-p53 interaction. However, heterokaryon assays demonstrated that ZBP-89 retained p53 in the nucleus. Collectively, these data indicate that ZBP-89 regulates cell proliferation in part through its ability to directly bind the p53 protein and retard its nuclear export. Our findings further our understanding of how ZBP-89 modulates cell proliferation and reveals a novel mechanism by which the p53 protein is stabilized.

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