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.

scholarly journals Essential Dosage-Dependent Functions of the Transcription Factor Yin Yang 1 in Late Embryonic Development and Cell Cycle Progression

2006 ◽  
Vol 26 (9) ◽  
pp. 3565-3581 ◽  
Author(s):  
El Bachir Affar ◽  
Frédérique Gay ◽  
Yujiang Shi ◽  
Huifei Liu ◽  
Maite Huarte ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Transcription Factor ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Eukaryotic Cell ◽  
Dependent Manner ◽  
Phenotypic Analysis ◽  
Yin Yang 1 ◽  
Yin Yang

ABSTRACT Constitutive ablation of the Yin Yang 1 (YY1) transcription factor in mice results in peri-implantation lethality. In this study, we used homologous recombination to generate knockout mice carrying yy1 alleles expressing various amounts of YY1. Phenotypic analysis of yy1 mutant embryos expressing ∼75%, ∼50%, and ∼25% of the normal complement of YY1 identified a dosage-dependent requirement for YY1 during late embryogenesis. Indeed, reduction of YY1 levels impairs embryonic growth and viability in a dose-dependent manner. Analysis of the corresponding mouse embryonic fibroblast cells also revealed a tight correlation between YY1 dosage and cell proliferation, with a complete ablation of YY1 inducing cytokinesis failure and cell cycle arrest. Consistently, RNA interference-mediated inhibition of YY1 in HeLa cells prevents cytokinesis, causes proliferative arrest, and increases cellular sensitivity to various apoptotic agents. Genome-wide expression profiling identified a plethora of YY1 target genes that have been implicated in cell growth, proliferation, cytokinesis, apoptosis, development, and differentiation, suggesting that YY1 coordinates multiple essential biological processes through a complex transcriptional network. These data not only shed new light on the molecular basis for YY1 developmental roles and cellular functions, but also provide insight into the general mechanisms controlling eukaryotic cell proliferation, apoptosis, and differentiation.

scholarly journals VprBP/DCAF1 Regulates the Degradation and Nonproteolytic Activation of the Cell Cycle Transcription Factor FoxM1

2017 ◽  
Vol 37 (13) ◽  
Author(s):  
Xianxi Wang ◽  
Anthony Arceci ◽  
Kelly Bird ◽  
Christine A. Mills ◽  
Rajarshi Choudhury ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Chromosome Instability ◽  
Vital Role ◽  
Activation Mechanism ◽  
Cycle Progression ◽  
Protein Levels ◽  
Ubiquitin System

ABSTRACT The oncogenic transcription factor FoxM1 plays a vital role in cell cycle progression, is activated in numerous human malignancies, and is linked to chromosome instability. We characterize here a cullin 4-based E3 ubiquitin ligase and its substrate receptor, VprBP/DCAF1 (CRL4VprBP), which we show regulate FoxM1 ubiquitylation and degradation. Paradoxically, we also found that the substrate receptor VprBP is a potent FoxM1 activator. VprBP depletion reduces expression of FoxM1 target genes and impairs mitotic entry, whereas ectopic VprBP expression strongly activates a FoxM1 transcriptional reporter. VprBP binding to CRL4 is reduced during mitosis, and our data suggest that VprBP activation of FoxM1 is ligase independent. This implies a nonproteolytic activation mechanism that is reminiscent of, yet distinct from, the ubiquitin-dependent transactivation of the oncoprotein Myc by other E3s. Significantly, VprBP protein levels were upregulated in high-grade serous ovarian patient tumors, where the FoxM1 signature is amplified. These data suggest that FoxM1 abundance and activity are controlled by VprBP and highlight the functional repurposing of E3 ligase substrate receptors independent of the ubiquitin system.

scholarly journals The SIN3/RPD3 Deacetylase Complex Is Essential for G2 Phase Cell Cycle Progression and Regulation of SMRTER Corepressor Levels

2002 ◽  
Vol 22 (14) ◽  
pp. 4965-4976 ◽  
Author(s):  
Lori A. Pile ◽  
Erin M. Schlag ◽  
David A. Wassarman
Keyword(s):  
Cell Cycle ◽  
Transcriptional Repression ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Phase Delay ◽  
Phase Cell ◽  
Global Changes ◽  
Cycle Progression ◽  
Protein Levels ◽  
Repression Complex

ABSTRACT The SIN3 corepressor and RPD3 histone deacetylase are components of the evolutionarily conserved SIN3/RPD3 transcriptional repression complex. Here we show that the SIN3/RPD3 complex and the corepressor SMRTER are required for Drosophila G2 phase cell cycle progression. Loss of the SIN3, but not the p55, SAP18, or SAP30, component of the SIN3/RPD3 complex by RNA interference (RNAi) causes a cell cycle delay prior to initiation of mitosis. Loss of RPD3 reduces the growth rate of cells but does not cause a distinct cell cycle defect, suggesting that cells are delayed in multiple phases of the cell cycle, including G2. Thus, the role of the SIN3/RPD3 complex in G2 phase progression appears to be independent of p55, SAP18, and SAP30. SMRTER protein levels are reduced in SIN3 and RPD3 RNAi cells, and loss of SMRTER by RNAi is sufficient to cause a G2 phase delay, demonstrating that regulation of SMRTER protein levels by the SIN3/RPD3 complex is a vital component of the transcriptional repression mechanism. Loss of SIN3 does not affect global acetylation of histones H3 and H4, suggesting that the G2 phase delay is due not to global changes in genome integrity but rather to derepression of SIN3 target genes.

scholarly journals Gfi1 upregulates c-Myc expression and promotes c-Myc-driven cell proliferation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yangyang Zhang ◽  
Fan Dong
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Dna Binding ◽  
Zinc Finger ◽  
Transcriptional Repression ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Biological Function ◽  
Transcriptional Repressor ◽  
Cycle Progression

Abstract 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 collaborates strongly with c-Myc in lymphomagenesis. The mechanism by which Gfi1 collaborates with c-Myc in lymphomagenesis is incompletely understood. We show here that Gfi1 augmented the expression of c-Myc protein in cells transfected with c-Myc expression constructs. The N-terminal SNAG domain and C-terminal ZF domains of Gfi1, but not its transcriptional repression and DNA binding activities, were required for c-Myc upregulation. 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 Gfi1 overexpression, but reduced following Gfi1 knockdown or knockout, which was associated with a decline in the expression of c-Myc-activated target genes. Consistent with its role in the regulation of c-Myc expression, Gfi1 promoted Myc-driven cell cycle progression and proliferation. Together, these data reveal a novel mechanism by which Gfi1 augments the biological function of c-Myc and may have implications for understanding the functional collaboration between Gfi1 and c-Myc in lymphomagenesis.

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 Id2 Promotes Apoptosis by a Novel Mechanism Independent of Dimerization to Basic Helix-Loop-Helix Factors

1998 ◽  
Vol 18 (9) ◽  
pp. 5435-5444 ◽  
Author(s):  
Monica Florio ◽  
Maria-Clemencia Hernandez ◽  
Hui Yang ◽  
Hui-Kuo Shu ◽  
John L. Cleveland ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Death ◽  
Target Genes ◽  
Specific Binding ◽  
Helix Loop Helix ◽  
Cell Death Pathway ◽  
Id Proteins ◽  
Enhanced Expression ◽  
Positive Regulators ◽  
Hlh Transcription Factors

ABSTRACT Members of the helix-loop-helix (HLH) family of Id proteins have demonstrated roles in the regulation of differentiation and cell proliferation. Id proteins inhibit differentiation by HLH-mediated heterodimerization with basic HLH transcription factors. This blocks their sequence-specific binding to DNA and activation of target genes that are often expressed in a tissue-specific manner. Id proteins can also act as positive regulators of cell proliferation. The different mechanisms proposed for Id-mediated promotion of entry into S phase also involve HLH-mediated interactions affecting regulators of the G1/S transition. We have found that Id2 augments apoptosis in both interleukin-3 (IL-3)-dependent 32D.3 myeloid progenitors and U2OS osteosarcoma cells. We could not detect a similar activity for Id3. In contrast to the effects of Id2 on differentiation and cell proliferation, Id2-mediated apoptosis is independent of HLH-mediated dimerization. The ability of Id2 to promote cell death resides in its N-terminal region and is associated with the enhanced expression of a known component of the programmed cell death pathway, the proapoptotic gene BAX.

Interaction of the transforming growth factor-β and Notch signaling pathways in the regulation of granulosa cell proliferation

2016 ◽  
Vol 28 (12) ◽  
pp. 1873 ◽  
Author(s):  
Xiao-Feng Sun ◽  
Xing-Hong Sun ◽  
Shun-Feng Cheng ◽  
Jun-Jie Wang ◽  
Yan-Ni Feng ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Transcription Factor ◽  
Growth Factor ◽  
Granulosa Cell ◽  
Target Genes ◽  
Transforming Growth Factor ◽  
Notch Pathway ◽  
Transforming Growth Factor Β ◽  
Notch Signalling ◽  
Signalling Pathways

The Notch and transforming growth factor (TGF)-β signalling pathways play an important role in granulosa cell proliferation. However, the mechanisms underlying the cross-talk between these two signalling pathways are unknown. Herein we demonstrated a functional synergism between Notch and TGF-β signalling in the regulation of preantral granulosa cell (PAGC) proliferation. Activation of TGF-β signalling increased hairy/enhancer-of-split related with YRPW motif 2 gene (Hey2) expression (one of the target genes of the Notch pathway) in PAGCs, and suppression of TGF-β signalling by Smad3 knockdown reduced Hey2 expression. Inhibition of the proliferation of PAGCs by N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butylester (DAPT), an inhibitor of Notch signalling, was rescued by both the addition of ActA and overexpression of Smad3, indicating an interaction between the TGF-β and Notch signalling pathways. Co-immunoprecipitation (CoIP) and chromatin immunoprecipitation (ChIP) assays were performed to identify the point of interaction between the two signalling pathways. CoIP showed direct protein–protein interaction between Smad3 and Notch2 intracellular domain (NICD2), whereas ChIP showed that Smad3 could be recruited to the promoter regions of Notch target genes as a transcription factor. Therefore, the findings of the present study support the idea that nuclear Smad3 protein can integrate with NICD2 to form a complex that acts as a transcription factor to bind specific DNA motifs in Notch target genes, such as Hey1 and Hey2, and thus participates in the transcriptional regulation of Notch target genes, as well as regulation of the proliferation of PAGCs.

Gfi1 ubiquitination and proteasomal degradation is inhibited by the ubiquitin ligase Triad1

Blood ◽  
2007 ◽  
Vol 110 (9) ◽  
pp. 3128-3135 ◽  
Author(s):  
Jurgen A. F. Marteijn ◽  
Laurens T. van der Meer ◽  
Liesbeth van Emst ◽  
Simon van Reijmersdal ◽  
Willemijn Wissink ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Ubiquitin Ligase ◽  
Ubiquitin Proteasome System ◽  
Proteasomal Degradation ◽  
Binding Domain ◽  
U937 Cells ◽  
Dna Binding Domain ◽  
Protein Levels ◽  
Ubiquitin Ligase Activity ◽  
Ubiquitin Proteasome

Abstract Growth factor independence 1 (Gfi1) is a transcriptional repressor essential for the function and development of many different hematopoietic lineages. The Gfi1 protein expression is regulated by the ubiquitin-proteasome system. In granulocytes, Gfi1 is rapidly degraded by the proteasome, while it is more stable in monocytes. How the ubiquitination and degradation of Gfi1 is regulated is unclear. Here, we show that the ubiquitin ligase Triad1 interacts with the DNA-binding domain of Gfi1. Unexpectedly, we found that Triad1 inhibited Gfi1 ubiquitination, resulting in a prolonged half-life. Down-regulation of endogenous Triad1 by siRNAs resulted in increased Gfi1 ubiquitination. In U937 cells, Triad1 caused an increase in endogenous Gfi1 protein levels and slowed cell proliferation in a similar manner when Gfi1 itself was expressed. A Triad1 mutant that lacks the Gfi1-binding domain did not affect Gfi1 levels and proliferation. Because neither proteasome-ubiquitin nor Triad1 ubiquitin ligase activity was required for the inhibition of Gfi1 ubiquitination, these data suggest that Triad1 competes for Gfi1 binding with as yet to be identified E3 ubiquitin ligases that do mark Gfi1 for proteasomal degradation. The finetuning of Gfi1 protein levels regulated by Triad1 defines an unexpected role for this protein in hematopoiesis.

scholarly journals Smarcd1 Inhibits the Malignant Phenotypes of Human Glioblastoma Cells via Crosstalk with Notch1

2020 ◽  
Author(s):  
Yihao Zhu ◽  
Handong Wang ◽  
Maoxing Fei ◽  
Ting Tang ◽  
Wenhao Niu ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Lines ◽  
High Grade Glioma ◽  
Glioblastoma Cell ◽  
Glioblastoma Cells ◽  
Human Glioblastoma ◽  
Protein Levels ◽  
Enhanced Expression ◽  
Human Glioblastoma Cells ◽  
Glioblastoma Cell Lines

AbstractSmarcd1 is a component of an evolutionary conserved chromatin remodeling complex—SWI/SNF, which is involved in transcription factor recruitment, DNA replication, recombination, and repair. Suppression of the SWI/SNF complex required for cellular differentiation and gene regulation may be inducible for cell proliferation and tumorigenicity. However, the inhibitory role of Smarcd1 in human glioblastoma cells has not been well illustrated. Both U87 and U251 human glioblastoma cell lines were employed in the present study. The lentivirus-mediated gene knockdown and overexpression approach was conducted to determine the function of Smarcd1. The protein levels were tested by western blot, and the relative mRNA contents were detected by quantitative real-time PCR. Cell viability was tested by CCK-8 and colony-forming assay. Transwell assays were utilized to evaluate the motility and invasive ability. Flow cytometry was employed to analyze cell cycle and apoptosis. SPSS software was used for statistical analysis. Low expression of Smarcd1 was observed in glioblastoma cell lines and in patients with high-grade glioma. Importantly, the depletion of Smarcd1 promoted cell proliferation, invasion, and chemoresistance, whereas enhanced expression of Smarcd1 inhibited tumor-malignant phenotypes. Mechanistic research demonstrated that overexpression of Smarcd1 decreased the expression of Notch1, while knockdown of Notch1 increased the expression of Smarcd1 through Hes1 suppression. Hence, the crosstalk between Smarcd1 and Notch1, which formed a feedback loop, was crucial in regulation of glioblastoma malignant phenotypes. Furthermore, targeting Smarcd1 could be a potential strategy for human glioblastoma treatment.

scholarly journals Lentivirus-Mediated siRNA Targeting ER-αInhibits Tumorigenesis and Induces Apoptosis in Hepatocarcinoma Cells

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Ping Jiang ◽  
Jun Cao ◽  
Wen-Hui Bai
Keyword(s):  
Cell Proliferation ◽  
Cell Cycle Progression ◽  
Dependent Manner ◽  
Gene Therapy Approach ◽  
Protein Levels ◽  
Human Liver Cancer ◽  
Hepatocarcinoma Cells ◽  
Interfering Rna ◽  
Hcc Cells

Background and Objectives. Estrogen receptor-α(ER-α) plays important roles in hepatocarcinogenesis. Recent studies have shown that ER-αcould lead to cell cycle progression or inhibition of apoptosis. To better understand the role of ER-α, RNA interference (RNAi) was used to inhibit ER-αexpression in the human hepatocellular carcinoma (HCC) cells.Methods. Lentivirus-mediated ER-αsmall interfering RNA (siRNA) was transfected into HCC cells Hep3B. ER-αexpression was monitored by real-time polymerase chain reaction (PCR) and western blot. Cell proliferation, apoptosis, and invasion were examined by methyl thiazol tetrazolium (MTT), flow cytometry (FCM), and invasion assay, respectively.Results. ER-αsiRNA efficiently downregulated the expression of ER-αin Hep3B cells at both mRNA and protein levels in a time-dependent manner. ER-αsiRNA also inhibited cell proliferation and reduced cell invasion (compared with other groups,P<0.05, resp.). Furthermore, knockdown of ER-αslowed down the cell population at S phase and increased the rate of apoptosis (P<0.05, resp.).Conclusion. ER-αknockdown suppressed the growth of HCC cells. Thus, ER-αmay play a very important role in carcinogenesis of HCC and its knockdown may offer a new potential gene therapy approach for human liver cancer in the future.

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