scholarly journals A Mammalian Bromodomain Protein, Brd4, Interacts with Replication Factor C and Inhibits Progression to S Phase

2002 ◽  
Vol 22 (18) ◽  
pp. 6509-6520 ◽  
Author(s):  
Tetsuo Maruyama ◽  
Andrea Farina ◽  
Anup Dey ◽  
JaeHun Cheong ◽  
Vladimir P. Bermudez ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Replication Factor C ◽  
Cycle Progression ◽  
Vitro Analysis ◽  
Factor C ◽  
In Vitro Analysis

ABSTRACT Brd4 belongs to the BET family of nuclear proteins that carry two bromodomains implicated in the interaction with chromatin. Expression of Brd4 correlates with cell growth and is induced during early G1 upon mitogenic stimuli. In the present study, we investigated the role of Brd4 in cell growth regulation. We found that ectopic expression of Brd4 in NIH 3T3 and HeLa cells inhibits cell cycle progression from G1 to S. Coimmunoprecipitation experiments showed that endogenous and transfected Brd4 interacts with replication factor C (RFC), the conserved five-subunit complex essential for DNA replication. In vitro analysis showed that Brd4 binds directly to the largest subunit, RFC-140, thereby interacting with the entire RFC. In line with the inhibitory activity seen in vivo, recombinant Brd4 inhibited RFC-dependent DNA elongation reactions in vitro. Analysis of Brd4 deletion mutants indicated that both the interaction with RFC-140 and the inhibition of entry into S phase are dependent on the second bromodomain of Brd4. Lastly, supporting the functional importance of this interaction, it was found that cotransfection with RFC-140 reduced the growth-inhibitory effect of Brd4. Taken as a whole, the present study suggests that Brd4 regulates cell cycle progression in part by interacting with RFC.

Distinct and sequential upregulation of genes regulating cell growth and cell cycle progression during hepatic ischemia-reperfusion injury

2005 ◽  
Vol 289 (4) ◽  
pp. C826-C835 ◽  
Author(s):  
Sharon Barone ◽  
Tomohisa Okaya ◽  
Steve Rudich ◽  
Snezana Petrovic ◽  
Kathy Tenrani ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cell Growth ◽  
Reperfusion Injury ◽  
Cell Cycle Progression ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Catabolic Pathway ◽  
Cycle Progression

Ischemia-reperfusion injury (IRI) in liver and other organs is manifested as an injury phase followed by recovery and resolution. Control of cell growth and proliferation is essential for recovery from the injury. We examined the expression of three related regulators of cell cycle progression in liver IRI: spermidine/spermine N-acetyltransferase (SSAT), p21 (a cyclin-dependent kinase inhibitor), and stathmin. Mice were subjected to hepatic IRI, and liver tissues were harvested at timed intervals. The expression of SSAT, the rate-limiting enzyme in the polyamine catabolic pathway, had increased fivefold 6 h after IRI and correlated with increased putrescine levels in the liver, consistent with increased SSAT enzymatic activity in IRI. The expression of p21, which is transactivated by p53, was undetectable in sham-operated animals but was heavily induced at 12 and 24 h of reperfusion and declined to undetectable baseline levels at 72 h of reperfusion. The interaction of the polyamine pathway with the p53-p21 pathway was shown in vitro, where activation of SSAT with polyamine analog or the addition of putrescine to cultured hepatocytes induced the expression of p53 and p21 and decreased cell viability. The expression of stathmin, which is under negative transcriptional regulation by p21 and controls cell proliferation and progression through mitosis, remained undetectable at 6, 12, and 24 h of reperfusion and was progressively and heavily induced at 48 and 72 h of reperfusion. Double-immunofluorescence labeling with antibodies against stathmin and PCNA, a marker of cell proliferation, demonstrated colocalization of stathmin and PCNA at 48 and 72 h of reperfusion in hepatocytes, indicating the initiation of cell proliferation. The distinct and sequential upregulation of SSAT, p21, and stathmin, along with biochemical activation of the polyamine catabolic pathway in IRI in vivo and the demonstration of p53-p21 upregulation by SSAT and putrescine in vitro, points to the important role of regulators of cell growth and cell cycle progression in the pathophysiology and/or recovery in liver IRI. The data further suggest that SSAT may play a role in the initiation of injury, whereas p21 and stathmin may be involved in the resolution and recovery after liver IRI.

scholarly journals Identification of DHX9 as a cell cycle regulated nucleolar recruitment factor for CIZ1

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Urvi Thacker ◽  
Tekle Pauzaite ◽  
James Tollitt ◽  
Maria Twardowska ◽  
Charlotte Harrison ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Zinc Finger Protein ◽  
S Phase ◽  
Cycle Progression ◽  
Inactive X Chromosome ◽  
Functional Characterisation ◽  
Interaction Partners

Abstract CIP1-interacting zinc finger protein 1 (CIZ1) is a nuclear matrix associated protein that facilitates a number of nuclear functions including initiation of DNA replication, epigenetic maintenance and associates with the inactive X-chromosome. Here, to gain more insight into the protein networks that underpin this diverse functionality, molecular panning and mass spectrometry are used to identify protein interaction partners of CIZ1, and CIZ1 replication domain (CIZ1-RD). STRING analysis of CIZ1 interaction partners identified 2 functional clusters: ribosomal subunits and nucleolar proteins including the DEAD box helicases, DHX9, DDX5 and DDX17. DHX9 shares common functions with CIZ1, including interaction with XIST long-non-coding RNA, epigenetic maintenance and regulation of DNA replication. Functional characterisation of the CIZ1-DHX9 complex showed that CIZ1-DHX9 interact in vitro and dynamically colocalise within the nucleolus from early to mid S-phase. CIZ1-DHX9 nucleolar colocalisation is dependent upon RNA polymerase I activity and is abolished by depletion of DHX9. In addition, depletion of DHX9 reduced cell cycle progression from G1 to S-phase in mouse fibroblasts. The data suggest that DHX9-CIZ1 are required for efficient cell cycle progression at the G1/S transition and that nucleolar recruitment is integral to their mechanism of action.

scholarly journals Lyn is activated during late G1 of stem-cell-factor-induced cell cycle progression in haemopoietic cells

1999 ◽  
Vol 342 (1) ◽  
pp. 163-170 ◽  
Author(s):  
Sherry MOU ◽  
Diana LINNEKIN
Keyword(s):  
Cell Cycle ◽  
Stem Cell ◽  
Family Member ◽  
Stem Cell Factor ◽  
Cell Cycle Progression ◽  
Kinetic Studies ◽  
S Phase ◽  
Cycle Progression ◽  
Haemopoietic Cells

Stem cell factor (SCF) binds the receptor tyrosine kinase c-Kit and is critical in haemopoiesis. Recently we found that the Src family member Lyn is highly expressed in SCF-responsive cells, associates with c-Kit and is activated within minutes of the addition of SCF. Here we show that SCF activates Lyn a second time, hours later, during SCF-induced cell cycle progression. In cells arrested at specific phases of the cell cycle with the drugs mimosine, aphidicolin and nocodazole, maximal Lyn kinase activity occurred in late G1 and through the G1/S transition. Similarly, kinetic studies of SCF-induced cell cycle progression found that activation of Lyn preceded the G1/S transition and was maintained into early S-phase. Activation of Lyn was paralleled by two events critical for the G1/S transition, increases in cyclin-dependent kinase 2 (Cdk2) activity and phosphorylation of the retinoblastoma gene product (Rb). Lyn was associated with Cdk2; Cdk2-associated Lyn was heavily phosphorylated on serine and threonine residues both in vitro and in situ during S-phase. Inhibition of Lyn activity with PP1 disrupted association with Cdk2 and decreased the numbers of cells entering S-phase. The degree of phosphorylation of Rb in PP1-treated cells suggested an increased number of cells arrested in the middle of G1. These findings demonstrate that SCF activates the Src family member Lyn before the G1/S transition of the cell cycle and suggest that Lyn is involved in SCF-induced cell cycle progression.

scholarly journals A Cds1-Mediated Checkpoint Protects the MBF Activator Rep2 from Ubiquitination by Anaphase-Promoting Complex/Cyclosome-Ste9 at S-Phase Arrest in Fission Yeast

2009 ◽  
Vol 29 (18) ◽  
pp. 4959-4970 ◽  
Author(s):  
Zhaoqing Chu ◽  
Majid Eshaghi ◽  
Suk Yean Poon ◽  
Jianhua Liu
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Transcriptional Activity ◽  
S Phase ◽  
Anaphase Promoting Complex ◽  
Cell Recovery ◽  
Cycle Progression ◽  
Phase Arrest ◽  
S Phase Arrest

ABSTRACT Transcription of the MluI cell cycle box (MCB) motif-containing genes at G1 phase is regulated by the MCB-binding factors (MBF) (also called DSC1) in Schizosaccharomyces pombe. Upon S-phase arrest, the MBF transcriptional activity is induced through the accumulation of the MBF activator Rep2. In this study, we show that the turnover of Rep2 is attributable to ubiquitin-mediated proteolysis. Levels of Rep2 oscillate during the cell cycle, with a peak at G1 phase, coincident with the MBF activity. Furthermore, we show that Rep2 ubiquitination requires the function of the E3 ligase anaphase-promoting complex/cyclosome (APC/C). Ste9 can be phosphorylated by the checkpoint kinase Cds1 in vitro, and its inhibition/phosphorylation at S-phase arrest is dependent on the function of Cds1. Our data indicate that the Cds1-dependent stabilization of Rep2 is achieved through the inhibition/phosphorylation of APC/C-Ste9 at the onset of S-phase arrest. Stabilization of Rep2 is important for stimulating transcription of the MBF-dependent genes to ensure a sufficient supply of proteins essential for cell recovery from S-phase arrest. We propose that oscillation of Rep2 plays a role in regulation of periodic transcription of the MBF-dependent genes during cell cycle progression.

scholarly journals Indomethacin Inhibits Cell Growth of Medullary Thyroid Carcinoma by Reducing Cell Cycle Progression into S Phase

2008 ◽  
Vol 233 (11) ◽  
pp. 1433-1440 ◽  
Author(s):  
Chisato Tomoda ◽  
Farhad Moatamed ◽  
Faramarz Naeim ◽  
Jerome M. Hershman ◽  
Masahiro Sugawara
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Thyroid Carcinoma ◽  
Medullary Thyroid Carcinoma ◽  
Cell Lines ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Cycle Progression ◽  
Medullary Thyroid ◽  
Tt Cells

Indomethacin, a non-steroidal anti-inflammatory drug (NSAID), has been reported to inhibit the growth of medullary thyroid carcinoma (MTC) cells in vitro. However, the mechanism of inhibition of MTC cell growth by indomethacin and its potency have yet to be revealed. We examined the effect of indomethacin on three different MTC cell lines (TT cells, DRO 81–1 cells and HRO 85–1 cells) and two non-MTC cells. The mechanism of indomethacin action in MTC cells was investigated by analyzing intracellular prostaglandin level, apoptosis, and cell cycle in TT cells. Indomethacin inhibited cell growth of all three MTC cell lines but not normal thyroid cells or anaplastic thyroid carcinoma cells. Indomethacin at 10 μM or greater showed a dose response inhibition of cell growth. Indomethacin at 25 μM, a putative therapeutic serum indomethacin level, showed potency similar to 100 to 200 nM sunitinib, a receptor tyrosine kinase inhibitor. To examine whether prostaglandin depletion might determine the inhibition of MTC cell growth, we created different prostaglandin E2 (PGE2) levels in TT cells using three different NSAIDs. A profound PGE2 depletion by indomethacin-ester, a potent cyclooxygenase (COX) II inhibitor, showed the least inhibition of cell growth. Indomethacin did not increase apoptosis of TT cells. Indomethacin, but not naproxen or indomethacin-ester, reduced cell cycle progression into S phase; this was unrelated to the degree of PGE2 depletion. The expression of phosphorylated retinoblastoma (pRb) protein that shifts cells from G1 to S phase was reduced after exposure to indomethacin. In conclusion, indomethacin has specific anti-tumor effect on MTC cells, probably by reducing cell cycle progression into S phase rather than by prostaglandin depletion. Since no drug therapy is currently available for MTC, indomethacin may be one of the therapeutic candidates.

scholarly journals Endothelial cells isolated from caveolin-2 knockout mice display higher proliferation rate and cell cycle progression relative to their wild-type counterparts

2010 ◽  
Vol 298 (3) ◽  
pp. C693-C701 ◽  
Author(s):  
Leike Xie ◽  
Philippe G. Frank ◽  
Michael P. Lisanti ◽  
Grzegorz Sowa
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Inhibitors ◽  
Fold Increase ◽  
S Phase ◽  
Lower Percentage ◽  
Wild Type ◽  
Cycle Progression ◽  
Molecular Events

The goal of this study was to determine whether caveolin-2 (Cav-2) is capable of controlling endothelial cell (EC) proliferation in vitro. To realize this goal, we have directly compared proliferation rates and cell cycle-associated signaling proteins between lung ECs isolated from wild-type (WT) and Cav-2 knockout (KO) mice. Using three independent proliferation assays, we have determined that Cav-2 KO ECs proliferate by ca. 2-fold faster than their WT counterparts. Cell cycle analysis by flow cytometry of propidium iodide-stained cells showed a relatively higher percentage of Cav-2 KO ECs in S and G2/M and lower percentage in Go/G1 phases of cell cycle relative to their WT counterparts. Furthermore, an over 2-fold increase in the percentage of S phase-associated Cav-2 KO relative to WT ECs was independently determined with bromodeoxyuridine incorporation assay. Mechanistically, the increase in proliferation/cell cycle progression of Cav-2 KO ECs correlated well with elevated expression levels of predominantly S phase- and G2/M phase-associated cyclin A and B1, respectively. Further mechanistic analysis of molecular events controlling cell cycle progression revealed increased level of hyperphosphorylated (inactive) form of G1 to S phase transition inhibitor, the retinoblastoma protein in hyperproliferating Cav-2 KO ECs. Conversely, the expression level of the two cyclin-dependent kinase inhibitors p16INK4 and p27Kip1 was reduced in Cav-2 KO ECs. Finally, increased phosphorylation (activation) of proproliferative extracellular signal-regulated kinase 1/2 was observed in hyperproliferating Cav-2 KO ECs. Overall, our data suggest that Cav-2 negatively regulates lung EC proliferation and cell cycle progression.

scholarly journals The lncRNA TEX41 is upregulated in pediatric B-Cells Acute Lymphoblastic Leukemia and it is necessary for leukemic cell growth

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Francesca Maria Orlandella ◽  
Giovanni Smaldone ◽  
Giuliana Salvatore ◽  
Luigi Vitagliano ◽  
Alessandra Cianflone ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Cell Growth ◽  
Cell Line ◽  
Cell Cycle Progression ◽  
Leukemic Cell ◽  
Cycle Progression ◽  
Total Rna ◽  
Expression Levels

Abstract Background Long non-coding RNAs (lncRNAs) represent a diverse class of RNAs involved in the regulation of various physiological and pathological cellular processes, including transcription, intracellular trafficking, and chromosome remodeling. LncRNAs deregulation was linked to the development and progression of various cancer types, such as acute leukemias. In this context, lncRNAs were also evaluated as a novel class of biomarkers for cancer diagnosis and prognosis. Here, we analyzed TEX41 in childhood B cell acute lymphoid leukemia (B-ALL). Methods Total RNA was extracted from pediatric B-ALL patients (at diagnosis and after induction of therapy) and from healthy subjects. Total RNA was also extracted from different leukemia cell line models. The expression level of TEX41 was evaluated by q-RT-PCR. Also, the dataset deposited by St. Jude Children’s Research Hospital was consulted. Furthermore, the silencing of TEX41 in RS4;11 cell line was obtained by 2′-Deoxy, 2′Fluroarabino Nucleic Acids (2′F-ANAs) Oligonucleotides, and the effect on cell proliferation was evaluated. Cell cycle progression and its regulators were analyzed by flow cytometry and immunoblotting. Results We exploited the St Jude Cloud database and found that TEX41 is a lncRNA primarily expressed in the case of B-ALL (n = 79) while its expression levels are low/absent for T-cell ALL (n = 25) and acute myeloid leukemia (n = 38). The association of TEX41 with B-ALL was confirmed by real-time PCR assays. TEX41 disclosed increased expression levels in bone marrow from patients with B-ALL at diagnosis, while its expression levels became low or absent when retested in Bone Marrow cells of the same patient after 1 month of induction therapy. Also, silencing experiments performed on RS4;11 cells showed that TEX41 downregulation impaired in vitro leukemic cell growth determining their arrest in the G2-M phase and the deregulation of cell cycle proteins. Conclusions Our findings highlight that TEX41 is an upregulated lncRNA in the case of B-ALL and this feature makes it a novel potential biomarker for the diagnosis of this leukemia subtype in pediatric patients. Finally, TEX41 expression seems to be critical for leukemic proliferation, indeed, silencing experiments targeting TEX41 mRNA in the RS4;11 cell line hampered in vitro cell growth and cell cycle progression, by inducing G2-M arrest as confirmed propidium iodide staining and by the upregulation of p53 and p21 proteins.

scholarly journals Cdc34 C-terminal tail phosphorylation regulates Skp1/cullin/F-box (SCF)-mediated ubiquitination and cell cycle progression

2007 ◽  
Vol 405 (3) ◽  
pp. 569-581 ◽  
Author(s):  
Martin Sadowski ◽  
Amanda Mawson ◽  
Rohan Baker ◽  
Boris Sarcevic
Keyword(s):  
Cell Cycle ◽  
Catalytic Activity ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Phosphorylation Sites ◽  
Tail Domain ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cycle Progression

The ubiquitin-conjugating enzyme Cdc34 (cell division cycle 34) plays an essential role in promoting the G1–S-phase transition of the eukaryotic cell cycle and is phosphorylated in vivo. In the present study, we investigated if phosphorylation regulates Cdc34 function. We mapped the in vivo phosphorylation sites on budding yeast Cdc34 (yCdc34; Ser207 and Ser216) and human Cdc34 (hCdc34 Ser203, Ser222 and Ser231) to serine residues in the acidic tail domain, a region that is critical for Cdc34's cell cycle function. CK2 (protein kinase CK2) phosphorylates both yCdc34 and hCdc34 on these sites in vitro. CK2-mediated phosphorylation increased yCdc34 ubiquitination activity towards the yeast Saccharomyces cerevisiae Sic1 in vitro, when assayed in the presence of its cognate SCFCdc4 E3 ligase [where SCF is Skp1 (S-phase kinase-associated protein 1)/cullin/F-box]. Similarly, mutation of the yCdc34 phosphorylation sites to alanine, aspartate or glutamate residues altered Cdc34–SCFCdc4-mediated Sic1 ubiquitination activity. Similar results were obtained when yCdc34's ubiquitination activity was assayed in the absence of SCFCdc4, indicating that phosphorylation regulates the intrinsic catalytic activity of Cdc34. To evaluate the in vivo consequences of altered Cdc34 activity, wild-type yCdc34 and the phosphosite mutants were introduced into an S. cerevisiae cdc34 deletion strain and, following synchronization in G1-phase, progression through the cell cycle was monitored. Consistent with the increased ubiquitination activity in vitro, cells expressing the phosphosite mutants with higher catalytic activity exhibited accelerated cell cycle progression and Sic1 degradation. These studies demonstrate that CK2-mediated phosphorylation of Cdc34 on the acidic tail domain stimulates Cdc34–SCFCdc4 ubiquitination activity and cell cycle progression.

scholarly journals Melatonin Improves Parthenogenetic Development of Vitrified–Warmed Mouse Oocytes Potentially by Promoting G1/S Cell Cycle Progression

2018 ◽  
Vol 19 (12) ◽  
pp. 4029 ◽  
Author(s):  
Bo Pan ◽  
Haoxuan Yang ◽  
Zhenzheng Wu ◽  
Izhar Qazi ◽  
Guoshi Liu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Subsequent Development ◽  
Blastocyst Stage ◽  
S Phase ◽  
Cycle Progression ◽  
Developmental Potential ◽  
Mouse Oocytes ◽  
Parthenogenetic Development

This study aimed to investigate the effect of melatonin on the cell cycle of parthenogenetic embryos derived from vitrified mouse metaphase II (MII) oocytes. Fresh oocytes were randomly allocated into three groups: untreated (control), or vitrified by the open-pulled straw method without (Vitrification group) or with melatonin (MT) supplementation (Vitrification + MT group). After warming, oocytes were parthenogenetically activated and cultured in vitro, then the percentage of embryos in the G1/S phase, the levels of reactive oxygen species (ROS) and glutathione (GSH), and the mRNA expression of cell cycle-related genes (P53, P21 and E2F1) in zygotes and their subsequent developmental potential in vitro were evaluated. The results showed that the vitrification/warming procedures significantly decreased the frequency of the S phase, markedly increased ROS and GSH levels and the expression of P53 and P21 genes, and decreased E2F1 expression in zygotes at the G1 stage and their subsequent development into 2-cell and blastocyst stage embryos. However, when 10−9 mol/L MT was administered for the whole duration of the experiment, the frequency of the S phase in zygotes was significantly increased, while the other indicators were also significantly improved and almost recovered to the normal levels shown in the control. Thus, MT might promote G1-to-S progression via regulation of ROS, GSH and cell cycle-related genes, potentially increasing the parthenogenetic development ability of vitrified–warmed mouse oocytes.

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