scholarly journals Productive Replication of Adeno-Associated Virus Can Occur in Human Papillomavirus Type 16 (HPV-16) Episome-Containing Keratinocytes and Is Augmented by the HPV-16 E2 Protein

2000 ◽  
Vol 74 (8) ◽  
pp. 3494-3504 ◽  
Author(s):  
Phyllis Ogston ◽  
Kenneth Raj ◽  
Peter Beard
Keyword(s):  
Cell Cycle ◽  
Human Papillomavirus ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Cycle Progression ◽  
Hpv 16 ◽  
Adeno Associated Virus ◽  
E2 Protein ◽  
Human Papillomavirus Type 16 ◽  
Productive Replication

ABSTRACT We used a sensitive assay to test whether an adeno-associated virus (AAV) productive replication cycle can occur in immortalized human keratinocytes carrying episomal human papillomavirus type 16 (HPV-16) DNA. Following transfection with cloned AAV DNA, infectious AAV was produced, and the infectivity was blocked by anti-AAV antiserum. The HPV-16 E2 protein substantially increased the yield of AAV. Other HPV early proteins did not, in our experiments, show this ability. E2 has been shown to be able to affect p53 levels and to block cell cycle progression at mitosis. We tested the effect of changes in p53 expression on AAV replication and found that large differences in the level of p53 did not alter AAV DNA replication. In extension of this, we found that cellular help for AAV in response to stress was also independent of p53. To test if a mitotic block could trigger AAV DNA replication, we treated the cells with the mitotic inhibitor nocodazole. AAV DNA replication was stimulated by the presence of nocodazole in these and a number of other cell types tested. Yields of infectious virus, however, were not increased by this treatment. We conclude that the HPV-16 E2 protein stimulates AAV multiplication in these cells and propose that this occurs independently of the effects of E2 on p53 and cell cycle progression. Since the effect of E2 was not seen in keratinocytes lacking the HPV-16 episome, we suggest that E2 can help AAV by working in concert with other HPV-16 proteins.

scholarly journals Human Papillomavirus Type 16 E7 Maintains Elevated Levels of the cdc25A Tyrosine Phosphatase during Deregulation of Cell Cycle Arrest

2002 ◽  
Vol 76 (2) ◽  
pp. 619-632 ◽  
Author(s):  
Don X. Nguyen ◽  
Thomas F. Westbrook ◽  
Dennis J. McCance
Keyword(s):  
Cell Cycle ◽  
Human Papillomavirus ◽  
Cell Cycle Arrest ◽  
Cell Cycle Progression ◽  
Tyrosine Phosphatase ◽  
Early Gene ◽  
Cycle Progression ◽  
Hpv 16 ◽  
Human Papillomavirus Type 16 ◽  
Cycle Arrest

ABSTRACT Essential to the oncogenic properties of human papillomavirus type 16 (HPV-16) are the activities encoded by the early gene product E7. HPV-16 E7 (E7.16) binds to cellular factors involved in cell cycle regulation and differentiation. These include the retinoblastoma tumor suppressor protein (Rb) and histone deacetylase (HDAC) complexes. While the biological significance of these interactions remains unclear, E7 is believed to help maintain cells in a proliferative state, thus establishing an environment that is conducive to viral replication. Most pathways that govern cell growth converge on downstream effectors. Among these is the cdc25A tyrosine phosphatase. cdc25A is required for G1/S transition, and its deregulation is associated with carcinogenesis. Considering the importance of cdc25A in cell cycle progression, it represents a relevant target for viral oncoproteins. Accordingly, the present study focuses on the putative deregulation of cdc25A by E7.16. Our results indicate that E7.16 can impede growth arrest induced during serum starvation and keratinocyte differentiation. Importantly, these E7-specific phenotypes correlate with elevated cdc25A steady-state levels. Reporter assays performed with NIH 3T3 cell lines and human keratinocytes indicate that E7 can transactivate the cdc25A promoter. In addition, transcriptional activation by E7.16 requires the distal E2F site within the cdc25A promoter. We further demonstrate that the ability of E7 to abrogate cell cycle arrest, activate cdc25A transcription, and increase cdc25A protein levels requires intact Rb and HDAC-1 binding domains. Finally, by using the cdk inhibitor roscovitine, we reveal that E7 activates the cdc25A promoter independently of cell cycle progression and cdk activity. Consequently, we propose that E7.16 can directly target cdc25A transcription and maintains cdc25A gene expression by disrupting Rb/E2F/HDAC-1 repressor complexes.

scholarly journals Disruption of the G1/S Transition in Human Papillomavirus Type 16 E7-Expressing Human Cells Is Associated with Altered Regulation of Cyclin E

1998 ◽  
Vol 72 (2) ◽  
pp. 975-985 ◽  
Author(s):  
Larry G. Martin ◽  
G. William Demers ◽  
Denise A. Galloway
Keyword(s):  
Cell Cycle ◽  
Human Papillomavirus ◽  
Cell Cycle Progression ◽  
Cyclin E ◽  
Cell Cycle Control ◽  
Cell Cycle Checkpoints ◽  
Hpv 16 ◽  
Human Papillomavirus Type 16 ◽  
E6 And E7 ◽  
Cell Cycle Machinery

ABSTRACT The development of neoplasia frequently involves inactivation of the p53 and retinoblastoma (Rb) tumor suppressor pathways and disruption of cell cycle checkpoints that monitor the integrity of replication and cell division. The human papillomavirus type 16 (HPV-16) oncoproteins, E6 and E7, have been shown to bind p53 and Rb, respectively. To further delineate the mechanisms by which E6 and E7 affect cell cycle control, we examined various aspects of the cell cycle machinery. The low-risk HPV-6 E6 and E7 proteins did not cause any significant change in the levels of cell cycle proteins analyzed. HPV-16 E6 resulted in very low levels of p53 and p21 and globally elevated cyclin-dependent kinase (CDK) activity. In contrast, HPV-16 E7 had a profound effect on several aspects of the cell cycle machinery. A number of cyclins and CDKs were elevated, and despite the elevation of the levels of at least two CDK inhibitors, p21 and p16, CDK activity was globally increased. Most strikingly, cyclin E expression was deregulated both transcriptionally and posttranscriptionally and persisted at high levels in S and G2/M. Transit through G1 was shortened by the premature activation of cyclin E-associated kinase activity. Elevation of cyclin E levels required both the CR1 and CR2 domains of E7. These data suggest that cyclin E may be a critical target of HPV-16 E7 in the disruption of G1/S cell cycle progression and that the ability of E7 to regulate cyclin E involves activities in addition to the release of E2F.

scholarly journals Regulation of Cell Division in Bacteria by Monitoring Genome Integrity and DNA Replication Status

2019 ◽  
Vol 202 (2) ◽  
Author(s):  
Peter E. Burby ◽  
Lyle A. Simmons
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Genome Instability ◽  
Sos Response ◽  
Bacterial Cells ◽  
Cycle Progression ◽  
Content Type

ABSTRACT All organisms regulate cell cycle progression by coordinating cell division with DNA replication status. In eukaryotes, DNA damage or problems with replication fork progression induce the DNA damage response (DDR), causing cyclin-dependent kinases to remain active, preventing further cell cycle progression until replication and repair are complete. In bacteria, cell division is coordinated with chromosome segregation, preventing cell division ring formation over the nucleoid in a process termed nucleoid occlusion. In addition to nucleoid occlusion, bacteria induce the SOS response after replication forks encounter DNA damage or impediments that slow or block their progression. During SOS induction, Escherichia coli expresses a cytoplasmic protein, SulA, that inhibits cell division by directly binding FtsZ. After the SOS response is turned off, SulA is degraded by Lon protease, allowing for cell division to resume. Recently, it has become clear that SulA is restricted to bacteria closely related to E. coli and that most bacteria enforce the DNA damage checkpoint by expressing a small integral membrane protein. Resumption of cell division is then mediated by membrane-bound proteases that cleave the cell division inhibitor. Further, many bacterial cells have mechanisms to inhibit cell division that are regulated independently from the canonical LexA-mediated SOS response. In this review, we discuss several pathways used by bacteria to prevent cell division from occurring when genome instability is detected or before the chromosome has been fully replicated and segregated.

Deregulated expression of the RanBP1 gene alters cell cycle progression in murine fibroblasts

1997 ◽  
Vol 110 (19) ◽  
pp. 2345-2357 ◽  
Author(s):  
A. Battistoni ◽  
G. Guarguaglini ◽  
F. Degrassi ◽  
C. Pittoggi ◽  
A. Palena ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Protein Import ◽  
Proliferating Cells ◽  
Cycle Progression ◽  
Ran Gtpase ◽  
Genes Encoding ◽  
Active Transcription ◽  
Gtpase Cycle

RanBP1 is a molecular partner of the Ran GTPase, which is implicated in the control of several processes, including DNA replication, mitotic entry and exit, cell cycle progression, nuclear structure, protein import and RNA export. While most genes encoding Ran-interacting partners are constitutively active, transcription of the RanBP1 mRNA is repressed in non proliferating cells, is activated at the G1/S transition in cycling cells and peaks during S phase. We report here that forced expression of the RanBP1 gene disrupts the orderly execution of the cell division cycle at several stages, causing inhibition of DNA replication, defective mitotic exit and failure of chromatin decondensation during the telophase-to-interphase transition in cells that achieve nuclear duplication and chromosome segregation. These results suggest that deregulated RanBP1 activity interferes with the Ran GTPase cycle and prevents the functioning of the Ran signalling system during the cell cycle.

scholarly journals Microarray gene expression profiling in colorectal (HCT116) and hepatocellular (HepG2) carcinoma cell lines treated withMelicope ptelefolialeaf extract reveals transcriptome profiles exhibiting anticancer activity

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5203 ◽  
Author(s):  
Mohammad Faujul Kabir ◽  
Johari Mohd Ali ◽  
Onn Haji Hashim
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Dna Replication ◽  
Cell Lines ◽  
Microarray Data ◽  
Expression Profiling ◽  
Cell Cycle Progression ◽  
Anticancer Activities ◽  
Microarray Gene Expression ◽  
Cycle Progression

BackgroundWe have previously reported anticancer activities ofMelicope ptelefolia(MP) leaf extracts on four different cancer cell lines. However, the underlying mechanisms of actions have yet to be deciphered. In the present study, the anticancer activity of MP hexane extract (MP-HX) on colorectal (HCT116) and hepatocellular carcinoma (HepG2) cell lines was characterized through microarray gene expression profiling.MethodsHCT116 and HepG2 cells were treated with MP-HX for 24 hr. Total RNA was extracted from the cells and used for transcriptome profiling using Applied Biosystem GeneChip™ Human Gene 2.0 ST Array. Gene expression data was analysed using an Applied Biosystems Expression Console and Transcriptome Analysis Console software. Pathway enrichment analyses was performed using Ingenuity Pathway Analysis (IPA) software. The microarray data was validated by profiling the expression of 17 genes through quantitative reverse transcription PCR (RT-qPCR).ResultsMP-HX induced differential expression of 1,290 and 1,325 genes in HCT116 and HepG2 cells, respectively (microarray data fold change, MA_FC ≥ ±2.0). The direction of gene expression change for the 17 genes assayed through RT-qPCR agree with the microarray data. In both cell lines, MP-HX modulated the expression of many genes in directions that support antiproliferative activity. IPA software analyses revealed MP-HX modulated canonical pathways, networks and biological processes that are associated with cell cycle, DNA replication, cellular growth and cell proliferation. In both cell lines, upregulation of genes which promote apoptosis, cell cycle arrest and growth inhibition were observed, while genes that are typically overexpressed in diverse human cancers or those that promoted cell cycle progression, DNA replication and cellular proliferation were downregulated. Some of the genes upregulated by MP-HX include pro-apoptotic genes (DDIT3, BBC3, JUN), cell cycle arresting (CDKN1A, CDKN2B), growth arrest/repair (TP53, GADD45A) and metastasis suppression (NDRG1). MP-HX downregulated the expression of genes that could promote anti-apoptotic effect, cell cycle progression, tumor development and progression, which include BIRC5, CCNA2, CCNB1, CCNB2, CCNE2, CDK1/2/6, GINS2, HELLS, MCM2/10 PLK1, RRM2 and SKP2. It is interesting to note that all six top-ranked genes proposed to be cancer-associated (PLK1, MCM2, MCM3, MCM7, MCM10 and SKP2) were downregulated by MP-HX in both cell lines.DiscussionThe present study showed that the anticancer activities of MP-HX are exerted through its actions on genes regulating apoptosis, cell proliferation, DNA replication and cell cycle progression. These findings further project the potential use of MP as a nutraceutical agent for cancer therapeutics.

scholarly journals Adeno-Associated Virus Major Rep78 Protein Disrupts Binding of TATA-Binding Protein to the p97 Promoter of Human Papillomavirus Type 16

2000 ◽  
Vol 74 (5) ◽  
pp. 2459-2465 ◽  
Author(s):  
Pei-Fen Su ◽  
Shu-Yuan Chiang ◽  
Cheng-Wen Wu ◽  
Felicia Y.-H. Wu
Keyword(s):  
Human Papillomavirus ◽  
Binding Protein ◽  
Core Promoter ◽  
Tata Binding Protein ◽  
Tata Box ◽  
Dependent Manner ◽  
Hpv 16 ◽  
Adeno Associated Virus ◽  
Human Papillomavirus Type 16 ◽  
E6 And E7

ABSTRACT Adeno-associated virus type 2 (AAV) is known to inhibit the promoter activities of several oncogenes and viral genes, including the human papillomavirus type 16 (HPV-16) E6 and E7 transforming genes. However, the target elements of AAV on the long control region (LCR) upstream of E6 and E7 oncogenes are elusive. A chloramphenicol acetyltransferase assay was performed to study the effect of AAV on the transcription activity of the HPV-16 LCR in SiHa (HPV-positive) and C-33A (HPV-negative) cells. The results reveal that (i) AAV inhibited HPV-16 LCR activity in a dose-dependent manner, (ii) AAV-mediated inhibition did not require the HPV gene products, and (iii) the AAV replication gene product Rep78 was involved in the inhibition. Deletion mutation analyses of the HPV-16 LCR showed that regulatory elements outside the core promoter region of the LCR may not be direct targets of AAV-mediated inhibition. Further study with the electrophoretic mobility shift assay demonstrated that Rep78 interfered with the binding of TATA-binding protein (TBP) to the TATA box of the p97 core promoter more significantly than it disrupted the preformed TBP-TATA complex. These data thus suggest that Rep78 may inhibit transcription initiation of the HPV-16 LCR by disrupting the interaction between TBP and the TATA box of the p97 core promoter.

scholarly journals Evidence for a dual role for TC4 protein in regulating nuclear structure and cell cycle progression.

1994 ◽  
Vol 125 (4) ◽  
pp. 705-719 ◽  
Author(s):  
S Kornbluth ◽  
M Dasso ◽  
J Newport
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Nuclear Structure ◽  
Cell Cycle Progression ◽  
Cycle Progression ◽  
Nuclear Assembly ◽  
Egg Extracts ◽  
A Cell ◽  
Xenopus Egg Extracts

TC4, a ras-like G protein, has been implicated in the feedback pathway linking the onset of mitosis to the completion of DNA replication. In this report we find distinct roles for TC4 in both nuclear assembly and cell cycle progression. Mutant and wild-type forms of TC4 were added to Xenopus egg extracts capable of assembling nuclei around chromatin templates in vitro. We found that a mutant TC4 protein defective in GTP binding (GDP-bound form) suppressed nuclear growth and prevented DNA replication. Nuclear transport under these conditions approximated normal levels. In a separate set of experiments using a cell-free extract of Xenopus eggs that cycles between S and M phases, the GDP-bound form of TC4 had dramatic effects, blocking entry into mitosis even in the complete absence of nuclei. The effect of this mutant TC4 protein on cell cycle progression is mediated by phosphorylation of p34cdc2 on tyrosine and threonine residues, negatively regulating cdc2 kinase activity. Therefore, we provide direct biochemical evidence for a role of TC4 in both maintaining nuclear structure and in the signaling pathways that regulate entry into mitosis.

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.

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