scholarly journals Control functions of adenovirus transformation region E1A gene products in rat and human cells.

1985 ◽  
Vol 5 (8) ◽  
pp. 1933-1939 ◽  
Author(s):  
A J Bellett ◽  
P Li ◽  
E T David ◽  
E J Mackey ◽  
A W Braithwaite ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Cell Cycle Control ◽  
Viral Gene Expression ◽  
Human Cells ◽  
Early Gene ◽  
Wild Type Virus ◽  
Viral Gene ◽  
Altered Cell

Altered control of the rat cell cycle induced by adenovirus requires expression of transformation region E1A, but not of E1B, E2A, E2B, or late genes. We show here that neither E3 nor E4 is required, so the effect results directly from an E1A product. Mutants with defects in the 289-amino-acid (aa) E1A product had little or no effect on the rat cell cycle even at 1,000 IU per cell. A mutant (pm975) lacking the 243-aa E1A product altered cell cycle progression, but less efficiently than did wild-type virus. The 289-aa E1A protein is therefore essential for cell cycle effects; the 243-aa protein is also necessary for the full effect but cannot act alone. Mutants with altered 289-aa E1A proteins showed different extents of leak expression of viral early region E2A as the multiplicity was increased; each leaked more in human than in rat cells. dl312, with no E1A products, failed to produce E2A mRNA or protein at 1,000 IU per cell in rat cells but did so in some experiments in human cells. There appears to be a very strict dependence of viral early gene expression on E1A in rat cells, whereas dependence on E1A is more relaxed in HeLa cells, perhaps due to a cellular E1A-like function. Altered cell cycle control is more dependent on E1A function than is early viral gene expression.

Control functions of adenovirus transformation region E1A gene products in rat and human cells

1985 ◽  
Vol 5 (8) ◽  
pp. 1933-1939
Author(s):  
A J Bellett ◽  
P Li ◽  
E T David ◽  
E J Mackey ◽  
A W Braithwaite ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Cell Cycle Control ◽  
Viral Gene Expression ◽  
Human Cells ◽  
Early Gene ◽  
Wild Type Virus ◽  
Viral Gene ◽  
Altered Cell

Altered control of the rat cell cycle induced by adenovirus requires expression of transformation region E1A, but not of E1B, E2A, E2B, or late genes. We show here that neither E3 nor E4 is required, so the effect results directly from an E1A product. Mutants with defects in the 289-amino-acid (aa) E1A product had little or no effect on the rat cell cycle even at 1,000 IU per cell. A mutant (pm975) lacking the 243-aa E1A product altered cell cycle progression, but less efficiently than did wild-type virus. The 289-aa E1A protein is therefore essential for cell cycle effects; the 243-aa protein is also necessary for the full effect but cannot act alone. Mutants with altered 289-aa E1A proteins showed different extents of leak expression of viral early region E2A as the multiplicity was increased; each leaked more in human than in rat cells. dl312, with no E1A products, failed to produce E2A mRNA or protein at 1,000 IU per cell in rat cells but did so in some experiments in human cells. There appears to be a very strict dependence of viral early gene expression on E1A in rat cells, whereas dependence on E1A is more relaxed in HeLa cells, perhaps due to a cellular E1A-like function. Altered cell cycle control is more dependent on E1A function than is early viral gene expression.

scholarly journals Cell-to-cell and genome-to-genome variability of adenovirus transcription tuned by the cell cycle

2020 ◽  
Vol 134 (5) ◽  
pp. jcs252544
Author(s):  
Maarit Suomalainen ◽  
Vibhu Prasad ◽  
Abhilash Kannan ◽  
Urs F. Greber
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Single Molecule ◽  
Click Reaction ◽  
Viral Gene Expression ◽  
Early Gene ◽  
Viral Gene ◽  
Viral Genomes ◽  
E1a Gene ◽  
G1 Cells

ABSTRACTIn clonal cultures, not all cells are equally susceptible to virus infection, and the mechanisms underlying this are poorly understood. Here, we developed image-based single-cell measurements to scrutinize the heterogeneity of adenovirus (AdV) infection. AdV delivers, transcribes and replicates a linear double-stranded DNA genome in the nucleus. We measured the abundance of viral transcripts using single-molecule RNA fluorescence in situ hybridization (FISH) and the incoming 5-ethynyl-2′-deoxycytidine (EdC)-tagged viral genomes using a copper(I)-catalyzed azide–alkyne cycloaddition (click) reaction. Surprisingly, expression of the immediate early gene E1A only moderately correlated with the number of viral genomes in the cell nucleus. Intranuclear genome-to-genome heterogeneity was found at the level of viral transcription and, in accordance, individual genomes exhibited heterogeneous replication activity. By analyzing the cell cycle state, we found that G1 cells exhibited the highest E1A gene expression and displayed increased correlation between E1A gene expression and viral genome copy numbers. The combined image-based single-molecule procedures described here are ideally suited to explore the cell-to-cell variability in viral gene expression in a range of different settings, including the innate immune response.

scholarly journals Cell Cycle-Independent Expression of Immediate-Early Gene 3 Results in G1 and G2 Arrest in Murine Cytomegalovirus-Infected Cells

2008 ◽  
Vol 82 (20) ◽  
pp. 10188-10198 ◽  
Author(s):  
Lüder Wiebusch ◽  
Anke Neuwirth ◽  
Linus Grabenhenrich ◽  
Sebastian Voigt ◽  
Christian Hagemeier
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Viral Gene Expression ◽  
Immediate Early Gene ◽  
Early Gene ◽  
Immediate Early ◽  
Viral Gene ◽  
Cycle Arrest ◽  
Infected Cells

ABSTRACT The infectious cycle of human cytomegalovirus (HCMV) is intricately linked to the host's cell cycle. Viral gene expression can be initiated only in G0/G1 phase. Once expressed, the immediate-early gene product IE2 prevents cellular DNA synthesis, arresting infected cells with a G1 DNA content. This function is required for efficient viral replication in vitro. A prerequisite for addressing its in vivo relevance is the characterization of cell cycle-regulatory activities of CMV species for which animal models have been established. Here, we show that murine CMV (MCMV), like HCMV, has a strong antiproliferative capacity and arrests cells in G1. Unexpectedly, and in contrast to HCMV, MCMV can also block cells that have passed through S phase by arresting them in G2. Moreover, MCMV can also replicate in G2 cells. This is made possible by the cell cycle-independent expression of MCMV immediate-early genes. Transfection experiments show that of several MCMV candidate genes, only immediate-early gene 3 (ie3), the homologue of HCMV IE2, exhibits cell cycle arrest activity. Accordingly, an MCMV ie3 deletion mutant has lost the ability to arrest cells in either G1 or G2. Thus, despite interspecies variations in the cell cycle dependence of viral gene expression, the central theme of HCMV IE2-induced cell cycle arrest is conserved in the murine counterpart, raising the possibility of studying its physiological relevance at the level of the whole organism.

scholarly journals Human Cytomegalovirus 86-Kilodalton IE2 Protein Blocks Cell Cycle Progression in G1

1999 ◽  
Vol 73 (11) ◽  
pp. 9274-9283 ◽  
Author(s):  
Lüder Wiebusch ◽  
Christian Hagemeier
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Human Cytomegalovirus ◽  
Transcriptional Activation ◽  
Cell Cycle Progression ◽  
Biological Activities ◽  
Viral Gene Expression ◽  
Viral Gene ◽  
Proliferating Cells ◽  
Activation Domains

ABSTRACT The 86-kDa IE2 protein of human cytomegalovirus (HCMV) is an important regulator of viral and host cell gene expression. Still, besides its function as a transcription factor, little is known about the biological activities of IE2. Here, we show that IE2 can induce a G1 arrest in several different cell lines, including HCMV-permissive U-373 cells. The known transcriptional activation domains of IE2 are dispensable for G1 arrest, favoring a posttranscriptional mechanism mediating this cell cycle effect. We show that like human primary fibroblasts U-373 cells arrest in G1 upon infection with HCMV. This G1 arrest occurs within 24 h after infection and in proliferating cells depends on viral gene expression. Our data therefore suggest that IE2 is at least partially responsible for blocking the transition from G1 to S phase, which is induced when cells are infected with HCMV.

scholarly journals Actin-based motility drives baculovirus transit to the nucleus and cell surface

2010 ◽  
Vol 190 (2) ◽  
pp. 187-195 ◽  
Author(s):  
Taro Ohkawa ◽  
Loy E. Volkman ◽  
Matthew D. Welch
Keyword(s):  
Gene Expression ◽  
Actin Polymerization ◽  
Nuclear Periphery ◽  
Viral Gene Expression ◽  
Early Gene ◽  
Evolutionary Strategy ◽  
Viral Gene ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nuclear Entry

Most viruses move intracellularly to and from their sites of replication using microtubule-based mechanisms. In this study, we show that nucleocapsids of the baculovirus Autographa californica multiple nucleopolyhedrovirus undergo intracellular motility driven by actin polymerization. Motility requires the viral P78/83 capsid protein and the host Arp2/3 complex. Surprisingly, the virus directs two sequential and coordinated phases of actin-based motility. Immediately after cell entry, motility enables exploration of the cytoplasm and collision with the nuclear periphery, speeding nuclear entry and the initiation of viral gene expression. Nuclear entry itself requires transit through nuclear pore complexes. Later, after the onset of early gene expression, motility is required for accumulation of a subpopulation of nucleocapsids in the tips of actin-rich surface spikes. Temporal coordination of actin-based nuclear and surface translocation likely enables rapid transmission to neighboring cells during infection in insects and represents a distinctive evolutionary strategy for overcoming host defenses.

scholarly journals Highly Divergent Lentiviral Tat Proteins Activate Viral Gene Expression by a Common Mechanism

1999 ◽  
Vol 19 (7) ◽  
pp. 4592-4599 ◽  
Author(s):  
Paul D. Bieniasz ◽  
Therese A. Grdina ◽  
Hal P. Bogerd ◽  
Bryan R. Cullen
Keyword(s):  
Gene Expression ◽  
Protein Complex ◽  
Equine Infectious Anemia Virus ◽  
Viral Gene Expression ◽  
Human Cells ◽  
Common Mechanism ◽  
Viral Gene ◽  
Target Element ◽  
Anemia Virus ◽  
Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) Tat protein (hTat) activates transcription initiated at the viral long terminal repeat (LTR) promoter by a unique mechanism requiring recruitment of the human cyclin T1 (hCycT1) cofactor to the viral TAR RNA target element. While activation of equine infectious anemia virus (EIAV) gene expression by the EIAV Tat (eTat) protein appears similar in that the target element is a promoter proximal RNA, eTat shows little sequence homology to hTat, does not activate the HIV-1 LTR, and is not active in human cells that effectively support hTat function. To address whether eTat and hTat utilize similar or distinct mechanisms of action, we have cloned the equine homolog of hCycT1 (eCycT1) and examined whether it is required to mediate eTat function. Here, we report that expression of eCycT1 in human cells fully rescues eTat function and that eCycT1 and eTat form a protein complex that specifically binds to the EIAV, but not the HIV-1, TAR element. While hCycT1 is also shown to interact with eTat, the lack of eTat function in human cells is explained by the failure of the resultant protein complex to bind to EIAV TAR. Critical sequences in eCycT1 required to support eTat function are located very close to the amino terminus, i.e., distal to the HIV-1 Tat-TAR interaction motif previously identified in the hCycT1 protein. Together, these data provide a molecular explanation for the species tropism displayed by eTat and demonstrate that highly divergent lentiviral Tat proteins activate transcription from their cognate LTR promoters by essentially identical mechanisms.

Cell-cycle-dependent localization of human cytomegalovirus UL83 phosphoprotein in the nucleolus and modulation of viral gene expression in human embryo fibroblasts in vitro

2011 ◽  
Vol 112 (1) ◽  
pp. 307-317 ◽  
Author(s):  
Maria-Cristina Arcangeletti ◽  
Isabella Rodighiero ◽  
Prisco Mirandola ◽  
Flora De Conto ◽  
Silvia Covan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Human Cytomegalovirus ◽  
Human Embryo ◽  
Viral Gene Expression ◽  
Viral Gene ◽  
Embryo Fibroblasts ◽  
Cycle Dependent

scholarly journals MicroRNA miR-21 Attenuates Human Cytomegalovirus Replication in Neural Cells by Targeting Cdc25a

2014 ◽  
Vol 89 (2) ◽  
pp. 1070-1082 ◽  
Author(s):  
Ya-Ru Fu ◽  
Xi-Juan Liu ◽  
Xiao-Jun Li ◽  
Zhang-zhou Shen ◽  
Bo Yang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Stem Cells ◽  
Birth Defects ◽  
Human Cytomegalovirus ◽  
Hcmv Infection ◽  
Viral Gene Expression ◽  
Viral Gene ◽  
Gene Products ◽  
Hcmv Replication

ABSTRACTCongenital human cytomegalovirus (HCMV) infection is a leading cause of birth defects, primarily manifesting as neurological disorders. HCMV infection alters expression of cellular microRNAs (miRs) and induces cell cycle arrest, which in turn modifies the cellular environment to favor virus replication. Previous observations found that HCMV infection reduces miR-21 expression in neural progenitor/stem cells (NPCs). Here, we show that infection of NPCs and U-251MG cells represses miR-21 while increasing the levels of Cdc25a, a cell cycle regulator and known target of miR-21. These opposing responses to infection prompted an investigation of the relationship between miR-21, Cdc25a, and viral replication. Overexpression of miR-21 in NPCs and U-251MG cells inhibited viral gene expression, genome replication, and production of infectious progeny, while shRNA-knockdown of miR-21 in U-251MG cells increased viral gene expression. In contrast, overexpression of Cdc25a in U-251MG cells increased viral gene expression and production of infectious progeny and overcame the inhibitory effects of miR-21 overexpression. Three viral gene products—IE1, pp71, and UL26—were shown to inhibit miR-21 expression at the transcriptional level. These results suggest that Cdc25a promotes HCMV replication and elevation of Cdc25a levels after HCMV infection are due in part to HCMV-mediated repression of miR-21. Thus, miR-21 is an intrinsic antiviral factor that is modulated by HCMV infection. This suggests a role for miR-21 downregulation in the neuropathogenesis of HCMV infection of the developing CNS.IMPORTANCEHuman cytomegalovirus (HCMV) is a ubiquitous pathogen and has very high prevalence among population, especially in China, and congenital HCMV infection is a major cause for birth defects. Elucidating virus-host interactions that govern HCMV replication in neuronal cells is critical to understanding the neuropathogenesis of birth defects resulting from congenital infection. In this study, we confirm that HCMV infection downregulates miR-21 but upregulates Cdc25a. Further determined the negative effects of cellular miRNA miR-21 on HCMV replication in neural progenitor/stem cells and U-251MG glioblastoma/astrocytoma cells. More importantly, our results provide the first evidence that miR-21 negatively regulates HCMV replication by targeting Cdc25a, a vital cell cycle regulator. We further found that viral gene products of IE1, pp71, and UL26 play roles in inhibiting miR-21 expression, which in turn causes increases in Cdc25a and benefits HCMV replication. Thus, miR-21 appears to be an intrinsic antiviral factor that represents a potential target for therapeutic intervention.

scholarly journals CCCTC-Binding Factor Recruitment to the Early Region of the Human Papillomavirus 18 Genome Regulates Viral Oncogene Expression

2015 ◽  
Vol 89 (9) ◽  
pp. 4770-4785 ◽  
Author(s):  
Christian Paris ◽  
Ieisha Pentland ◽  
Ian Groves ◽  
David C. Roberts ◽  
Simon J. Powis ◽  
...  
Keyword(s):  
Gene Expression ◽  
High Risk ◽  
Host Cell ◽  
Viral Gene Expression ◽  
Early Gene ◽  
Ctcf Binding ◽  
Ctcf Binding Site ◽  
Viral Gene ◽  
Genome Wide ◽  
High Risk Hpv

ABSTRACTHost cell differentiation-dependent regulation of human papillomavirus (HPV) gene expression is required for productive infection. The host cell CCCTC-binding factor (CTCF) functions in genome-wide chromatin organization and gene regulation. We have identified a conserved CTCF binding site in the E2 open reading frame of high-risk HPV types. Using organotypic raft cultures of primary human keratinocytes containing high-risk HPV18 genomes, we show that CTCF recruitment to this conserved site regulates viral gene expression in differentiating epithelia. Mutation of the CTCF binding site increases the expression of the viral oncoproteins E6 and E7 and promotes host cell proliferation. Loss of CTCF binding results in a reduction of a specific alternatively spliced transcript expressed from the early gene region concomitant with an increase in the abundance of unspliced early transcripts. We conclude that high-risk HPV types have evolved to recruit CTCF to the early gene region to control the balance and complexity of splicing events that regulate viral oncoprotein expression.IMPORTANCEThe establishment and maintenance of HPV infection in undifferentiated basal cells of the squamous epithelia requires the activation of a subset of viral genes, termed early genes. The differentiation of infected cells initiates the expression of the late viral transcripts, allowing completion of the virus life cycle. This tightly controlled balance of differentiation-dependent viral gene expression allows the virus to stimulate cellular proliferation to support viral genome replication with minimal activation of the host immune response, promoting virus productivity. Alternative splicing of viral mRNAs further increases the complexity of viral gene expression. In this study, we show that the essential host cell protein CTCF, which functions in genome-wide chromatin organization and gene regulation, is recruited to the HPV genome and plays an essential role in the regulation of early viral gene expression and transcript processing. These data highlight a novel virus-host interaction important for HPV pathogenicity.

scholarly journals Chromatin Modulation of Herpesvirus Lytic Gene Expression: Managing Nucleosome Density and Heterochromatic Histone Modifications

mBio ◽  
2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Thomas M. Kristie
Keyword(s):  
Gene Expression ◽  
Histone Modifications ◽  
Viral Gene Expression ◽  
Virus Genome ◽  
Early Gene ◽  
Productive Infection ◽  
Viral Gene ◽  
Early Protein ◽  
Protein Icp0 ◽  
Simplex Virus

ABSTRACT Like their cellular hosts, herpesviruses are subject to the regulatory impacts of chromatin assembled on their genomes. Upon infection, these viruses are assembled into domains of chromatin with heterochromatic signatures that suppress viral gene expression or euchromatic characteristics that promote gene expression. The organization and modulation of these chromatin domains appear to be intimately linked to the coordinated expression of the different classes of viral genes and thus ultimately play an important role in the progression of productive infection or the establishment and maintenance of viral latency. A recent report from the Knipe laboratory (J. S. Lee, P. Raja, and D. M. Knipe, mBio 7:e02007-15, 2016) contributes to the understanding of the dynamic modulation of chromatin assembled on the herpes simplex virus genome by monitoring the levels of characteristic heterochromatic histone modifications (histone H3 lysine 9 and 27 methylation) associated with a model viral early gene during the progression of lytic infection. Additionally, this study builds upon previous observations that the viral immediate-early protein ICP0 plays a role in reducing the levels of heterochromatin associated with the early genes.

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