scholarly journals Differential Requirement of Human Cytomegalovirus UL112-113 Protein Isoforms for Viral Replication

2017 ◽  
Vol 91 (17) ◽  
Author(s):  
Tim Schommartz ◽  
Jiajia Tang ◽  
Rebekka Brost ◽  
Wolfram Brune
Keyword(s):  
Endothelial Cells ◽  
Dna Replication ◽  
Viral Replication ◽  
Dna Polymerase ◽  
Human Cytomegalovirus ◽  
Cell Nucleus ◽  
Human Fibroblasts ◽  
Gene Products ◽  
Viral Dna ◽  
Viral Dna Replication

ABSTRACT The UL112-113 gene is one of the few alternatively spliced genes of human cytomegalovirus (HCMV). It codes for four phosphoproteins, p34, p43, p50, and p84, all of which are expressed with early kinetics and accumulate at sites of viral DNA replication within the host cell nucleus. Although these proteins are known to play important, possibly essential, roles in the viral replication cycle, little is known about the contribution of individual UL112-113 protein products. Here we used splice site mutagenesis, intron deletion and substitution, and nonsense mutagenesis to prevent the individual expression of each UL112-113 protein isoform and to investigate the importance of each isoform for viral replication. We show that HCMV mutants lacking p34 or p50 expression replicated to high titers in human fibroblasts and endothelial cells, indicating that these proteins are nonessential for viral replication, while mutant viruses carrying a stop mutation within the p84 coding sequence were severely growth impaired. Viral replication could not be detected upon the inactivation of p43 expression, indicating that this UL112-113 protein is essential for viral replication. We also analyzed the ability of UL112-113 proteins to recruit other viral proteins to intranuclear prereplication compartments. While UL112-113 expression was sufficient to recruit the UL44-encoded viral DNA polymerase processivity factor, it was not sufficient for the recruitment of the viral UL84 and UL117 proteins. Remarkably, both the p43 and p84 isoforms were required for the efficient recruitment of pUL44, which is consistent with their critical role in the viral life cycle. IMPORTANCE Human cytomegalovirus requires gene products from 11 genetic loci for the lytic replication of its genome. One of these loci, UL112-113, encodes four proteins with common N termini by alternative splicing. In this study, we inactivated the expression of each of the four UL112-113 proteins individually and determined their requirement for HCMV replication. We found that two of the UL112-113 gene products were dispensable for viral replication in human fibroblasts and endothelial cells. In contrast, viral replication was severely reduced or absent when one of the other two gene products was inactivated, indicating that they are of crucial importance for the viral replication cycle. We further showed that the latter two gene products are involved in the recruitment of pUL44, an essential cofactor of the viral DNA polymerase, to specific sites within the cell nucleus that are thought to serve as starting points for viral DNA replication.

scholarly journals The Human Cytomegalovirus IE2 and UL112-113 Proteins Accumulate in Viral DNA Replication Compartments That Initiate from the Periphery of Promyelocytic Leukemia Protein-Associated Nuclear Bodies (PODs or ND10)

1999 ◽  
Vol 73 (12) ◽  
pp. 10458-10471 ◽  
Author(s):  
Jin-Hyun Ahn ◽  
Won-Jong Jang ◽  
Gary S. Hayward
Keyword(s):  
Dna Replication ◽  
Viral Replication ◽  
Human Cytomegalovirus ◽  
Promyelocytic Leukemia ◽  
Nuclear Bodies ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Promyelocytic Leukemia Protein ◽  
The Core ◽  
Replication Compartment

ABSTRACT During human cytomegalovirus (HCMV) infection, the periphery of promyelocytic leukemia protein (PML)-associated nuclear bodies (also known as PML oncogenic domains [PODs] or ND10) are sites for both input viral genome deposition and immediate-early (IE) gene transcription. At very early times after infection, the IE1 protein localizes to and subsequently disrupts PODs, whereas the IE2 protein localizes within or adjacent to PODs. This process appears to be required for efficient viral gene expression and DNA replication. We have investigated the initiation of viral DNA replication compartment formation by studying the localization of viral IE proteins, DNA replication proteins, and the PML protein during productive infection. Localization of IE2 adjacent to PODs between 2 and 6 h after infection was confirmed by confocal microscopy of human fibroblasts (HF cells) infected with both wild-type HCMV(Towne) and with an IE1-deletion mutant HCMV(CR208) that fails to disrupt PODs. In HCMV(Towne)-infected HF cells at 24 to 48 h, IE2 also accumulated in newly formed viral DNA replication compartments containing the polymerase processivity factor (UL44), the single-stranded DNA binding protein (SSB; UL57), the UL112-113 accessory protein, and newly incorporated bromodeoxyuridine (BrdU). Double labeling of the HCMV(CR208)-infected HF cells demonstrated that formation of viral DNA replication compartments initiates within granular structures that bud from the periphery of some of the PODs and subsequently coalesce into larger structures that are flanked by PODs. In transient DNA transfection assays, both the N terminus (codons 136 to 290) and the C terminus (codons 379 to 579) of IE2 exon 5, but not the central region between them, were found to be necessary for both the punctate distribution of IE2 and its association with PODs. Like IE2, the UL112-113 accessory replication protein was also distributed in a POD-associated pattern in both DNA-transfected and virus-infected cells beginning at 6 h. Furthermore, when all six replication core machinery proteins (polymerase complex, SSB, and helicase-primase complex) were expressed together in the presence of UL112-113, they also accumulated at POD-associated sites, suggesting that the UL112-113 protein (but not IE2) may play a role in recruitment of viral replication fork proteins into the periphery of PODs. These results show that (i) subsequent to accumulating at the periphery of PODs, IE2 is incorporated together with the core proteins into viral DNA replication compartments that initiate from the periphery of PODs and then grow to fill the space between groups of PODs, and (ii) the UL112-113 protein appears to have a key role in assembling and recruiting the core replication machinery proteins in the initial stages of viral replication compartment formation.

scholarly journals A Noncanonical Function of Polycomb Repressive Complexes Promotes Human Cytomegalovirus Lytic DNA Replication and Serves as a Novel Cellular Target for Antiviral Intervention

2019 ◽  
Vol 93 (9) ◽  
Author(s):  
Adriana Svrlanska ◽  
Anna Reichel ◽  
Eva-Maria Schilling ◽  
Myriam Scherer ◽  
Thomas Stamminger ◽  
...  
Keyword(s):  
Dna Replication ◽  
Viral Replication ◽  
Human Cytomegalovirus ◽  
Cellular Proliferation ◽  
Antiviral Treatment ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Cellular Target ◽  
Core Components ◽  
Polycomb Repressive Complexes

ABSTRACTChromatin-based modifications of herpesviral genomes play a crucial role in dictating the outcome of infection. Consistent with this, host cell multiprotein complexes, such as polycomb repressive complexes (PRCs), were proposed to act as epigenetic regulators of herpesviral latency. In particular, PRC2 has recently been shown to contribute to the silencing of human cytomegalovirus (HCMV) genomes. Here, we identify a novel proviral role of PRC1 and PRC2, the two main polycomb repressive complexes, during productive HCMV infection. Western blot analyses revealed strong HCMV-mediated upregulation of RING finger protein 1B (RING1B) and B lymphoma Moloney murine leukemia virus insertion region 1 homolog (BMI1) as well as of enhancer of zeste homolog 2 (EZH2), suppressor of zeste 12 (SUZ12), and embryonic ectoderm development (EED), which constitute the core components of PRC1 and PRC2, respectively. Furthermore, we observed a relocalization of PRC components to viral replication compartments, whereas histone modifications conferred by the respective PRCs were specifically excluded from these sites. Depletion of individual PRC1/PRC2 proteins by RNA interference resulted in a significant reduction of newly synthesized viral genomes and, in consequence, a decreased release of viral particles. Furthermore, accelerated native isolation of protein on nascent DNA (aniPOND) revealed a physical association of EZH2 and BMI1 with nascent HCMV DNA, suggesting a direct contribution of PRC proteins to viral DNA replication. Strikingly, substances solely inhibiting the enzymatic activity of PRC1/2 did not exert antiviral effects, while drugs affecting the abundance of PRC core components strongly compromised HCMV genome synthesis and particle release. Taken together, our data reveal an enzymatically independent, noncanonical function of both PRC1 and PRC2 during HCMV DNA replication, which may serve as a novel cellular target for antiviral therapy.IMPORTANCEPolycomb group (PcG) proteins are primarily known as transcriptional repressors that modify chromatin and contribute to the establishment and maintenance of cell fates. Furthermore, emerging evidence indicates that overexpression of PcG proteins in various types of cancers contributes to the dysregulation of cellular proliferation. Consequently, several inhibitors targeting PcG proteins are presently undergoing preclinical and clinical evaluation. Here, we show that infection with human cytomegalovirus also induces a strong upregulation of several PcG proteins. Our data suggest that viral DNA replication depends on a noncanonical function of polycomb repressor complexes which is independent of the so-far-described enzymatic activities of individual PcG factors. Importantly, we observe that a subclass of inhibitory drugs that affect the abundance of PcG proteins strongly interferes with viral replication. This principle may serve as a novel promising target for antiviral treatment.

scholarly journals Analysis of the Association of the Human Cytomegalovirus DNA Polymerase Subunit UL44 with the Viral DNA Replication Factor UL84

2009 ◽  
Vol 83 (15) ◽  
pp. 7581-7589 ◽  
Author(s):  
Blair L. Strang ◽  
Elisa Sinigalia ◽  
Laurie A. Silva ◽  
Donald M. Coen ◽  
Arianna Loregian
Keyword(s):  
Dna Replication ◽  
Infected Cell ◽  
Dna Polymerase ◽  
Human Cytomegalovirus ◽  
Nuclear Antigen ◽  
Replication Proteins ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Processivity Factor ◽  
Replication Factors

ABSTRACT The central enzyme responsible for human cytomegalovirus (HCMV) DNA synthesis is a virally encoded DNA polymerase that includes a catalytic subunit, UL54, and a homodimeric accessory subunit, UL44, the presumptive HCMV DNA polymerase processivity factor. The structure of UL44 is similar to that of the eukaryotic processivity factor proliferating cell nuclear antigen (PCNA), which interacts with numerous other proteins required for faithful DNA replication. We sought to determine whether, like PCNA, UL44 is capable of interacting with multiple DNA replication proteins and, if so, whether these proteins bind UL44 at the site corresponding to where multiple proteins bind to PCNA. Initially, several proteins, including the viral DNA replication factors UL84 and UL57, were identified by mass spectrometry in immunoprecipitates of UL44 from infected cell lysate. The association of UL44/UL84, but not UL44/UL57, was confirmed by reciprocal coimmunoprecipitation of these proteins from infected cell lysates and was resistant to nuclease treatment. Yeast two-hybrid analyses demonstrated that the substitution of residues in UL44 that prevent UL44 homodimerization or abrogate the binding of UL54 to UL44 do not abrogate the UL44/UL84 interaction. Reciprocal glutathione-S-transferase (GST) pulldown experiments using bacterially expressed UL44 and UL84 confirmed these results and, further, demonstrated that a UL54-derived peptide that competes with UL54 for UL44 binding does not prevent the association of UL84 with UL44. Taken together, our results strongly suggest that UL44 and UL84 interact directly using a region of UL44 different from the UL54 binding site. Thus, UL44 can bind interacting replication proteins using a mechanism different from that of PCNA.

scholarly journals Defective Growth Correlates with Reduced Accumulation of a Viral DNA Replication Protein after Low-Multiplicity Infection by a Human Cytomegalovirus ie1 Mutant

1998 ◽  
Vol 72 (1) ◽  
pp. 366-379 ◽  
Author(s):  
Richard F. Greaves ◽  
Edward S. Mocarski
Keyword(s):  
Dna Replication ◽  
Human Cytomegalovirus ◽  
Human Fibroblasts ◽  
Lytic Replication ◽  
Early Gene ◽  
Similar Proportion ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Primary Fibroblasts ◽  
Infected Cells

ABSTRACT To investigate the importance of the IE1 p72 regulatory protein during human cytomegalovirus replication, a recombinant virus unable to synthesize IE1 p72 was constructed. The Towne strain mutant CR208 lacked exon 4 of the major immediate-early gene and was isolated and complemented in an IE1-expressing immortalized human fibroblast line (ihfie1.3). Replication of CR208 in primary human fibroblasts was completed after an input multiplicity of 10 PFU/cell but was severely impaired at 0.1 PFU/cell. CR208 formed plaques with lower efficiency on primary fibroblasts than on ihfie1.3 cells, and the relationship between the CR208 inoculum size and the resulting number of undersized plaques was nonlinear, indicating that multiple particles of CR208 were required to initiate lytic replication in a single primary fibroblast. After infection of primary fibroblasts with CR208 at 5 PFU/cell, a normal pattern of viral antigens was detected, although IE1 p72 was absent. During lower-multiplicity infections, IE2 protein was consistently detected at similar levels in a similar proportion of CR208-infected cells relative to the case for a Towne infection, but many fewer CR208-infected cells contained the ppUL44 polymerase accessory protein when evaluated at 24 or 48 h after infection. Furthermore, fibroblasts infected with CR208 at a low multiplicity failed to form viral DNA replication compartments, despite having expressed IE2 p86. These low-multiplicity growth and expression defects were corrected in two rescued derivatives of CR208 able to synthesize IE1 p72. One rescued virus (CR249) carried a deletion removing the large intron between exons 1 and 2 of the ie1-ie2 locus, revealing that this intron was dispensable for growth in cell culture.

scholarly journals Inhibition of Human Cytomegalovirus DNA Replication with a Phosphorothioate Cholesteryl-Modified Oligonucleotide is Mediated by Rapid Cellular Association and Virus-Facilitated Nuclear Localization

1997 ◽  
Vol 8 (3) ◽  
pp. 255-264 ◽  
Author(s):  
Z Zhang ◽  
JA Smith ◽  
AP Smyth ◽  
J-Y Tang ◽  
W Eisenberg ◽  
...  
Keyword(s):  
Dna Replication ◽  
Human Cytomegalovirus ◽  
Nuclear Localization ◽  
Antimicrobial Agents ◽  
Human Fibroblasts ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Nuclease Resistance ◽  
Infected Cells ◽  
Modified Oligonucleotide

We have previously shown that an antisense phosphorothioate (PS) oligodeoxynucleotide has potent anti-human cytomegalovirus (HCMV) activity (GS Pari, AK Field & JA Smith, Antimicrobial Agents and Chemotherapy 1995, 39: 1157–1161). We have now used a modified PS oligonucleotide having three 2′-O-methyl nucleotides at the 3′ end and four 2′-O-methyl nucleotides at the 5′ end, containing a cholesteryl moiety linked to the 3′ end by a novel thiono-triester linkage. This compound, UL36ANTI-M, is superior to the PS (UL36ANTI) version with respect to antiviral potency, melting temperature and nuclease resistance. Also, we show that cellular association for this oligonucleotide is rapid, occurring within 15 min after treatment and is about 12-fold higher when compared to UL36ANTI. This increased rate of cellular association also correlates with antiviral properties in that a 15 min incubation with UL36ANTI-M was sufficient to achieve 75% inhibition of viral DNA replication and complete inhibition was achieved after only a 1 h pretreatment. In addition confocal microscopic examination showed a change in subcellular distribution from perinuclear to nuclear for oligonucleotides in HCMV-infected human fibroblasts. However, the total amount of cell-associated oligonucleotide was unchanged in infected cells.

scholarly journals Histone H3 Lysine 4 Methylation Marks Postreplicative Human Cytomegalovirus Chromatin

2012 ◽  
Vol 86 (18) ◽  
pp. 9817-9827 ◽  
Author(s):  
Alexandra Nitzsche ◽  
Charlotte Steinhäußer ◽  
Katrin Mücke ◽  
Christina Paulus ◽  
Michael Nevels
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Histone Modification ◽  
Dna Polymerase ◽  
Human Cytomegalovirus ◽  
Viral Genome ◽  
Histone H3 ◽  
Viral Dna ◽  
The Impact ◽  
Preferential Incorporation

In the nuclei of permissive cells, human cytomegalovirus genomes form nucleosomal structures initially resembling heterochromatin but gradually switching to a euchromatin-like state. This switch is characterized by a decrease in histone H3 K9 methylation and a marked increase in H3 tail acetylation and H3 K4 methylation across the viral genome. We used ganciclovir and a mutant virus encoding a reversibly destabilized DNA polymerase to examine the impact of DNA replication on histone modification dynamics at the viral chromatin. The changes in H3 tail acetylation and H3 K9 methylation proceeded in a DNA replication-independent fashion. In contrast, the increase in H3 K4 methylation proved to depend widely on viral DNA synthesis. Consistently, labeling of nascent DNA using “click chemistry” revealed preferential incorporation of methylated H3 K4 into viral (but not cellular) chromatin during or following DNA replication. This study demonstrates largely selective epigenetic tagging of postreplicative human cytomegalovirus chromatin.

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