scholarly journals Targeting mitotic chromosomes: a conserved mechanism to ensure viral genome persistence

2009 ◽  
Vol 276 (1662) ◽  
pp. 1535-1544 ◽  
Author(s):  
Katherine M Feeney ◽  
Joanna L Parish
Keyword(s):  
Host Cell ◽  
Genetic Material ◽  
Membrane Integrity ◽  
Mitotic Chromosomes ◽  
Nuclear Retention ◽  
Viral Genomes ◽  
Daughter Cells ◽  
Dna Damage Checkpoints ◽  
Low Copy Number ◽  
Dividing Cells

Viruses that maintain their genomes as extrachromosomal circular DNA molecules and establish infection in actively dividing cells must ensure retention of their genomes within the nuclear envelope in order to prevent genome loss. The loss of nuclear membrane integrity during mitosis dictates that paired host cell chromosomes are captured and organized by the mitotic spindle apparatus before segregation to daughter cells. This prevents inaccurate chromosomal segregation and loss of genetic material. A similar mechanism may also exist for the nuclear retention of extrachromosomal viral genomes or episomes during mitosis, particularly for genomes maintained at a low copy number in latent infections. It has been heavily debated whether such a mechanism exists and to what extent this mechanism is conserved among diverse viruses. Research over the last two decades has provided a wealth of information regarding the mechanisms by which specific tumour viruses evade mitotic and DNA damage checkpoints. Here, we discuss the similarities and differences in how specific viruses tether episomal genomes to host cell chromosomes during mitosis to ensure long-term persistence.

scholarly journals Hitchhiking of Viral Genomes on Cellular Chromosomes

2019 ◽  
Vol 6 (1) ◽  
pp. 275-296 ◽  
Author(s):  
Tami L. Coursey ◽  
Alison A. McBride
Keyword(s):  
Viral Genome ◽  
Viral Infections ◽  
Genome Replication ◽  
Mitotic Chromosomes ◽  
Dna Viruses ◽  
Viral Genomes ◽  
Barr Virus ◽  
Dividing Cells ◽  
Viral Genome Replication ◽  
Epstein Barr

Persistent viral infections require a host cell reservoir that maintains functional copies of the viral genome. To this end, several DNA viruses maintain their genomes as extrachromosomal DNA minichromosomes in actively dividing cells. These viruses typically encode a viral protein that binds specifically to viral DNA genomes and tethers them to host mitotic chromosomes, thus enabling the viral genomes to hitchhike or piggyback into daughter cells. Viruses that use this tethering mechanism include papillomaviruses and the gammaherpesviruses Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus. This review describes the advantages and consequences of persistent extrachromosomal viral genome replication.

scholarly journals Kaposi’s Sarcoma-Associated Herpesvirus LANA-Adjacent Regions with Distinct Functions in Episome Segregation or Maintenance

2019 ◽  
Vol 93 (6) ◽  
Author(s):  
Franceline Juillard ◽  
Erika De León Vázquez ◽  
Min Tan ◽  
Shijun Li ◽  
Kenneth M. Kaye
Keyword(s):  
Dna Replication ◽  
Daughter Cell ◽  
Upstream Sequence ◽  
Cell Nuclei ◽  
Mitotic Chromosomes ◽  
Repeat Elements ◽  
Viral Genomes ◽  
Daughter Cells ◽  
Internal Repeat ◽  
Carboxy Terminal

ABSTRACTKaposi’s sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen (LANA) is a 1,162-amino-acid protein that mediates episome persistence of viral genomes. LANA binds the KSHV terminal-repeat (TR) sequence through its carboxy-terminal domain to mediate DNA replication. LANA simultaneously binds mitotic chromosomes and TR DNA to segregate virus genomes to daughter cell nuclei. Amino-terminal LANA attaches to chromosomes by binding histones H2A/H2B, and carboxy-terminal LANA contributes to mitotic-chromosome binding. Although amino- and carboxy-terminal LANA are essential for episome persistence, they are not sufficient, since deletion of all internal LANA sequence renders LANA highly deficient for episome maintenance. Internal LANA sequence upstream of the internal repeat elements contributes to episome segregation and persistence. Here, we investigate this region with a panel of LANA deletion mutants. Mutants retained the ability to associate with mitotic chromosomes and bind TR DNA. In contrast to prior results, deletion of most of this sequence did not reduce LANA’s ability to mediate DNA replication. Deletions of upstream sequence within the region compromised segregation of TR DNA to daughter cells, as assessed by retention of green fluorescent protein (GFP) expression from a replication-deficient TR plasmid. However, deletion of this upstream sequence did not reduce episome maintenance. In contrast, deletions that included an 80-amino-acid sequence immediately downstream resulted in highly deficient episome persistence. LANA with this downstream sequence deleted maintained the ability to replicate and segregate TR DNA, suggesting a unique role for the residues. Therefore, this work identifies adjacent LANA regions with distinct roles in episome segregation and persistence.IMPORTANCEKSHV LANA mediates episomal persistence of viral genomes. LANA binds the KSHV terminal-repeat (TR) sequence to mediate DNA replication and tethers KSHV DNA to mitotic chromosomes to segregate genomes to daughter cell nuclei. Here, we investigate LANA sequence upstream of the internal repeat elements that contributes to episome segregation and persistence. Mutants with deletions within this sequence maintained the ability to bind mitotic chromosomes or bind and replicate TR DNA. Deletion of upstream sequence within the region reduced segregation of TR DNA to daughter cells, but not episome maintenance. In contrast, mutants with deletions of 80 amino acids immediately downstream were highly deficient for episome persistence yet maintained the ability to replicate and segregate TR DNA, the two principal components of episome persistence, suggesting another role for the residues. In summary, this work identifies adjacent LANA sequence with distinct roles in episome segregation and persistence.

scholarly journals Phosphorylation Regulates Binding of the Human Papillomavirus Type 8 E2 Protein to Host Chromosomes

2012 ◽  
Vol 86 (18) ◽  
pp. 10047-10058 ◽  
Author(s):  
Vandana Sekhar ◽  
Alison A. McBride
Keyword(s):  
Human Papillomavirus ◽  
Posttranslational Modifications ◽  
S Phase ◽  
Chromatin Binding ◽  
Genome Maintenance ◽  
Mitotic Chromosomes ◽  
E2 Protein ◽  
Viral Genomes ◽  
Daughter Cells ◽  
Host Nucleus

The papillomavirus E2 proteins are indispensable for the viral life cycle, and their functions are subject to tight regulation. The E2 proteins undergo posttranslational modifications that regulate their properties and roles in viral transcription, replication, and genome maintenance. During persistent infection, the E2 proteins from many papillomaviruses act as molecular bridges that tether the viral genomes to host chromosomes to retain them within the host nucleus and to partition them to daughter cells. The betapapillomavirus E2 proteins bind to pericentromeric regions of host mitotic chromosomes, including the ribosomal DNA loci. We recently reported that two residues (arginine 250 and serine 253) within the chromosome binding region of the human papillomavirus type 8 (HPV8) E2 protein are required for this binding. In this study, we show that serine 253 is phosphorylated, most likely by protein kinase A, and this modulates the interaction of the E2 protein with cellular chromatin. Furthermore, we show that this phosphorylation occurs in S phase, increases the half-life of the E2 protein, and promotes chromatin binding from S phase through mitosis.

scholarly journals E1 Protein of Bovine Papillomavirus Type 1 Interferes with E2 Protein-Mediated Tethering of the Viral DNA to Mitotic Chromosomes

2002 ◽  
Vol 76 (7) ◽  
pp. 3440-3451 ◽  
Author(s):  
Christian Voitenleitner ◽  
Michael Botchan
Keyword(s):  
Negative Regulator ◽  
Bovine Papillomavirus ◽  
Wild Type ◽  
Mitotic Chromosomes ◽  
Viral Dna ◽  
Nuclear Retention ◽  
E2 Protein ◽  
Protein Levels ◽  
E1 Protein ◽  
Dividing Cells

ABSTRACT Eukaryotic viruses can maintain latency in dividing cells as extrachromosomal plasmids. It is therefore of vital importance for viruses to ensure nuclear retention and proper segregation of their viral DNA. The bovine papillomavirus (BPV) E2 enhancer protein plays a key role in these processes by tethering the viral DNA to the host cell chromosomes. Viral genomes that harbor phosphorylation mutations in the E2 gene are transformation defective, and for these mutant genomes, neither the viral DNA nor the E2 protein is detected on mitotic chromosomes, while other key functions of E2 in transcription and replication were wild type. Moreover, secondary mutations in both the E2 and E1 proteins lead to suppression of the phosphorylation mutant phenotype and resulted in reattachment of the viral DNA and the E2 protein onto mitotic chromosomes, suggesting that E1 also plays a role in viral genome partitioning. The E1 protein was cytologically always excluded from mitotic chromatin, either as a suppressor allele or as the wild type. In the absence of other viral proteins, an E2 protein containing alanine substitutions for phosphorylation substrates in the hinge region (E2-A4) was detected as wild-type on mitotic chromosomes. However, when wild-type E1 protein levels were increased in cells expressing either the A4 mutant E2 proteins or wild-type E2, the E2-A4 protein was much more sensitive to chromosomal dislocation than was the wild-type protein. In contrast, suppressor alleles of E1 were not capable of such abrogation of E2 binding (A4 or wild-type) to chromosomes. These results suggest that wild-type E1 can be a negative regulator of the chromosomal attachment of E2.

scholarly journals INCORPORATION OF TRITIUM-LABELED THYMIDINE AND LYSINE INTO CHROMOSOMES OF CULTURED HUMAN LEUKOCYTES

1966 ◽  
Vol 29 (2) ◽  
pp. 209-222 ◽  
Author(s):  
Mac Donald Cave
Keyword(s):  
Human Leukocyte ◽  
High Rate ◽  
Chromosomal Protein ◽  
Chromosomal Dna ◽  
Mitotic Chromosomes ◽  
Daughter Cells ◽  
Temporal Relationships ◽  
Interphase Cells ◽  
Dividing Cells ◽  
S Period

The incorporation of thymidine-H3 and lysine-H3 into human leukocyte chromosomes was studied in order to determine the temporal relationships between the syntheses of chromosomal deoxyribonucleic acid and chromosomal protein. The labeled compounds were incorporated into nuclei of interphase cells. Label from both precursors became apparent over the chromosomes of dividing cells. Incorporation of thymidine-H3 occurred during a restricted period of midinterphase (S) which was preceded by a nonsynthetic period (G1) and followed by a nonsynthetic period (G2). Incorporation of lysine-H3 into chromosomal protein occurred throughout interphase. Grain counts made over chromosomes of dividing cells revealed that the rate of incorporation of lysine-H3 into chromosomal protein differed during various periods of interphase. The rate of incorporation was diminished during G1. During early S period the rate of incorporation increased, reaching a peak in late S. The high rate continued into G2. Thymidine-H3 incorporated into DNA was distributed to mitotic chromosomes of daughter cells in a manner which has been referred to as a "semi-conservative segregation." No such semi-conservative mechanism was found to affect the distribution of lysine-H3 to the mitotic chromosomes of daughter cells. Therefore, it is concluded that synthesis of chromosomal protein and its distribution to chromosomes of daughter cells are not directly influenced by synthesis and distribution of the chromosomal DNA with which the protein is associated.

Bovine Papillomavirus Type 1 Genomes and the E2 Transactivator Protein Are Closely Associated with Mitotic Chromatin

1998 ◽  
Vol 72 (3) ◽  
pp. 2079-2088 ◽  
Author(s):  
Mario H. Skiadopoulos ◽  
Alison A. McBride
Keyword(s):  
Bovine Papillomavirus ◽  
Transactivation Domain ◽  
Mitotic Chromosomes ◽  
Viral Genomes ◽  
Binding Function ◽  
Dividing Cells ◽  
Transactivator Protein ◽  
Episomal Maintenance ◽  
Mitotic Chromatin

ABSTRACT The bovine papillomavirus type 1 E2 transactivator protein is required for viral transcriptional regulation and DNA replication and may be important for long-term episomal maintenance of viral genomes within replicating cells (M. Piirsoo, E. Ustav, T. Mandel, A. Stenlund, and M. Ustav, EMBO J. 15:1–11, 1996). We have evidence that, in contrast to most other transcriptional transactivators, the E2 transactivator protein is associated with mitotic chromosomes in dividing cells. The shorter E2-TR and E8/E2 repressor proteins do not bind to mitotic chromatin, and the N-terminal transactivation domain of the E2 protein is necessary for the association. However, the DNA binding function of E2 is not required. We have found that bovine papillomavirus type 1 genomes are also associated with mitotic chromosomes, and we propose a model in which E2-bound viral genomes are transiently associated with cellular chromosomes during mitosis to ensure that viral genomes are segregated to daughter cells in approximately equal numbers.

scholarly journals Centromeric Non-Coding RNAs: Conservation and Diversity in Function

2020 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Takashi Ideue ◽  
Tokio Tani
Keyword(s):  
Chromosome Segregation ◽  
Genetic Material ◽  
Experimental Studies ◽  
Mitotic Chromosomes ◽  
Daughter Cells ◽  
Non Coding Rnas ◽  
Available Information

Chromosome segregation is strictly regulated for the proper distribution of genetic material to daughter cells. During this process, mitotic chromosomes are pulled to both poles by bundles of microtubules attached to kinetochores that are assembled on the chromosomes. Centromeres are specific regions where kinetochores assemble. Although these regions were previously considered to be silent, some experimental studies have demonstrated that transcription occurs in these regions to generate non-coding RNAs (ncRNAs). These centromeric ncRNAs (cenRNAs) are involved in centromere functions. Here, we describe the currently available information on the functions of cenRNAs in several species.

scholarly journals How herpesviruses pass on their genomes

2017 ◽  
Vol 216 (9) ◽  
pp. 2611-2613 ◽  
Author(s):  
Anna K. Serquiña ◽  
Joseph M. Ziegelbauer
Keyword(s):  
Cell Division ◽  
Host Cell ◽  
Cell Nucleus ◽  
Epstein Barr Virus ◽  
Latent Infection ◽  
Viral Genomes ◽  
Barr Virus ◽  
Daughter Cells ◽  
Cell Biol ◽  
Epstein Barr

Herpesvirus genomes exist and replicate as episomes inside the host cell nucleus during latent infection. Chiu et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201702013) find that unlike Epstein–Barr virus, which partitions viral genomes faithfully during cell division, Kaposi’s Sarcoma–associated herpesvirus clusters viral genomes into loci that are distributed unequally to daughter cells.

scholarly journals Inhibition of E2 Binding to Brd4 Enhances Viral Genome Loss and Phenotypic Reversion of Bovine Papillomavirus-Transformed Cells

2005 ◽  
Vol 79 (23) ◽  
pp. 14956-14961 ◽  
Author(s):  
Jianxin You ◽  
Michal-Ruth Schweiger ◽  
Peter M. Howley
Keyword(s):  
Viral Genome ◽  
Mitotic Chromosome ◽  
Transformed Cells ◽  
Bovine Papillomavirus ◽  
Complete Elimination ◽  
Mitotic Chromosomes ◽  
Viral Dna ◽  
Viral Genomes ◽  
Dividing Cells ◽  
Phenotypic Reversion

ABSTRACT The bovine papillomavirus E2 protein tethers the viral genomes to mitotic chromosomes in dividing cells through binding to the C-terminal domain (CTD) of Brd4. Expression of the Brd4-CTD competes the binding of E2 to endogenous Brd4 in cells. Here we extend our previous study that identified Brd4 as the E2 mitotic chromosome receptor to show that Brd4-CTD expression released the viral DNA from mitotic chromosomes in BPV-1 transformed cells. Furthermore, stable expression of Brd4-CTD enhanced the frequency of morphological reversion of BPV-1 transformed C127 cells resulting in the complete elimination of the viral DNA in the resulting flat revertants.

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