Replication-Uncoupled Histone Deposition during Adenovirus DNA Replication

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Promyelocytic leukemia protein nuclear bodies (PML-NBs) are subnuclear domains implicated in cellular antiviral responses. Despite the antiviral activity, several nuclear replicating DNA viruses use the domains as deposition sites for the incoming viral genomes and/or as sites for viral DNA replication, suggesting that PML-NBs are functionally relevant during early viral infection to establish productive replication. Although PML-NBs and their components have also been implicated in the adenoviral life cycle, it remains unclear whether incoming adenoviral genome complexes target PML-NBs. Here we show using immunofluorescence and live-cell imaging analyses that incoming adenovirus genome complexes neither localize at nor recruit components of PML-NBs during early phases of infection. We further show that the viral DNA binding protein (DBP), an early expressed viral gene and essential DNA replication factor, independently targets PML-NBs. We show that DBP oligomerization is required to selectively recruit the PML-NB components Sp100 and USP7. Depletion experiments suggest that the absence of one PML-NB component might not affect the recruitment of other components toward DBP oligomers. Thus, our findings suggest a model in which an adenoviral DNA replication factor, but not incoming viral genome complexes, targets and modulates PML-NBs to support a conducive state for viral DNA replication and argue against a generalized concept that PML-NBs target incoming viral genomes. IMPORTANCEThe immediate fate upon nuclear delivery of genomes of incoming DNA viruses is largely unclear. Early reports suggested that incoming genomes of herpesviruses are targeted and repressed by PML-NBs immediately upon nuclear import. Genome localization and/or viral DNA replication has also been observed at PML-NBs for other DNA viruses. Thus, it was suggested that PML-NBs may immediately sense and target nuclear viral genomes and hence serve as sites for deposition of incoming viral genomes and/or subsequent viral DNA replication. Here we performed a detailed analyses of the spatiotemporal distribution of incoming adenoviral genome complexes and found, in contrast to the expectation, that an adenoviral DNA replication factor, but not incoming genomes, targets PML-NBs. Thus, our findings may explain why adenoviral genomes could be observed at PML-NBs in earlier reports but argue against a generalized role for PML-NBs in targeting invading viral genomes.

Section: Dbp Targets Pml-nbs and Recruits Its Components In The Absensupporting

confidence: 76%

Section: Dbp Targets Pml-nbs and Recruits Its Components In The Absenmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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An Adenovirus DNA Replication Factor, but Not Incoming Genome Complexes, Targets PML Nuclear Bodies

Komatsu

Nagata

Wodrich

2016

Self Cite

“…During herpesvirus lytic infection, the viral genomes are associated with histones immediately after injection into the nucleus, and viral proteins are required to enhance histone acetylation to allow for efficient viral gene expression (40)(41)(42)(43)(44). Moreover, studies of infection by an adenovirus have shown that viral proteins mediate the transcriptional activation of viral promoter regions (45)(46)(47). In this work, we first observed that the progress of CPV infection was accompanied by the enrichment of H3 histones in the enlarged APAR body area.…”

Section: Discussionmentioning

confidence: 62%

Promoter-Targeted Histone Acetylation of Chromatinized Parvoviral Genome Is Essential for the Progress of Infection

Mäntylä

Salokas

Oittinen

et al. 2016

The association of host histones with parvoviral DNA is poorly understood. We analyzed the chromatinization and histone acetylation of canine parvovirus DNA during infection by confocal imaging and in situ proximity ligation assay combined with chromatin immunoprecipitation and high-throughput sequencing. We found that during late infection, parvovirus replication bodies were rich in histones bearing modifications characteristic of transcriptionally active chromatin, i.e., histone H3 lysine 27 acetylation (H3K27ac). H3K27ac, in particular, was located in close proximity to the viral DNA-binding protein NS1. Importantly, our results show for the first time that in the chromatinized parvoviral genome, the two viral promoters in particular were rich in H3K27ac. Histone acetyltransferase (HAT) inhibitors efficiently interfered with the expression of viral proteins and infection progress. Altogether, our data suggest that the acetylation of histones on parvoviral DNA is essential for viral gene expression and the completion of the viral life cycle. IMPORTANCEViral DNA introduced into cell nuclei is exposed to cellular responses to foreign DNA, including chromatinization and epigenetic silencing, both of which determine the outcome of infection. How the incoming parvovirus resists cellular epigenetic downregulation of its genes is not understood. Here, the critical role of epigenetic modifications in the regulation of parvovirus infection was demonstrated. We showed for the first time that a successful parvovirus infection is characterized by the deposition of nucleosomes with active histone acetylation on the viral promoter areas. The results provide new insights into the regulation of parvoviral gene expression, which is an important aspect of the development of parvovirus-based virotherapy. N uclear chromatin is composed of DNA and histone proteins (1). The histone proteins assemble DNA into nucleosomes, the composition and spacing of which contribute to higher-order chromatin packing. The chromatin is organized into regions of less-condensed actively transcribed chromatin (euchromatin) and highly condensed transcriptionally repressed chromatin (heterochromatin). Epigenetic modifications of histone proteins have been shown to correlate with the spatial distribution of active and repressed chromatin (2, 3). The acetylation of lysine 9 or 27 of histone H3 (H3K9ac and H3K27ac, respectively) and trimethylation of lysine 4 (H3K4me3) correlate with transcriptional activity, while repressed chromatin is characterized by, e.g., trimethylation or dimethylation of the same H3 lysine residues (H3K9me3 and H3K27me3 as well as H3K9me2 and H3K27me2) (4-8).Foreign DNA introduced into mammalian cells can be recognized as a threat by the host cell. The cellular responses to the foreign DNA, such as viral DNA, include the chromatinization of the entering DNA, leading to its transcriptional silencing (9-11). How viruses resist cellular chromatinization and silencing is known for only a few viruses (9, 12, 13). These include h...

“…Since this discovery, the importance of the chromatinization of the viral genome in DNA damage (30) and transcription control (31,32) has become increasingly apparent. Previous work from our lab has further shown regulatory roles for chromatin modifications within the promoter regions of the viral genome (6).…”

Section: Discussionmentioning

confidence: 99%

Adenovirus E1A Recruits the Human Paf1 Complex To Enhance Transcriptional Elongation

Fonseca

Cohen

Mymryk

2014

During infection by human adenovirus (HAdV), the proteins encoded by the early region 1A (E1A) gene bind and appropriate components of the cellular transcriptional machinery to activate the transcription of viral early genes. Previously, we identified roles for the human Bre1 (hBre1) and hPaf1 complexes in E1A-mediated transcriptional activation of HAdV early genes. Here we show that E1A binds hBre1 directly and that this complex targets the hPaf1 complex via the Rtf1 subunit. Depletion of hPaf1 reduces E1A-dependent activation of transcription from the E2e, E3, and E4 viral transcription units, and this does not result from a reduced ability of RNA polymerase II to be recruited to the promoter-proximal regions of these genes. In contrast, depletion of hPaf1 reduces the occupancy of RNA polymerase II across these transcription units. This is accompanied by reductions in the level of H3K36 trimethylation, a posttranslational histone modification associated with efficient transcriptional elongation, and the number of full-length transcripts from these genes. Together, these results indicate that E1A uses hBre1 to recruit the hPaf1 complex in order to optimally activate viral early transcription by enhancing transcriptional elongation. IMPORTANCEThis work provides the mechanism by which the hPaf1 complex contributes to E1A-dependent activation of early gene transcription. The work also demonstrates that E1A induces gene expression by stimulating transcriptional elongation, in addition to its better-characterized effects on transcriptional initiation.