Replication-Uncoupled Histone Deposition during Adenovirus DNA Replication

Department of Infection Biology, Faculty of Medicine and Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan.
Journal of Virology (Impact Factor: 4.44). 04/2012; 86(12):6701-11. DOI: 10.1128/JVI.00380-12
Source: PubMed

ABSTRACT In infected cells, the chromatin structure of the adenovirus genome DNA plays critical roles in its genome functions. Previously, we reported that in early phases of infection, incoming viral DNA is associated with both viral core protein VII and cellular histones. Here we show that in late phases of infection, newly synthesized viral DNA is also associated with histones. We also found that the knockdown of CAF-1, a histone chaperone that functions in the replication-coupled deposition of histones, does not affect the level of histone H3 bound on viral chromatin, although CAF-1 is accumulated at viral DNA replication foci together with PCNA. Chromatin immunoprecipitation assays using epitope-tagged histone H3 demonstrated that histone variant H3.3, which is deposited onto the cellular genome in a replication-independent manner, is selectively associated with both incoming and newly synthesized viral DNAs. Microscopic analyses indicated that histones but not USF1, a transcription factor that regulates viral late gene expression, are excluded from viral DNA replication foci and that this is achieved by the oligomerization of the DNA binding protein (DBP). Taken together, these results suggest that histone deposition onto newly synthesized viral DNA is most likely uncoupled with viral DNA replication, and a possible role of DBP oligomerization in this replication-uncoupled histone deposition is discussed.

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    • "In ChIP-based studies, hdAd, E1-deleted Ad [76] and wtAd [77] DNA associates with H3.3 as early as four hours post-infection, which suggests a replication-independent mechanism is responsible for the assembly of chromatin on Ad DNA. Recent work by Komatsu et al. [77] showing that knocking down of CAF-1 does not affect histone deposition on the Ad genome supports this idea [77]. Knockdown of HIRA reduced association of the hdAd DNA with H3, and also reduced Ad-mediated transgene expression [76], suggesting that assembly into chromatin is required for optimal gene expression. "
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    ABSTRACT: Vectors based on adenovirus (Ad) are one of the most commonly utilized platforms for gene delivery to cells in molecular biology studies and in gene therapy applications. Ad is also the most popular vector system in human clinical gene therapy trials, largely due to its advantageous characteristics such as high cloning capacity (up to 36 kb), ability to infect a wide variety of cell types and tissues, and relative safety due to it remaining episomal in transduced cells. The latest generation of Ad vectors, helper‑dependent Ad (hdAd), which are devoid of all viral protein coding sequences, can mediate high-level expression of a transgene for years in a variety of species ranging from rodents to non-human primates. Given the importance of histones and chromatin in modulating gene expression within the host cell, it is not surprising that Ad, a nuclear virus, also utilizes these proteins to protect the genome and modulate virus- or vector‑encoded genes. In this review, we will discuss our current understanding of the contribution of chromatin to Ad vector function.
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    • "The histones must therefore be displaced from the Ad DNA and replaced with pre-protein VII, the precursor of the mature protein VII. Reduced association of histones with the Ad DNA is thought to occur either passively, as the cellular stores of histones decline during the course of infection, or actively through exclusion of histones from the viral replication centers by the Ad-encoded DNA binding protein (DBP) (Komatsu and Nagata, 2012). Based on several lines of evidence, it has been suggested that TAF-III/nucleophosmin may be involved in placing pre-protein VII on the viral DNA (Samad et al., 2012). "
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    ABSTRACT: Like their cellular host counterparts, many invading viral pathogens must contend with, modulate, and utilize the host cell's chromatin machinery to promote efficient lytic infection or control persistent-latent states. While not intended to be comprehensive, this review represents a compilation of conceptual snapshots of the dynamic interplay of viruses with the chromatin environment. Contributions focus on chromatin dynamics during infection, viral circumvention of cellular chromatin repression, chromatin organization of large DNA viruses, tethering and persistence, viral interactions with cellular chromatin modulation machinery, and control of viral latency-reactivation cycles.
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    ABSTRACT: The expression of adenovirus late genes is shown to require viral DNA replication, but its mechanism remains elusive. Here we found that knockdown of CTCF suppresses viral DNA replication as well as late, but not early, gene expression. Chromatin immunoprecipitation assays indicated that CTCF binds to viral chromatin depending on viral DNA replication. These findings depict CTCF as a critical regulator for adenovirus genome functions in late phases of infection.
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