Herpes simplex virus type I disrupts the ATR-dependent DNA-damage response during lytic infection

The precise mechanism by which histones are loaded on herpesvirus DNA has not been elucidated; however, both viral proteins and cellular histone chaperones are likely to be involved (Ambagala et al., 2009;Cliffe and Knipe, 2008;Placek et al., 2009;Kutluay and Triezenberg, 2009;Peng et al., 2010). Wild-type HSV-1 has evolved multiple mechanisms to evade host cellular defences and the key determinant responsible for the neurovirulence of HSV-1 was mapped to the viral protein ICP34.5. An intriguing finding was that the number of Vero cells that were infected by the ICP0 mutant viruses, as judged by expression of ICP4, far exceeded the number of PFU. ICP0 is also required to stimulate lytic infection by enhancing the probability that a cell receiving a viral genome will engage in productive infection (reviewed in references 19, 20 and 42). In the latently infected cells, all viral genes except that encoding the latency-associated RNA (LAT) are turned off (reviewed in ref. ATR on the other hand, is activated by ssDNA intermediates that are generated by a variety of genotoxic assaults including those that cause replication fork perturbations. The existing antiherpesvirus drugs target lytic infection; thus, therapeutics to cure latent infections will require new antiviral strategies.

The HSV-1 DNAs in complexes fractionating as mono- to dinucleosomes were stabilized by cross-linking. Additional targets for miR-H1 and targets for a conserved family of miRNAs expressed during lytic infection will be identified. To assess the influence of dominant restrictions on the complete viral life cycle including cell entry, RNA translation, replication and virus assembly, we took advantage of a human liver cell line (Huh-7 Lunet N cells 9) which lacks endogenous expression of CD81, an essential entry factor of HCV. This barrier can be overcome by activator-mediated recruitment of transcriptional coactivators that either covalently modify histones (29, 41) or remodel the position of nucleosomes along DNA (11, 56). Genomes of DNA viruses, like their host genomes, are sub- ject to chromatin-based repression and regulation (47). The cytoskeletal framework and poliovirus metabolism. analyzed data; and Q.-Y.W., C.Z., K.E.J., R.C.C., D.M.C., and D.M.K.

To address this question, we employed chromatin immunoprecipitation (ChIP) assays to detect the presence of all four core histones on different regions of the viral genome during different stages of lytic infection. Roizman, B., Kozak, M., Honess, R. Therefore, these epigenetic targets also represent novel antiviral targets. ICP0 is also required to stimulate lytic infection by enhancing the probability that a cell receiving a viral genome will engage in productive infection (reviewed in references 19, 20 and 42). Pombo, I. The study presented here begins to uncover how the interplay between host cell repair responses and the virus’ reply to these responses contributes to forming either a genome template for replication during the productive cycle or a persistent stable configuration during latency. In this Aim, we will examine if viral binding of the cells, viral gene expression, viral replication, or all of the above were required to initiate Egr1 transcription/translation.

Three reports described global analysis of VZV transcription in cultures harvested at advanced stages of infection; Northern blot analysis of RNA extracted from late-stage VZV-infected cultures identified 58 to 67 discrete transcripts mapping throughout the virus genome (26, 32), while single-stranded DNA probes used in Northern blots revealed the direction of transcription of 57 of the 58 previously identified VZV transcripts and also identified 20 novel virus transcripts (35). Based on common control of a number of DNA viruses by epigenetic modulation, it was also demonstrated that this LSD1 inhibitor blocks initial gene expression of the human cytomegalovirus and adenovirus type 5. During latent infection the HSV-1 genome is largely compacted into inactive heterochromatin (6, 35). These dynamics reconcile the weak interactions between HSV-1 genomes and chromatin proteins, detected by nuclease protection and chromatin immunoprecipitation, with the proposed regulation of HSV-1 gene expression by chromatin, supported by the marks in the chromatin in the viral genomes and the abilities of the HSV-1 transcription activators to modulate chromatin. We conclude that the HSV-1 LATs facilitate the long-term stability of the latent cell population within the infected host and that interpretation of LAT establishment phenotypes is influenced by infection methodology. Our results suggest that HHV8 vFLIP might contribute to the persistent NF-κB activation observed in PEL cells by associating with and stimulating the activity of the cellular IKK complex. 41.

Although HSV replication has been previously thought to initiate by a theta mechanism from a circular genome template, these results suggest that HSV replication initiates from a linear genome template due to the presence of ICP0 during lytic infection. Inhibition of the activity of this enzyme results in increased repressive chromatin assembly and suppression of viral gene expression during lytic infection as well as reactivation from latency in a mouse ganglion explant model. Moreover, RNAP II and histones cooccupied the viral genome in this context, indicating that RNAP II does not preferentially associate with viral genomes that are devoid of histones.

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