The Structure of Adenovirus Chromatin in Infected Cells

Abstract

SUMMARYThe structure of adenovirus chromatin in infected cells was studied by micrococcal nuclease digestion and hybridization with virus-specific probes. In the early phase of infection (5 h) a significant proportion of viral molecules was organized like actively transcribed cellular chromatin. As expected for a transcriptionally active population of molecules, even at high multiplicity of infection the nucleosomal repeating pattern was less distinct than in a transformed cell which contained the corresponding but less active genomic region. The observed repeating pattern in infected cells was unlikely to be due to integrated molecules since less than 0.07~ of input genomes became associated with cellular DNA. After the onset of viral DNA replication, the pool of viral chromatin organized like cellular chromatin rapidly increased. In addition, newly replicated molecules also maintained the cellular chromatin-like organization as measured by [3H]thymidine incorporation after the cessation of cellular DNA synthesis. These data suggest that newly replicated viral molecules are organized by histones into cell-like chromatin throughout the infection cycle. Coincident with the peak of viral DNA and core protein synthesis, and the decline of histone synthesis, the late, core-like non-repeating viral chromatin became dominant, increasingly obscuring the underlying repeating pattern. Experiments suggest that this late chromatin is destined for encapsidation, that the early chromatin persists and that viral core proteins do not displace histones on viral DNA. A model is proposed suggesting that transcription and type I replication occur on histone-condensed templates, while type II replication products late in infection are condensed by core proteins and are destined for encapsidation.

Adenovirus E1A: remodelling the host cell, a life or death experience

“…It has been suggested that during early Ad infection viral DNA dissociates from core proteins and that naked Ad DNA rapidly becomes chromatinized' by host cell histones (Dery et al, 1985). Transcription of viral genes has been proposed to occur from both core templates (Matsumoto et al, 1995) and cellular histone templates (Dery et al, 1985), although how this relates to primary infection in the natural host is unknown. E1A plays a signi®cant role in regulating the temporal transcription pattern of Ad genes necessary for viral replication, and also reprogramming host cell transcription to induce S phase (Shenk, 1996).…”

Assembly of Helper-Dependent Adenovirus DNA into Chromatin Promotes Efficient Gene Expression

“…However, conflicting data suggest that VII either stably associates with Ad DNA throughout the early phase of infection (9,77) or is evicted within a few hours (70), and eviction of VII may require active transcription (10). Few studies have addressed whether Ad DNA in the nucleus directly interacts with histones or assembles into chromatin; indeed, conflicting data suggest that Ad DNA is (5,13,14,66) or is not (76) assembled into chromatin. Histone H1 escorts the Ad core (Ad DNA bound to protein VII) through the nuclear pore, although this function for H1 appears independent of any role in condensing the viral DNA, and whether H1 continues to associate with the viral DNA within the nucleus is unknown (74).…”

Postinternalization Inhibition of Adenovirus Gene Expression and Infectious Virus Production in Human T-Cell Lines

“…In the case of both EBV and CMV, the viral genome is organized into chromatin by cellular histones, and the transition from latent to lytic replication is associated with the acetylation of histones covering key lytic phase promoters (35,42,45). Although one early report suggested that the adenovirus genome in infected cells might be organized into nucleosomes by cellular histones (16), others have shown that instead the adenovirus core pVII protein organizes the genome into nucleosome-like structures (11). The effect of this organization on viral transcription, and whether it is modulated similarly to cellular chromatin, is unknown.…”