Gene and protein sequences of adenovirus protein VII, a hybrid basic chromosomal protein.

Abstract

The sequences of both the gene and the corresponding protein of adenovirus major core protein VII have been determined. The precise location of this gene is between 43.37 and 44.90 map coordinates on the viral genome. Protein VII is 173 residues long and has a molecular weight of 19,258. Detailed analysis of its sequence has revealed four basic domains separated by several predicted a helices. It is proposed that intrachain folding of protein VII is driven by hydrophobic interactions of the a helices, leaving the basic domains of the protein to interact with DNA phosphates. Protein monomers may further associate with each other in the formation of hexameric nucleosome-like particles. The displacement and replacement of protein VII during the viral infectious cycle in the host cell appears to mimic the biology of nucleoprotamine during the processes of spermatogenesis and fertilization. The presence of a protamine-like domain affirms a hybrid histone/protamine molecular structure for protein VII, although it may resemble the protamine in function.DNA is associated with various classes of basic proteins in the nuclei of eukaryotic cells. These proteins provide structural stability as well as functional organization of the DNA into chromosomes. As an example of the different and specific roles of the nuclear proteins, full complements of somatic histones in genetically active germ-line cells are progressively replaced by the arginine-rich protamine of mature sperm (1). During the process of fertilization, protamine is removed, histones regain their associations with the DNA, and the compact chromatin of the sperm decondenses. The "life cycles" of the two classes of basic proteins in relation to the life cycle of sperm cells indicate their distinctive interactions with DNA. Among the histones, additional distinctions can be made for their role in the structure and expression of genomic DNA.The core histones, H2a, H2b, H3, and H4, are functionally different from the spacer histone, H1 (2). Because There are 1,080 copies of core protein VII (Mr = 18,000) and 180 copies of the minor core protein V (Mr = 45,000) involved in the formation of the compact virus core (6). Micrococcal nuclease digestion of the virus core has resulted in a 150-base-pair subunit DNA fragment (7), but no nucleosome repeat pattern has been observed. As early as 3 hr after infection, intranuclear adenovirus DNA assumes a nucleosomal repeat pattern similar to that of cellular chromatin (8-11). This suggests that, during virus uncoating to produce transcriptionally active viral DNA, the adenovirus 2 specific basic proteins VII and V are replaced by histones. Viral DNA synthesis, which begins at 6 hr after infection, initiates the transcription of late genes coding for viral structural polypeptides. At the late stage of infection, progeny viral DNA once again assumes the viral chromatin structure (10). The replacement of basic nuclear proteins during the growth and development of the adenovirion appears to mimic the life cycle of histones...

Isolation and Characterization of the DNA and Protein Binding Activities of Adenovirus Core Protein V

“…Furthermore, the effects on morphology and thermostability of Ad5-dV (21) together with our results show that protein V has a strong direct association with DNA through multiple binding sites. These results suggest that protein V not only surrounds the complex of protein VII-DNA but also could be a part of the adenovirus nucleosomes (54). Protein V's ability to facilitate interactions with DNA, protein VII, and to maintain condensed core structures suggests that it has functions akin to those of histone H1.…”

“…Proteins VII and V have different associations with the viral DNA, as indicated by the selective release of protein V from the cores after a number of treatments (18,44,45). Salt-disrupted cores contain only DNA and protein VII, suggesting that protein VII is more tightly associated with viral DNA than protein V (15,54). Protein V was been suggested to be responsible for the stability and to form more condensed core structures (15,18).…”

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

“…Protein VII is a protamine-like protein and is responsible for wrapping and condensing the viral DNA in the infecting virion (39,71), and it is this protein VII-wrapped DNA that enters the nucleus (9). This highly condensed nucleoprotein structure is refractory to viral gene expression, and for wild-type Ad, preventing decondensation of the Ad nucleoprotein core reduces expression of virus-carried genes and virus replication (24).…”

Simultaneous Single-Cell In Situ Analysis of Human Adenovirus Type 5 DNA and mRNA Expression Patterns in Lytic and Persistent Infection

“…Notably, MLTU encodes an abundant histone-like protein, pVII, which is proteolytically processed into the mature protein VII during the final steps of virion maturation (13). The mature protein VII [also known as pVII(Δ24) (14)] organizes the viral genome into a nucleosome-like structure (15)(16)(17), protects viral DNA from the cellular DNA damage response (18), and also can act as a protein regulating transcription (19,20).…”