W. C. Russell

Update on adenovirus and its vectors

IP: 54.70.40.11 On: Thu, 03 Jan 2019 17:11:19 Journal of General Virology (2000), 81, 2573–2604. Printed in Great Britain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Adenoviruses: update on structure and function.

Adenoviruses have been studied intensively for over 50 years as models of virus-cell interactions and latterly as gene vectors. With the advent of more sophisticated structural analysis techniques the disposition of most of the 13 structural proteins have been defined to a reasonable level. This review seeks to describe the functional properties of these proteins and shows that they all have a part to play in deciding the outcome of an infection and act at every level of the viruss path through the host cell. They are primarily involved in the induction of the different arms of the immune system and a better understanding of their overall properties should lead to more effective ways of combating virus infections.

The splicing factor‐associated protein, p32, regulates RNA splicing by inhibiting ASF/SF2 RNA binding and phosphorylation

The cellular protein p32 was isolated originally as a protein tightly associated with the essential splicing factor ASF/SF2 during its purification from HeLa cells. ASF/SF2 is a member of the SR family of splicing factors, which stimulate constitutive splicing and regulate alternative RNA splicing in a positive or negative fashion, depending on where on the pre‐mRNA they bind. Here we present evidence that p32 interacts with ASF/SF2 and SRp30c, another member of the SR protein family. We further show that p32 inhibits ASF/SF2 function as both a splicing enhancer and splicing repressor protein by preventing stable ASF/SF2 interaction with RNA, but p32 does not block SRp30c function. ASF/SF2 is highly phosphorylated in vivo, a modification required for stable RNA binding and protein–protein interaction during spliceosome formation, and this phosphorylation, either through HeLa nuclear extracts or through specific SR protein kinases, is inhibited by p32. Our results suggest that p32 functions as an ASF/SF2 inhibitory factor, regulating ASF/SF2 RNA binding and phosphorylation. These findings place p32 into a new group of proteins that control RNA splicing by sequestering an essential RNA splicing factor into an inhibitory complex.

Interaction between Herpes Simplex Virus Type 1 IE63 Protein and Cellular Protein p32

ABSTRACT The herpes simplex virus type 1 (HSV-1) immediate-early gene IE63 (ICP27), the only HSV-1 regulatory gene with a homologue in every mammalian and avian herpesvirus sequenced so far, is a multifunctional protein which regulates transcriptional and posttranscriptional processes. One of its posttranscriptional effects is the inhibition of splicing of viral and cellular transcripts. We previously identified heterogeneous nuclear ribonucleoprotein (hnRNP) K and casein kinase 2 (CK2) as two protein partners of IE63 (H. Bryant et al., J. Biol. Chem. 274:28991–28998, 1999). Here, using a yeast two-hybrid assay, we identify another partner of IE63, the cellular protein p32. Confirmation of this interaction was provided by coimmunoprecipitation from virus-infected cells and recombinant p32 binding assays. A p32-hnRNP K-CK2 complex, which required IE63 to form, was isolated from HSV-1-infected cells, and coimmunoprecipitating p32 was phosphorylated by CK2. Expression of IE63 altered the cytoplasmic distribution of p32, with some now colocalizing with IE63 in the nuclei of infected and transfected cells. As p32 copurifies with splicing factors and can inhibit splicing, we propose that IE63 together with p32, possibly with other IE63 partner proteins, acts to disrupt or regulate pre-mRNA splicing. As well as contributing to host cell shutoff, this effect could facilitate splicing-independent nuclear export of viral transcripts.

Adenovirus protein-protein interactions: molecular parameters governing the binding of protein VI to hexon and the activation of the adenovirus 23K protease

A variety of recombinant proteins derived from protein pVI of human adenovirus type 2 (Ad2) were analysed for their ability to bind Ad2 hexon in vitro. As pVI is also required for activation of the adenovirus-coded protease, the same pVI derivatives were assessed for their ability to activate recombinant adenovirus-coded 23K protease. Two regions, between amino acid residues 48-74 and 233-239 of pVI, were required for the interaction with hexon. These regions are highly conserved amongst mastadenovirus pVI proteins. Both these regions are capable on their own of binding hexon weakly but must be provided in cis for strong hexon binding. In addition, we found evidence to indicate than conformation as well as sequence was important for good hexon binding in our assays. Authentic processing of the appropriate recombinant pVI derivatives, by the recombinant protease, was obtained without the addition of other cofactors. These findings are discussed in relation to the role of pVI in triggering the adenovirus maturation pathway.

Adenovirus protein-protein interactions: hexon and protein VI

A variety of mastadenoviruses were denatured, their polypeptides separated by electrophoresis on SDS-polyacrylamide gels and transferred to nitrocellulose. The immobilized polypeptides were washed, incubated with buffers containing hexons from human adenoviruses (Ad) types 2, 5 and 12 and the location of bound hexons was detected with anti-hexon antibodies. It was found that hexons from any of the three human adenovirus types bound to protein VI from all the mastadenoviruses examined. Furthermore we found that hexon-VI binding was significantly greater than the interaction between hexon and the precursor to VI, pVI. This binding was susceptible to detergents and to changes in pH or salt concentration. A rabbit polyclonal antibody was raised against a recombinant protein derived from the middle third of pVI from Ad2 and was used to quantify the difference in binding and to demonstrate the presence of a single intermediate (designated iVI) in the processing of pVI to VI. The affinity between iVI and hexon was considerably greater in our assay than that of pVI but was less than that between hexon and VI. A complementary binding of recombinant iVI to immobilized hexons was also demonstrated. This latter interaction, however, was only observed when hexon preparations were not boiled prior to electrophoresis, substantiating the proposition that the recognition motif on the hexon was conformation-dependent. These results are discussed in the context of understanding further the molecular basis of protein-protein interactions between the structural proteins of adenoviruses and the factors involved in virion maturation.

An epitope on the adenovirus fibre tail is common to all human subgroups

Summary. A group specific linear epitope with the sequence -FNPVY- was detected in the tail region of the adenovirus fibre by using a monoclonal antibody (Mab) and selection with a hexapeptide phage expression library. A synthetic peptide with sequence DTYDTE from adenovirus type 2 (Ad2) was shown by preincubation with the Mab to block its binding to fibre. A biotinylated form of this peptide bound to the monomeric fibre and not to the dimeric and trimeric forms. On the other hand the monoclonal antibodies bound to the monomeric, dimeric and trimeric forms of the fibre.

Role of Adenovirus Structural Components in the Regulation of Adenovirus Infection

Adenoviruses contain at least 15–16 proteins in a complex assembly with the virus double-stranded genomic DNA. The disposition of the major proteins in the structure has been assigned primarily on the basis of scrutiny of the morphological features of the virus as demonstrated by electron microscopy (Valentine and Pereira 1965), by cross-linking studies (Everitt et al. 1975; Chatterjee et al. 1985) and more recently by the technique of difference imaging, which utilises the results obtained by high-resolution X-ray crystallography of the major capsid protein, the hexon, to reveal the probable location of the minor capsid proteins (Stewart et al. 1991, 1993). However, detailed knowledge of the arrangement of proteins within the capsid and their relationship to the virus genome is still rather rudimentary.

Nuclear perturbations following adenovirus infection

Adenoviruses are processed and assembled in the nuclei of infected cells and thereby produce significant perturbations to their structure and function. As the complex interactions that occur in the nuclei of uninfected cells are not yet fully understood many of the changes seen on infection have been described mainly in morphological terms. This chapter attempts to place more recent findings into this context and demonstrates that adenoviruses are able to hijack many cellular processes and enzymes to their advantage. In particular, modifications to nuclear PODs and nucleoli have more recently been explored in greater detail.