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A R Hall

Publications and source records attributed to A R Hall.

11 recordsLinked to original sources
PubMed1998

p53-dependent cell death/apoptosis is required for a productive adenovirus infection.

The p53 tumor suppressor protein binds to both cellular and viral proteins, which influence its biological activity. One such protein is the large E1b tumor antigen (E1b58kDa) from adenoviruses (Ads), which abrogates the ability of p53 to transactivate various promoters. This inactivation of p53 function is believed to be the mechanism by which E1b58kDa contributes to the cell transformation process. Although the p53-E1b58kDa complex occurs during infection and is conserved among different serotypes, there are limited data demonstrating that it has a role in virus replication. However, loss of p53 expression occurs after adenovirus infection of human cells and an E1b58kDa deletion mutant (Onyx-015, also called dl 1520) selectively replicates in p53-defective cells. These (and other) data indicate a plausible hypothesis is that loss of p53 function may be conducive to efficient adenovirus replication. However, wild-type (wt) Ad5 grows more efficiently in cells expressing a wt p53 protein. These studies indicate that the hypothesis may be an oversimplification. Here, we show that cells expressing wt p53, as well as p53-defective cells, allow adenovirus replication, but only cells expressing wt p53 show evidence of virus-induced cytopathic effect. This correlates with the ability of adenovirus to induce cell death. Our data indicate that p53 plays a necessary part in mediating cellular destruction to allow a productive adenovirus infection. In contrast, p53-deficient cells are less sensitive to the cytolytic effects of adenovirus and as such raise questions about the use of E1b58kDa-deficient adenoviruses in tumor therapy.

Adenoviruses, Human↗
PubMed1997

p53/E1b58kDa complex regulates adenovirus replication.

We have explored a role for the adenovirus (Ad5) E1b58kDa/p53 protein complex in adenovirus replication. This was done by using virus mutants containing different defects in the E1b58kDa gene and cell lines that express either a wild-type p53 protein or a mutant p53 protein. We find that infection of wild-type p53-containing cells with wild-type Ad5 causes a shutoff of p53 and alpha-actin protein synthesis by distinct mechanisms, but neither occurs in mutant p53 cells. Our data also indicate that the shutoff is dependent on formation of the p53/E1b complex and may also involve another virus protein, E4ORF6. Following from these observations we asked whether failure to form the complex resulted in impaired adenovirus replication. Our experiments showed that neither wild-type Ad5 nor the E1b mutant dl338 could replicate in cells expressing a mutant p53 protein, but that wild-type adenovirus replicated well in wild-type p53-expressing cells. Collectively, our data suggest that the interaction between p53 and the E1b58kDa protein is necessary for efficient adenovirus replication. This is the first time such a direct link between the complex and virus replication has been demonstrated. These data raise serious questions about the usefulness of E1b-defective viruses in tumor therapy.

Adenoviridae↗
PubMed1997

Specific p53-DNA complexes contain an mdm2-related protein.

The mdm2 gene encodes a family of proteins, a subset of which bind p53 and negatively regulate its function as a transcription factor. We now show that an anti-mdm-2 monoclonal antibody, 2A10, recognises a protein present in rabbit reticulocyte lysate which binds murine p53 translated in vitro. Deletion of p53 residues 10-35, which encompass the mdm-2 binding site, abolished binding of this 2A10-reactive protein. Binding was also dependent upon p53 protein conformation and may require nascent p53 polypeptide since binding was lost following conformational shifting of the temperature-sensitive mutant A135V. Previous studies have shown that mdm-2-p53 complexes fail to exhibit detectable sequence-specific DNA binding. However, our present results demonstrate that p53 in complex with an mdm-2-related protein in vitro retained sequence-specific DNA binding capacity. Non-transformed (but not transformed) 3T3 cells were also found to express a similar 2A10-reactive protein, detectable by gel shift analysis of cellular p53 in complex with a specific DNA target. Mdm-2 in rabbit reticulocyte lysate and in normal, non-transformed 3T3 cells may represent constitutively expressed protein. Our results raise the possibility that constitutive mdm-2 may enhance and/or suppress functions of p53 as yet unidentified.

3T3 Cells↗
PubMed1995

Purification, characterization, synthesis, and cloning of the lockjaw peptide from Conus purpurascens venom.

The major groups of Conus peptides previously characterized from fish-hunting cone snail venoms (the alpha-, mu-, and omega-conotoxins) all blocked neuromuscular transmission. A novel activity, the "lockjaw peptide", from the fish-hunting Conus purpurascens, caused a rigid (instead of flaccid) paralysis in fish and increased excitability at the neuromuscular junction (instead of a block). We report the purification, biological activity, biochemical and preliminary physiological characterization, and chemical synthesis of the lockjaw peptide and the sequence of a cDNA clone encoding its precursor. Taken together, the data lead us to conclude that the lockjaw peptide is a vertebrate-specific delta-conotoxin, which targets voltage-sensitive sodium channels. The sequence of the peptide, which we designate delta-conotoxin PVIA, is (O = 4-trans-hydroxyproline) EACYAOGTFCGIKOGLCCSEFCLPGVCFG-NH2. This is the first of a diverse spectrum of Conus peptides which are excitotoxins in vertebrate systems.

Action Potentials↗
PubMed1995

Structural and kinetic analysis of p53-DNA complexes and comparison of human and murine p53.

Sequence-specific DNA binding by p53 is dependent upon protein conformation. The 1620+ form correlates with wild type p53 suppressor function and is a prerequisite for binding to the DNA consensus p53-CON in vitro. It has been reported that murine p53 changes conformation on interaction with high affinity DNA target sequences and in the present study we have analysed p53-DNA complexes using conformation-specific monoclonal antibodies against p53. For murine p53 (mp53) we show (i) the 1620+ form is retained and stabilised in complex with DNA, and (ii) the complexes are dissociated by the PAb1620 monoclonal antibody. In contrast, PAb1620 did not detect nor dissociate human p53-DNA complexes nor did it interfere with complex formation. In competition experiments murine p53 replaced human p53 (hp53) in p53-DNA complexes and this correlated with the greater lability observed for hp53-DNA complexes at a given temperature. Mixed human-murine p53 oligomers were competent for DNA binding with an estimated affinity around 5 x 10(-10) M, similar to that observed for either human or murine p53 alone. The potential significance of these observations is discussed in relation p53 function in vivo.

Animals↗
PubMed1980

Late Pleistocene deposits at Wing, Rutland.

The context, lithostratigraphy and biostratigraphy of a series of Pleistocene deposits from Wing, Rutland, in the East Midlands of England are described. The sequence of till, lake clays, compressed wood and moss peats and peaty silts is shown to occupy a small, closed basin cut deeply into the Jurassic bedrock. The basin appears to have been excavated by ice responsible for the deposition of Chalky Jurassic Till in the area, and this till lines the floor and sides of the basin. Pollen and plant macrofossil analyses have provided a long and continuous record of vegetational and environmental history at the site and the deposits have been dated by pollen analysis to the Last (Ipswichian) Interglacial and early Devensian Glacial stages (pollen zones Ip IIb to e De). With certain reservations, the sequence is compared and correlated with other interglacial deposits in Britain.

England↗