The 1.5 A crystal structure of a highly selected antiviral T cell receptor provides evidence for a structural basis of immunodominance

Despite a potential repertoire of >10(15) alphabeta T cell receptors (TcR), the HLA B8-restricted cytolytic T cell response to a latent antigen of Epstein-Barr virus (EBV) is strikingly limited in the TcR sequences that are selected. Even in unrelated individuals this response is dominated by a single highly restricted TcR clonotype that selects identical combinations of hypervariable Valpha, Vbeta, D, J, and N region genes. We have determined the 1.5 A crystal structure of this "public" TcR, revealing that five of the six hypervariable loops adopt novel conformations providing a unique combining site that contains a deep pocket predicted to overlay the HLA B8-peptide complex. The findings suggest a structural basis for the immunodominance of this clonotype in the immune response to EBV.     

The discovery of Rubisco activase – yet another story of serendipity

A brief history of Rubisco (ribulose bisphosphate carboxylase oxygenase) research and the events leading to the discovery and initial characterization of Rubisco activase are described. Key to the discovery was the chance isolation of a novel Arabidopsis photosynthesis mutant. The characteristics of the mutant suggested that activation of Rubisco was not a spontaneous process in vivo, but involved a heritable factor. The search for the putative factor by 2D electrophoresis identified two polypeptides, genetically linked to Rubisco activation, that were missing in chloroplasts from the mutant. An assay for the activity of these polypeptides, which were given the name Rubisco activase, was developed after realizing the importance of including ribulose bisphosphate (RuBP) in the assay. The requirement for ATP and the subsequent identification of activase as an ATPase came about fortuitously, the result of a RuBP preparation that was contaminated with adenine nucleotides. Finally, the ability of activase to relieve inhibition of the endogenous Rubisco inhibitor, 2-carboxyarabinitol 1-phosphate, provided an early indication of the mechanism by which activase regulates Rubisco. This revised version was published online in June 2006 with corrections to the Cover Date.     

Applications of quantitative PCR in the biosafety and genetic stability assessment of biotechnology products

High throughput screening, increased accuracy and the coupling of real-time quantitative PCR (Q-PCR) to robotic set-up systems are beginning to revolutionise biotechnology. Applications of Q-PCR within biotechnology are discussed with particular emphasis on the following areas of biosafety and genetic stability testing: (a) determination of the biodistribution of gene therapy vectors in animals; (b) quantification of the residual DNA in final product therapeutics; (c) detection of viral and bacterial nucleic acid in contaminated cell banks and final products; (d) quantification of the level of virus removal in process validation viral clearance studies; (e) specific detection of retroviral RT activity in vaccines with high sensitivity; and (f) transgene copy number determination for monitoring genetic stability during production. Methods employed for Q-PCR assay validation as required in ICH Topic Q2A Validation of Analytical Methods: Definitions and Terminology (1st June 1995) are also reviewed.     

Diverse requirements for Notch signalling in mammals

The Notch signalling pathway has a central role in a wide variety of developmental processes and it is not therefore surprising that mutations in components of this pathway can cause dramatic human genetic disorders. One developmental process in which the Notch pathway is involved at multiple levels is somitogenesis, the mechanism by which the embryo is divided into segments that ultimately form structures such as the axial skeleton and skeletal muscle of the trunk. We are investigating the human genetic disorder spondylocostal dysplasia (SCD), which is a group of malsegmentation syndromes that occur when this process is disrupted. Mutations in the Notch ligand DELTA-LIKE 3 (DLL3) are responsible for cases of autosomal recessive SCD type I (SCDO1), and we are using information derived from these mutations to study the structure of the DLL3 protein. To aid in elucidation of the underlying developmental defect in SCDO1, we have generated a mouse model by targeted deletion of the Dll3 gene (Dunwoodie et al., 2002). These mice show segmentation defects similar to those seen in SCDO1. In addition, these mice have a distinct set of neural defects that may be useful in future neurological assessment of affected individuals. Finally, since not all cases of SCD are due to mutation of DLL3, we are investigating various genes to find other candidates involved in this genetic disease.