A three-base-pair deletion in the peripherin-RDS gene in one form of retinitis pigmentosa.

The group of retinopathies termed retinitis pigmentosa (RP) greatly contribute to visual dysfunction in man with a frequency of roughly 1 in 4,000. We mapped the first autosomal dominant RP (adRP) gene to chromosome 3q, close to the gene encoding rhodopsin, a rod photoreceptor pigment protein. Subsequently, mutations in this gene have been implicated as responsible for some forms of adRP. Another adRP gene has been mapped to chromosome 8p. A third adRP gene in a large Irish pedigree has been mapped to chromosome 6p, showing tight linkage with the gene for peripherin, a photoreceptor cell-specific glycoprotein, which is thus a strong candidate for the defective gene. We have now identified a three-base-pair deletion which results in the loss of one of a pair of highly conserved cysteine residues in the predicted third transmembrane domain of peripherin. This deletion segregates with the disease phenotype but is not present in unaffected controls, and suggests that mutant peripherin gives rise to retinitis pigmentosa.     

Membrane protein association by potential intramembrane charge pairs.

The transmembrane domain of the alpha chain of the T-cell receptor is responsible both for its assembly with the CD3 delta chain and for rapid degradation of the unassembled chain within the endoplasmic reticulum. The determinant for both assembly and degradation is located in a segment of eight residues containing two basic amino acids. We show here that placement of a single basic residue in the transmembrane domain of the Tac antigen can induce interaction with the CD3 chain, through its transmembrane acidic residue. This interaction is most favoured when the interacting residues are located at the same level in the membrane. The ability to induce protein-protein interaction by placing charge pairs within transmembrane domains suggests an approach to producing artificial dimers.     

High-affinity NGF binding requires coexpression of the trk proto-oncogene and the low-affinity NGF receptor.

Nerve growth factor (NGF) interacts with two different low-affinity receptors that can be distinguished by affinity crosslinking. Reconstitution experiments by membrane fusion and transient transfection into heterologous cells indicate that high-affinity NGF binding requires coexpression and binding to both the low-affinity NGF receptor and the tyrosine kinase trk gene product. These studies reveal a new growth factor receptor-mediated mechanism of cellular differentiation involving trk and the low-affinity NGF receptor.     

Rapid spread of an inherited incompatibility factor in California Drosophila

In Drosophila simulans in California, an inherited cytoplasmic incompatibility factor reduces egg hatch when infected males mate with uninfected females. The infection is spreading at a rate of more than 100 km per year; populations in which the infection was rare have become almost completely infected within three years. Analyses of the spread using estimates of selection in the field suggest dispersal distances far higher than those found by direct observation of flies. Hence, occasional long-distance dispersal, possibly coupled with local extinction and recolonization, may be important to the dynamics. Incompatibility factors that can readily spread through natural populations may be useful for population manipulation and important as a post-mating isolating mechanism.     

Biodegradation of refractory hydrocarbon biomarkers from petroleum under laboratory conditions

Biomarkers are of great value in petroleum exploration because they provide essential information about the geological history of oils and source rocks. Steranes are of particular importance as they can be related to naturally occurring precursors. These compounds generally experience intense biodegradation, however, which alters their original distribution and obscures the information that they carry regarding oil maturity and source material. In an attempt to identify the microorganisms responsible for this degradation, we have investigated the capacity of 73 aerobic bacteria to degrade steranes present in Rozel Point (Utah) oil. Seven Gram-positive strains, belonging to a limited number of genera, were found to be active. Using Nocardia sp. SEBR 16, which caused the most extensive alteration, we have determined biodegradation rates for several isomers of steranes and methylsteranes. The preference for alteration of different isomers reflects that observed in natural environments, suggesting that the degradation intermediates could be used as indicators of the extent of the biodegradation in an oil. In addition, the microorganisms used here might be effective in biodegrading oil spills.     

A homologue of the bacterial heat-shock gene DnaJ that alters protein sorting in yeast

Heat-shock proteins have been implicated in assembly of protein complexes, correct protein folding and uptake of proteins into organelles. In Escherichia coli, the heat-shock protein DnaJ and the Hsp70 homologue, DnaK, act together to disassemble a protein complex involved in bacteriophage lambda replication. We report the identification of SCJ1, a gene in the yeast Saccharomyces cerevisiae that encodes a homologue of the bacterial DnaJ protein. SCJ1 was identified by a genetic screen in which increased expression of candidate genes results in missorting of a nuclear-targeted test protein. The predicted amino-acid sequence of SCJ1 is 37% identical to the entire E. coli DnaJ protein. Hybridization experiments indicate that there is a family of yeast genes related to SCJ1. These findings suggest that the Hsp70 DnaK-DnaJ interaction is general to eukaryotes.     

New use of BCG for recombinant vaccines

BCG, a live attenuated tubercle bacillus, is the most widely used vaccine in the world and is also a useful vaccine vehicle for delivering protective antigens of multiple pathogens. Extrachromosomal and integrative expression vectors carrying the regulatory sequences for major BCG heat-shock proteins have been developed to allow expression of foreign antigens in BCG. These recombinant BCG strains can elicit long-lasting humoral and cellular immune responses to foreign antigens in mice.     

A pseudoknot-like structure required for efficient self-cleavage of hepatitis delta virus RNA

Hepatitis delta virus genomic and antigenomic RNAs contain a self-cleavage site hypothesized to function in processing the viral RNA during replication. Self-cleavage requires only a divalent cation and is mediated at the genomic site by a sequence of less than 85 nucleotides. We propose that the genomic self-cleaving sequence element and a corresponding sequence from the anti-genomic RNA could generate related secondary structures. The region of the antigenomic sequence, predicted from the proposed structure, was synthesized and shown to be sufficient for self-cleavage. Evidence for two stems which form a tertiary interaction was obtained by site-specific mutagenesis of the antigenomic sequence. Efficient self-cleavage in 10 M formamide or 5 M urea, also a property of the genomic sequence, was dependent on base-pairing in both stems. But in the absence of denaturants, the stem distal to the site of cleavage was not required, suggesting that the tertiary interaction stabilizes the structure required for self-cleavage.