Biomedical subjects
Publications and source records attributed to J Davey.
We have isolated and sequenced the ptb1 gene from the fission yeast Schizosaccharomyces pombe. Sequence analysis suggests that Ptb1 is the beta subunit of the type-II geranylgeranyltransferase that is responsible for geranylgeranylation of the Rab-like YPT proteins in this yeast.
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Haploid cells of the fission yeast Schizosaccharomyces pombe exist in one of two mating types, referred to as M and P. Conjugation occurs between cells of opposite mating type and is controlled by the reciprocal action of diffusible pheromones. Loss of function of the sxa2 gene in M cells causes hypersensitivity to the P-factor mating pheromone and a reduction in mating efficiency. Here we demonstrate the secretion of an sxa2-dependent carboxypeptidase that inactivates P-factor by removal of the C-terminal leucine residue.
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Conjugation between two haploid yeast cells is generally controlled by the reciprocal action of diffusible mating pheromones, cells of each mating type releasing pheromones that induce mating-specific changes in cells of the opposite type. Recent studies into pheromone signalling in the fission yeast Schizosaccharomyces pombe have revealed significant parallels with processes in higher eukaryotes and could provide the opportunity for investigating communication in an organism that is amenable to both biochemical and genetic manipulation.
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The mat1 locus is a key regulator of both conjugation and meiosis in the fission yeast Schizosaccharomyces pombe. Two alternative DNA segments of this locus, mat1-P and mat1-M, specify the haploid cell types (Plus and Minus). Each segment includes two genes: mat1-P includes mat1-Pc and mat1-Pm, while mat1-M includes mat1-Mc and mat1-Mm. The mat1-Pc and mat1-Mc genes are responsible for establishing the pheromone communication system that mediates conjugation between P and M cells, while all four mat1 genes are required for meiosis in diploid P/M cells. Our understanding of the initiation of meiosis is based largely on indirect observations, and a more precise investigation of these events was required to define the interaction between the mat1 genes. Here we resolve this issue using synthetic pheromones and P/M strains with mutations in either mat1-Pc or mat1-Mc. Our results suggest a model in which the mat1 locus plays two roles in controlling meiosis. In the first instance, the mat1-Pc and mat1-Mc functions are required to produce the mating pheromones and receptors that allow the generation of a pheromone signal. This signal is required to induce the expression of mat1-Pm and mat1-Mm. This appears to be the major pheromone-dependent step in controlling meiosis since ectopic expression of these genes allows meiosis in the absence of mat1-Pc and mat1-Mc. The mat1-Pm and mat1-Mm products complete the initiation of meiosis by activating transcription of the mei3 gene.
The efficiency of modern health care relies more and more upon a computerized infrastructure. Open distributed IT-systems have started to bring professionals together from all around the world. Multimedia applications integrate formerly separated functionalities. On the one hand, easy processing and communication of images, sounds, and texts will help to represent illnesses and diseases holistically. But, on the other hand, such technology may compromise the privacy of patients, and may subvert the accountability and professional secrecy of health care professionals. The European Union has initiated a multi-disciplinary project to come up with practical guidelines on how to achieve a Secure Environment for Information Systems in MEDicine (SEISMED). It has taken into account the traditional and proven principles of health care data processing, the various legislations within the EU, the enormous and subtle risks of health care IT-systems, and the cost of changing existing technology.
The activation of pro-hormones and many precursor proteins involves cleavage by endopeptidases belonging to the subtilisin-like family of enzymes. Here we describe the isolation and characterization of the first member of this family from the fission yeast Schizosaccharomyces pombe. The enzyme, which has been named krp for KEX2-related protease, is a type I membrane-bound endopeptidase that cleaves substrates after pairs of dibasic residues. It appears to be synthesized as a pre-pro-protein that is likely to undergo processing following translocation into the endoplasmic reticulum. Processing has been characterized in a cell-free translation/translocation system prepared from Xenopus eggs. Krp is N-glycosylated on all five of its potential sites and both the pre-sequence and the pro-sequence are quickly removed following translocation, the latter probably by autocatalytic cleavage. The inhibitor profile of krp broadly reflects the known properties of the eukaryotic subtilisin proteases, while its pH and Ca2+ dependence are consistent with it being active within the secretory pathway. One of its physiological substrates is likely to be the pheromone precursor pro-P-factor, which it is shown to process in an in vitro system, but identification of other substrates is complicated because, unlike other members of this family, krp is essential for cell viability.