Informational suppressor alleles of the eEF1A gene, fertility and cell degeneration in Podospora anserina.

Mutations that increase readthrough at a UGA stop codon (informational suppressor mutations) were created in the gene (AS4) that encodes translation elongation factor eEF1A in the filamentous fungus Podospora amserina. The results strongly suggest that the net charge of the eEF1A protein controls the accuracy of translation. Physiological analysis of the mutant strains shows that some of the alleles dominantly increase life span, while only one drastically modifies fertility. This exceptional allele (AS4-56) causes a wide array of phenotypes, including a new growth cessation phenomenon that is different from Senescence or Crippled Growth, previously known degenerative syndromes that are both controlled by AS4. The data emphasise the fact that eEF1A exerts a complex control over cellular physiology.

Deletion and dosage modulation of the eEF1A gene in Podospora anserina: effect on the life cycle.

eEF1A is encoded by a unique gene in the filamentous fungus Podospora anserina. We show here that (1) this gene is essential for vegetative growth, (2) readthrough at UGA stop codon level is positively correlated with eEF1A level, (3) eEF1A level is regulated in P. anserina. (4) Increasing eEF1A gene dosage does not modify P. anserina life cycle parameters, especially longevity is not changed. These data confirm and extend those previously obtained in yeast and Drosophila.

A Plasmodium falciparum aminopeptidase gene belonging to the M1 family of zinc-metallopeptidases is expressed in erythrocytic stages.

A new single copy gene has been isolated from Plasmodium falciparum, by immunoscreening a genomic DNA expression library. The gene appears devoid of introns, displays the classical A + T richness and codon usage of P. falciparum genes, and is transcribed into a 4 kb mRNA in erythrocytic stages. The deduced amino acid sequence corresponds to a 1056 residue protein (122 kDa) containing the canonical HExxHx18E signature of zinc-metallopeptidase active sites of the M1 family at position 467-490, a downstream conserved tyrosine residue involved in catalysis in position 551, and the GAMEN conserved motif characteristic of aminopeptidases in the M1 family, at position 431-435. The greatest similarities were found with aminopeptidases N of Escherichia coli and Haemophilius influenza (more than 80% identical residues in the canonical signature of the active site) but significant similarities centred on the active site region exist with all other members of the M1 family such as other prokaryotic aminopeptidases, eukaryotic aminopeptidases A and N and leukotriene A4 hydrolases (40-50% identical residues in the canonical signature of the active site). A polyclonal serum raised to a synthetic peptide deduced from the gene labelled schizont proteins of 96 and 68 kDa purified to homogeneity and both displaying aminopeptidase activity, as well as cytoplasmic structures in schizont stages.