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We subjected methanol-grown cells of wild type Hansenula polymorpha simultaneously to nitrogen depletion and excess glucose conditions. Both treatments induce the degradation of peroxisomes, either selective (via excess glucose) or non-selective (via nitrogen limitation). Our combined data strongly suggest that both processes occur simultaneously under these conditions. The implications of these findings on studies of autophagy and related transport pathways to the vacuole in yeast are discussed. [Copyright &y& Elsevier]

Saccharomyces cerevisiae contains three dynamin-related-proteins, Vps1p, Dnm1p and Mgm1p. Previous data from glucose-grown VPS1 and DNM1 null mutants suggested that Vps1p, but not Dnm1p, plays a role in regulating peroxisome abundance. Here we show that deletion of DNM1 also results in reduction of peroxisome numbers. This was not observed in glucose-grown dnm1 cells, but was evident in cells grown in the presence of oleate. Similar observations were made in cells lacking Fis1p, a protein involved in Dnm1p function. Fluorescence microscopy of cells producing Dnm1-GFP or GFP-Fis1p demonstrated that both proteins had a dual localization on mitochondria and peroxisomes. Quantitative analysis revealed a greater reduction in peroxisome number in oleate-induced vps1 cells relative to dnm1 or fis1 cells. A significant fraction of oleate-induced vps1 cells still contained two or more peroxisomes. Conversely, almost all cells of a dnm1 vps1 double-deletion strain contained only one, enlarged peroxisome. This suggests that deletion of DNM1 reinforces the vps1 peroxisome phenotype. Time-lapse imaging indicated that during budding of dnm1 vps1 cells, the single peroxisome present in the mother cell formed long protrusions into the developing bud. This organelle divided at a very late stage of the budding process, possibly during cytokinesis. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies in Penicillium chrysogenum and Aspergillus nidulans suggested that self-processing of the isopenicillin N acyltransferase (IAT) is an important differential factor in these fungi. Expression of a mutant penDE C103S gene in P. chrysogenum gave rise to an unprocessed inactive variant of IAT (IATC103S) located inside peroxisomes, which indicates that transport of the proIAT inside these organelles is not dependent on the processing state of the protein. Co-expression of the penDE C103S and wild-type penDE genes in P. chrysogenum (Wis54-DE C103S strain) led to a decrease in benzylpenicillin levels. Changes in the wild-type IAT processing profile (β subunit formation) were observed in the Wis54-DE C103S strain, suggesting a regulatory role of the unprocessed IATC103S in the processing of the wild-type IAT. This was confirmed in Escherichia coli, where a delay in the processing of IAT in presence of the unprocessable IAT C103S was observed. Our results indicate that IAT is post-translationally regulated by its preprotein, which interferes with the self-processing. [Copyright &y& Elsevier]