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The Pep4p vacuolar proteinase contributes to the turnover of oxidized proteins but PEP4 overexpression is not sufficient to increase chronological lifespan in Saccharomyces cerevisiae

¹ IBMC, Instituto de Biologia Molecular e Celular, Grupo de Microbiologia Celular e Aplicada, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal
² ICBAS, Instituto de Ciências Biomédicas Abel Salazar, Departamento de Biologia Molecular, Universidade do Porto, Porto, Portugal
³ Department of Cell and Molecular Biology, Göteborg University, Box 462, S-405 30 Göteborg, Sweden

Correspondence
Vítor Costa
vcosta{at}ibmc.up.pt

Turnover of damaged molecules is considered to play a key role in housekeeping of cells exposed to oxidative stress, and during the progress of ageing. In this work, global changes in the transcriptome were analysed during recovery of yeast cells after H₂O₂ stress. Regarding induced genes, those associated with protein fate were the most significantly over-represented. In addition to genes encoding subunits of the 20S proteasome, genes related to vacuolar proteolysis (PEP4 and LAP4), protein sorting into the vacuole, and vacuolar fusion were found to be induced. The upregulation of PEP4 gene expression was associated with an increase in Pep4p activity. The induction of genes related to proteolysis was correlated with an increased protein turnover after H₂O₂-induced oxidation. Furthermore, protein degradation and the removal of oxidized proteins decreased in Pep4p-deficient cells. Pep4p activity also increased during chronological ageing, and cells lacking Pep4p displayed a shortened lifespan associated with higher levels of carbonylated proteins. PEP4 overexpression prevented the accumulation of oxidized proteins, but did not increase lifespan. These results indicate that Pep4p is important for protein turnover after oxidative damage; however, increased removal of oxidized proteins is not sufficient to enhance lifespan.

The data from this study have been deposited in the microarray data public repository ArrayExpress under the accession number E-MEXP-326.

A summary of genes differentially expressed during the recovery of yeast cells from H₂O₂ stress is available as supplementary data with the online version of this paper.

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