N-Myristoylation of the Rpt2 subunit of the yeast 26S proteasome is implicated in the subcellular compartment-specific protein quality control system.
Ubiquitination is the posttranslational modification of a protein by covalent attachment of ubiquitin. Controlled proteolysis via the ubiquitin-proteasome system (\UPS) alleviates cellular stress by clearing misfolded proteins. In budding yeast, UPS within the nucleus degrades the nuclear proteins as well as proteins imported from the cytoplasm. While the predominantly nuclear localization of the yeast proteasome is maintained by the importin-mediated transport, N-myristoylation of the proteasome subunit Rpt2 was indicated to cause dynamic nucleo-cytoplasmic localization of proteasomes. Here, we quantitatively analyzed the ubiquitinated peptides using anti-K-ε-GG antibody in yeast cell lines with or without a mutation in the N-myristoylation site of Rpt2 and detected upregulated ubiquitination of proteins with nucleo-cytoplasmic localizations in the mutant strains. Moreover, both the protein and ubiquitinated peptide levels of two Hsp70 family chaperones involved in the nuclear import of misfolded proteins, Ssa and Sse1, were elevated in the mutant strains, whereas levels of an Hsp70 family chaperone involved in the nuclear export, Ssb, were reduced. Taken together, our results indicate that N-myristoylation of Rpt2 is involved in controlled proteolysis via regulation of the nucleo-cytoplasmic localization of the yeast proteasome.
Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan; Graduate School of Medical Life Science, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan.
Ayuko
A
Kimura
Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan; Graduate School of Medicine, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan.
Yoichi
Y
Kurata
Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan; Graduate School of Medicine, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan.
Jun
J
Nakabayashi
Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan; Graduate School of Medical Life Science, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan.
Hiroyuki
H
Kagawa
Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan; Graduate School of Medical Life Science, Yokohama City University, Fukuura 3-9, Kanazawa, Yokohama 236-0004, Japan. Electronic address: hirano@yokohama-cu.ac.jp.
Hisashi
H
Hirano
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D013058:Mass Spectrometry; D018832:Molecular Chaperones / Q000378:metabolism; D009154:Mutation; D019814:Myristic Acid / Q000737:chemistry*; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D054875:Ubiquitination
D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; D019814:Myristic Acid; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000251:Adenosine Triphosphatases; C577243:Rpt2 protein, S cerevisiae
Cytoplasm; N-Myristoylation; Nucleus; Proteasome; Protein quality control; Ubiquitin