Proteasome nuclear activity affects chromosome stability by controlling the turnover of Mms22, a protein important for DNA repair.
To expand the known spectrum of genes that maintain genome stability, we screened a recently released collection of temperature sensitive (Ts) yeast mutants for a chromosome instability (CIN) phenotype. Proteasome subunit genes represented a major functional group, and subsequent analysis demonstrated an evolutionarily conserved role in CIN. Analysis of individual proteasome core and lid subunit mutations showed that the CIN phenotype at semi-permissive temperature is associated with failure of subunit localization to the nucleus. The resultant proteasome dysfunction affects chromosome stability by impairing the kinetics of double strand break (DSB) repair. We show that the DNA repair protein Mms22 is required for DSB repair, and recruited to chromatin in a ubiquitin-dependent manner as a result of DNA damage. Moreover, subsequent proteasome-mediated degradation of Mms22 is necessary and sufficient for cell cycle progression through the G(2)/M arrest induced by DNA damage. Our results demonstrate for the first time that a double strand break repair protein is a proteasome target, and thus link nuclear proteasomal activity and DSB repair.
Ben-Aroya
Shay
S
Michael Smith Laboratories, University of British Columbia, Vancouver, Canada.
Agmon
Neta
N
Yuen
Karen
K
Kwok
Teresa
T
McManus
Kirk
K
Kupiec
Martin
M
Hieter
Philip
P
D000483:Alleles; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology*; D002843:Chromatin / Q000378:metabolism; D043171:Chromosomal Instability; D044842:Cullin Proteins / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D015966:Gene Expression Regulation, Fungal; D020043:Genes, Essential; D006801:Humans; D007700:Kinetics; D009154:Mutation / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination
D002843:Chromatin; D044842:Cullin Proteins; C497133:Mms22 protein, S cerevisiae; D021122:Protein Subunits; C476451:RTT101 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex