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In human cells, SUMO2 is predominantly conjugated to target proteins in response to cellular stress. Previous studies suggested that proteins conjugated to SUMO2, but not to SUMO1, could be regulated by the ubiquitin-mediated proteasome system. Hence, we set out to understand the role of the proteasome in determining the fate of proteins conjugated to SUMO2 when cells are treated with DNA replication stress conditions. We conducted a quantitative proteomic analysis in a U2OS cell line stably expressing SUMO2(Q87R) tagged with StrepHA in the presence or absence of epoxomicin (EPOX), a proteasome inhibitor. We identified subgroups of putative SUMO2 targets that were either degraded or stabilized by EPOX upon SUMO2 conjugation in response to replication stress. Interestingly, the subgroup of proteins degraded upon SUMO2 conjugation was enriched in proteins playing roles in DNA damage repair and replication, while the proteins stabilized upon SUMOylation were mainly involved in chromatin maintenance. In addition, we identified 43 SUMOylation sites in target proteins, of which 17 are located in the proximity of phosphorylated residues. Considering that DNA replication stress is a major source of genome instability, which is suggested to drive tumorigenesis and possibly aging, our data will facilitate future functional studies in the fields of DNA metabolism and cancer biology.

Original publication

DOI

10.1021/pr500997p

Type

Journal article

Journal

J Proteome Res

Publication Date

03/04/2015

Volume

14

Pages

1687 - 1699

Keywords

DNA replication stress, SUMOylation consensus sites, epoxomicin, mass spectrometry, proteolysis, Blotting, Western, Cell Cycle Proteins, Cell Physiological Phenomena, Cloning, Molecular, DNA Replication, Flow Cytometry, Humans, Mass Spectrometry, Microscopy, Fluorescence, Oligopeptides, Proteasome Endopeptidase Complex, Proteolysis, Proteomics, Small Ubiquitin-Related Modifier Proteins, Stress, Physiological