The ubiquitin-proteasome system is a key component of the SUMO-2/3 cycle.
Many proteins are regulated by a variety of post-translational modifications, and orchestration of these modifications is frequently required for full control of activity. Currently little is known about the combinatorial activity of different post-translational modifications. Here we show that extensive cross-talk exists between sumoylation and ubiquitination. We found that a subset of SUMO-2-conjugated proteins is subsequently ubiquitinated and degraded by the proteasome. In a screen for preferential SUMO-1 or SUMO-2 target proteins, we found that ubiquitin accumulated in purified SUMO-2 conjugates but not in SUMO-1 conjugates. Upon inhibition of the proteasome, the amount of ubiquitin in purified SUMO-2 conjugates increased. In addition, we found that endogenous SUMO-2/3 conjugates, but not endogenous SUMO-1 conjugates, accumulated in response to proteasome inhibitors. Quantitative proteomics experiments enabled the identification of 73 SUMO-2-conjugated proteins that accumulated in cells treated with proteasome inhibitors. Cross-talk between SUMO-2/3 and the ubiquitin-proteasome system controls many target proteins that regulate all aspects of nucleic acid metabolism. Surprisingly the relative abundance of 40 SUMO-2-conjugated proteins was reduced by proteasome inhibitors possibly because of a lack of recycled SUMO-2. We conclude that SUMO-2/3 conjugation and the ubiquitin-proteasome system are tightly integrated and act in a cooperative manner.
Department of Molecular Cell Biology, Leiden University Medical Center, 2300 RC Leiden, the Netherlands.
Joost
J
Schimmel
Katja M
KM
Larsen
Ivan
I
Matic
Martijn
M
van Hagen
Jürgen
J
Cox
Matthias
M
Mann
Jens S
JS
Andersen
Alfred C O
AC
Vertegaal
D000595:Amino Acid Sequence; D006367:HeLa Cells; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008954:Models, Biological; D008969:Molecular Sequence Data; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism*
D007976:Leupeptins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011994:Recombinant Proteins; D025842:SUMO-1 Protein; C495501:SUMO1 protein, human; C117909:SUMO2 protein, human; C492189:SUMO3 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins; D025801:Ubiquitin; D014452:Ubiquitins; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde