Project Details
Projekt
Mechanism and function of protein modifiaction with mixed SUMO1-Ubiquitin chains
Applicant
Professorin Dr. Frauke Melchior
Subject Area
Cell Biology
Term
from 2008 to 2015
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 72189845
Starting point of this proposal was our discovery that the small ubiquitin related modifier SUMO1 is itself subject to ubiquitylation, either in unconjugated form or when on target proteins. This suggested the existence of ubiquitin E3 ligases that can recognize and ubiquitylate SUMO1 and/or SUMO1-modified target proteins. To gain insights into mechanism and function of SUMO1-dependent ubiq-uitylation, we followed two complementary strategies: A) we enriched proteins from Hela extracts that are modified with both, endogenous SUMO1 and ubiquitin, and started to identify first target candi-dates by mass spectrometry; from this growing list we hope to now identify proteins that need SUMO1 modification for efficient ubiquitylation. These proteins will serve as model substrates for the identification of E3 ligases that recognize SUMO1 in context of a target protein. B) We searched for E3 ligases that ubiquitylate SUMO1 in vitro. This led to the identification of the F-box protein Fbxw5 as a SUMO1-interacting protein, recombinant reconstitution of SCFFbxw5, the identification of Eps8 as a first substrate for SCFFbxw5 E3, and the working hypothesis that SCFFbxw5-dependent substrates may include proteins modified with SUMO1. We will expand on this idea during the next funding period. Findings in this project will contribute to increased understanding of the interplay between sumoylation and ubiquitylation, and will provide novel insights into substrate recognition of an SCF E3 ligase.
DFG Programme
Priority Programmes
