Protein Modification and Turnover
Miller, Marcus , Saracco, Scott , Vierstra, Richard .
Genetic Analysis of the SUMO Conjugation Machinery in Arabidopsis .
SUMOs (Small Ubiquitin like MOdifiers) are a family of ubiquitin-fold proteins in plants and animals that function by becoming covalently attached post-translationally to other intracellular proteins. Unlike, ubiquitination which targets proteins for degradation, SUMO addition confers a variety of non-proteolytic functions, including altering transcription factor activity, regulating nuclear import, and antagonizing ubiquitination. In Arabidopsis thaliana, SUMOylation has been linked genetically to phosphate deficiency, ABA signaling, and flowering time. A variety of stresses also rapidly and dramatically upregulate the abundance of SUMOylated proteins in planta, indicating that SUMO plays an important general role in stress protection. These stress-induced targets are predominantly in the nucleus but their identities are currently unknown. Here, we present a genetic dissection of SUMO conjugation in Arabidopsis that shows that SUMO addition is essential. Null mutants affecting accumulation of the E1-activating enzyme subunit SAE2 and the sole E2-conjugating enzyme SCE1 do not substantially affect male or female gametogenesis but completely arrest embryogenesis following fertilization, indicating that SUMO conjugating is required for early embryo development. Of the 8 SUMO isoforms in Arabidopsis, SUMO1 and 2 are the most closely related (91% amino acid identity) and best expressed. Genetic analysis of double null mutants showed that the expression of at least one of these isoforms is required for viability. During heat shock, both SUMO1 and SUMO2 are rapidly conjugated to other proteins in a reaction that is partially dependent on the SUMO E3 ligase SIZ1. To identify these conjugates, we have created novel SUMO variants that will facilitate the purification of SUMOylated proteins and the detection of SUMO attachment sites by mass spectrometry.
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1 - University of Wisconsin Madison, Genetics, 425 Henry Mall rm 3104, Madison, Wi, 53706, USA
2 - University of Wisconsin Madison, Genetics
Post Translational Modification.
Presentation Type: ASPB Minisymposium
Location: International Ballroom South/Hilton
Date: Wednesday, July 11th, 2007
Time: 9:45 AM