A novel factor required for the SUMO1/Smt3 conjugation of yeast septins.

SUMO1/Smt3, a ubiquitin-like protein modifier, is known to be conjugated to other proteins and modulate their functions in various important processes. Similar to the ubiquitin system, SUMO1/Smt3 is activated in an ATP-dependent reaction by thioester bond formation with E1 (activating enzyme), transferred to E2 (conjugating enzyme), and passed to a ...
substrate lysine. It remained unknown, however, whether any SUMO1/Smt3 ligases (E3s) are involved in the final transfer of this modifier. Here we report a novel factor Siz1 (YDR409w) required for septin-sumoylation of budding yeast, possibly acting as E3. Siz1 is a member of a new family (Miz1, PIAS3, etc.) containing a conserved domain with a similarity to a zinc-binding RING-domain, often found in ubiquitin ligases. In the siz1 mutant septin-sumoylation was completely abolished. A conserved cysteine residue in the domain was essential for this conjugation. Furthermore, Siz1 was localized at the mother-bud neck in the M-phase and physically bound to both E2 and the target proteins.
Mesh Terms:
Amino Acid Sequence, Cell Cycle Proteins, Electrophoretic Mobility Shift Assay, Fluorescent Antibody Technique, Indirect, Fungal Proteins, Green Fluorescent Proteins, Indoles, Ligases, Luminescent Proteins, Microscopy, Fluorescence, Mitosis, Molecular Sequence Data, Phosphorylation, Profilins, Protein Binding, Recombinant Fusion Proteins, SUMO-1 Protein, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Homology, Amino Acid, Two-Hybrid System Techniques, Ubiquitin-Conjugating Enzymes, Zinc Fingers
Gene
Date: Sep. 19, 2001
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