Reading SUMO Chains: SUMO binding properties of Daxx.

Tuesday, October 09, 2012 — Poster Session I
1:00 p.m. – 3:00 p.m	Natcher Conference Center, Building 45	NICHD	BIOCHEM-10

Authors

• M Lyanguzova
• I Gorshkova
• A Arnaoutov
• M Dasso

Abstract

Small Ubiquitin-like modifiers (SUMOs) are family of proteins that can be covalentely conjugated to target proteins as single moieties, or as chains of several SUMOs. There is a growing evidence that SUMO monomers and chains confer alternative fates to their targets, through monomer- or chain-specific interactions. We are interested in SUMO chain-interacting proteins, which essentially read poly-SUMO signals. Daxx is a novel histone chaperone that interacts with many nuclear binding partners. Daxx contains two SUMO-interacting motifs (SIMs), located at its N- and C- termini. Both SIM domains interact with SUMO monomers, but Daxx’s relative affinity for chain binding has not been investigated. We examined Daxx’s interaction with SUMO chains of different lengths, and found that Daxx has a much higher affinity for SUMO chains that contain at least three SUMO moieties than it does for monomers or dimeric chain. We demonstrated that only C-terminal SIM is required for correct sub-nuclear localization of Daxx in SUMO-rich foci. We also found that Daxx behaves as an oligomer, both as recombinant protein and within cell extracts. Our findings indicate that Daxx preferentially binds long SUMO chains. We are currently investigating how Daxx’s oligomeric status may contribute to this interaction.

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