Article

Structure of the Small Ubiquitin-like Modifier (SUMO)-interacting Motif of MBD1-containing Chromatin-associated Factor 1 Bound to SUMO-3

Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2008; 283(51):35966-75. DOI: 10.1074/jbc.M802528200
Source: PubMed

ABSTRACT Post-translational modification by small ubiquitin-like modifier (SUMO) proteins has been implicated in the regulation of
a variety of cellular events. The functions of sumoylation are often mediated by downstream effector proteins harboring SUMO-interacting
motifs (SIMs) that are composed of a hydrophobic core and a stretch of acidic residues. MBD1-containing chromatin-associated
factor 1 (MCAF1), a transcription repressor, interacts with SUMO-2/3 and SUMO-1, with a preference for SUMO-2/3. We used NMR
spectroscopy to solve the solution structure of the SIM of MCAF1 bound to SUMO-3. The hydrophobic core of the SIM forms a
parallel β-sheet pairing with strand β2 of SUMO-3, whereas its C-terminal acidic stretch seems to mediate electrostatic interactions
with a surface area formed by basic residues of SUMO-3. The significance of these electrostatic interactions was shown by
mutations of both SUMO-3 and MCAF1. The present structural and biochemical data suggest that the acidic stretch of the SIM
of MCAF1 plays an important role in the binding to SUMO-3.

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    • "K33 is one of the critical amino acids for the transcriptional inhibitory properties of SUMO2 and is likely involved in the binding to SIM-containing corepressors (Chupreta et al., 2005; Rosendorff et al., 2006). Structural data indeed demonstrate that K33 of SUMO2 forms a salt bridge with an aspartic acid in the SIM of the corepressor MCAF1 (Sekiyama et al., 2008). Consistent with these findings, the acetyl-mimicking SUMO2 K33Q variant exhibits a strongly reduced repressive potential, indicating that SUMO-dependent gene repression is directly regulated by acetylation. "
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    • "This alignment revealed conserved residues, found in overlapping secondary structures, suitable as potential target sites for mutagenesis. We next generated a point mutation of a conserved lysine residue (K595E) in SLD2 (indicated with an asterisk in Fig. 6C), as the corresponding lysine on SUMO2 (K33) was critical in SUMO–SIM interaction (Sekiyama et al. 2008). Compared with the wild-type Flag-UAF1 protein, the K595E mutant exhibited a much weaker interaction with the SIM sequence of hELG1, although the same mutant protein bound normally to USP1 (Fig. 6D). "
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    • ") . Val 30 , Phe 32 , Ile 34 , Thr 38 , and Leu 43 on SUMO3 have been shown to contact a canonical SIM in MCAF1 ( the MBD1 ½methyl - CpG - binding domain protein 1Š - containing chromatin - associated factor 1 ) ( Sekiyama et al . 2008 ) . A similar surface in SUMO1 or SUMO2 / 3 has also been shown to be involved in binding to the hydrophobic SIM region of PIAS family members ( Hecker et al . 2006 ) . Remarkably , positively charged residues in SUMO paralogs , including Lys 33 of SUMO2 , which is conserved in the SLD2 of UAF1 , contribute to SIM binding . Note that op"
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