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Transcription factor Sp3 is silenced through SUMO modification by PIAS1
Alexandra Sapetschnig1, Grigore Rischitor, Harald Braun
1Institut für Molekularbiologie und Tumorforschung, Emil-Mannkopff-Strasse 2, D-35037 Marburg, Germany.
The EMBO Journal
|October 3, 2002
Summary
The transcription factor Sp3 is regulated by SUMO modification, which silences its activity. Protein inhibitor of activated STAT1 (PIAS1) acts as an E3 ligase for this process, impacting Sp3
Area of Science:
- Molecular Biology
- Gene Regulation
- Post-translational Modifications
Background:
- Sp3 is a ubiquitous transcription factor, structurally similar to Sp1.
- Transcription factors play crucial roles in regulating gene expression.
- SUMOylation is a key post-translational modification influencing protein function.
Purpose of the Study:
- To investigate whether Sp3 is a target for SUMO modification.
- To identify the specific site and regulatory mechanism of Sp3 SUMOylation.
- To determine the functional consequence of Sp3 SUMOylation on its transcriptional activity.
Main Methods:
- In vivo and in vitro SUMOylation assays.
- Site-directed mutagenesis to identify SUMOylation sites (IKXE motif).
- Co-immunoprecipitation to identify interacting partners (PIAS1, Ubc9).
- Reporter gene assays to assess transcriptional activity.
Main Results:
- Sp3 undergoes SUMO modification at a single lysine residue.
- The IKXE motif is essential for Sp3 SUMOylation.
- PIAS1 interacts with Sp3 and Ubc9, functioning as an E3 ligase to enhance Sp3 SUMOylation.
- SUMOylation of Sp3 silences its transcriptional activity, while mutations preventing SUMOylation enhance it.
- SUMO-modified Sp3 retains DNA-binding ability, but DNA-bound Sp3 is not a substrate for further SUMOylation.
Conclusions:
- Sp3 is a novel target for SUMOylation, a process mediated by PIAS1.
- SUMOylation acts as a repressive mechanism for Sp3 transcriptional activity.
- Understanding Sp3 SUMOylation provides insights into gene regulation by transcription factors.