title: PIAS1 binds p300 and behaves as a coactivator or corepressor of the transcription factor c-Myb dependent on SUMO-status.
abstract: The PIAS proteins (Protein Inhibitor of Activated STATs) constitute a family of multifunctional nuclear proteins operating as SUMO E3 ligases and being involved in a multitude of interactions. They participate in a range of biological processes, also beyond their well-established role in the immune system and cytokine signalling. They act both as transcriptional corepressors and coactivators depending on the context. In the present work, we investigated mechanisms by which PIAS1 causes activation or repression of c-Myb dependent target genes. Analysis of global expression data shows that c-Myb and PIAS1 knockdowns affect a subset of common targets, but with a dual outcome consistent with a role of PIAS1 as either a corepressor or coactivator. Our mechanistic studies show that PIAS1 engages in a novel interaction with the acetyltransferase and coactivator p300. Interaction and ChIP analysis suggest a bridging function where PIAS1 enhances p300 recruitment to c-Myb-bound sites through interaction with both proteins. In addition, the E3 activity of PIAS1 enhances further its coactivation. Remarkably, the SUMO status of c-Myb had a decisive role, indicating a SUMO-dependent switch in the way PIAS1 affects c-Myb, either as a coactivator or corepressor. Removal of the two major SUMO-conjugation sites in c-Myb (2KR mutant), which enhances its activity significantly, turned PIAS1 into a corepressor. Also, p300 was less efficiently recruited to chromatin by c-Myb-2KR. We propose that PIAS1 acts as a "protein inhibitor of activated c-Myb" in the absence of SUMOylation while, in its presence, PIAS behaves as a "protein activator of repressed c-Myb".
authors.affiliation: Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. Electronic address: marit.ledsaak@ibv.uio.no.
authors.forename: Marit
authors.initials: M
authors.lastname: Ledsaak
authors.affiliation: Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. Electronic address: mads.bengtsen@ibv.uio.no.
authors.forename: Mads
authors.initials: M
authors.lastname: Bengtsen
authors.affiliation: Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. Electronic address: a.k.molvarsmyr@odont.uio.no.
authors.forename: Ann-Kristin
authors.initials: AK
authors.lastname: Molværsmyr
authors.affiliation: Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. Electronic address: b.m.fuglerud@ibv.uio.no.
authors.forename: Bettina Maria
authors.initials: BM
authors.lastname: Fuglerud
authors.affiliation: Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. Electronic address: vilborg.matre@ibv.uio.no.
authors.forename: Vilborg
authors.initials: V
authors.lastname: Matre
authors.affiliation: Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. Electronic address: ragnhild.eskeland@ibv.uio.no.
authors.forename: Ragnhild
authors.initials: R
authors.lastname: Eskeland
authors.affiliation: Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. Electronic address: o.s.gabrielsen@ibv.uio.no.
authors.forename: Odd Stokke
authors.initials: OS
authors.lastname: Gabrielsen
mesh_terms: D002843:Chromatin / Q000235:genetics; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D011485:Protein Binding / Q000235:genetics; D050828:Protein Inhibitors of Activated STAT / Q000235:genetics* / Q000378:metabolism; D020598:Proto-Oncogene Proteins c-myb / Q000096:biosynthesis / Q000235:genetics*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics* / Q000378:metabolism; D058207:Sumoylation / Q000235:genetics; D050880:p300-CBP Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D002843:Chromatin; C106529:PIAS1 protein, human; D050828:Protein Inhibitors of Activated STAT; D020598:Proto-Oncogene Proteins c-myb; D025841:Small Ubiquitin-Related Modifier Proteins; D050880:p300-CBP Transcription Factors
keywords: Coactivator; PIAS1; SUMOylation; Transcription factor; c-Myb; p300