title: The polycomb repressive complex 2 is a potential target of SUMO modifications.
abstract: BACKGROUND
  The Polycomb Repressive Complex 2 (PRC2) functions as a transcriptional repressor through a mechanism that involves methylation of Histone H3 at lysine 27. The PRC2 complex activity is essential for cellular proliferation, development, and cell fate decisions. PRC2 target genes include important regulators of development and proliferation as well as tumor suppressor genes. Consistent with this, the activity of several Polycomb group (PcG) proteins is deregulated in human cancer suggesting an important role for PcGs in tumor development. Whereas the downstream functions of PcGs are well characterized, the mechanisms of their recruitment to target genes and the regulation of their activity are not fully understood.
  
  
  RESULTS
  Here we show that the two PRC2 components SUZ12 and EZH2 are sumoylated in vitro and in vivo. Among several putative sumoylation sites we have mapped the major site of SUZ12 sumoylation. Furthermore, we show that SUZ12 interacts with the E2-conjugating enzyme UBC9 both in vitro and in vivo and that mutation of the SUZ12 sumoylation site does not abolish this binding. Finally, we provide evidence that the E3-ligase PIASXbeta interacts and enhances the sumoylation of SUZ12 in vivo suggesting that PIASXbeta could function as an E3-ligase for SUZ12.
  
  
  CONCLUSIONS
  Taken together, our data identify sumoylation as a novel post-translational modification of components of the PRC2 complex, which could suggest a potential new mechanism to modulate PRC2 repressive activity. Further work aimed to identify the physiological conditions for these modifications will be required to understand the role of SUZ12 and EZH2 sumoylation in PcG-mediated epigenetic regulation of transcription.
authors.affiliation: Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Eva Madi
authors.initials: EM
authors.lastname: Riising
authors.forename: Roberto
authors.initials: R
authors.lastname: Boggio
authors.forename: Susanna
authors.initials: S
authors.lastname: Chiocca
authors.forename: Kristian
authors.initials: K
authors.lastname: Helin
authors.forename: Diego
authors.initials: D
authors.lastname: Pasini
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D009687:Nuclear Proteins / Q000378:metabolism; D063151:Polycomb Repressive Complex 2; D063146:Polycomb-Group Proteins; D050828:Protein Inhibitors of Activated STAT / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000737:chemistry; D012097:Repressor Proteins / Q000378:metabolism*; D025842:SUMO-1 Protein / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C501001:PIAS2 protein, human; D063146:Polycomb-Group Proteins; D050828:Protein Inhibitors of Activated STAT; D011994:Recombinant Proteins; D012097:Repressor Proteins; D025842:SUMO-1 Protein; C495501:SUMO1 protein, human; C430461:SUZ12 protein, human; D014157:Transcription Factors; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2