title: Negative modulation of RXRalpha transcriptional activity by small ubiquitin-related modifier (SUMO) modification and its reversal by SUMO-specific protease SUSP1.
abstract: Retinoid X receptor alpha (RXRalpha) belongs to a family of ligand-activated transcription factors that regulate many aspects of metazoan life. Here we demonstrate that RXRalpha is a target substrate of a small ubiquitin-related modifier (SUMO)-specific protease, SUSP1, which is capable of controlling the transcriptional activity of RXRalpha. RXRalpha was modified by SUMO-1 in vivo as well as in vitro, and the Lys-108 residue within the IKPP sequence of RXRalpha AF-1 domain was identified as the major SUMO-1 acceptor site. Prevention of SUMO modification by Lys-to-Arg mutation led to an increase not only in the transcriptional activity of RXRalpha but also in the activity of its heterodimeric complex with retinoic acid receptor-alpha or peroxisome proliferator-activated receptor-gamma (PPARgamma). SUSP1 co-localized with RXRalpha in the nucleus and removed SUMO-1 from RXRalpha but not from androgen receptor or PPARgamma. Moreover, overexpression of SUSP1 caused an increase in the transcriptional activity of RXRalpha, whereas small hairpin RNA-mediated knockdown of endogenous SUSP1 led to a decrease in RXRalpha activity. These results suggest that SUSP1 plays an important role in the control of the transcriptional activity of RXRalpha and thus in the RXRalpha-mediated cellular processes.
authors.affiliation: National Research Laboratory of Protein Biochemistry, School of Biological Sciences, Seoul National University, Seoul 151-742, Korea.
authors.forename: Soo Joon
authors.initials: SJ
authors.lastname: Choi
authors.forename: Sung Soo
authors.initials: SS
authors.lastname: Chung
authors.forename: Eun Jung
authors.initials: EJ
authors.lastname: Rho
authors.forename: Hyung Woo
authors.initials: HW
authors.lastname: Lee
authors.forename: Moon Hee
authors.initials: MH
authors.lastname: Lee
authors.forename: Hueng-Sik
authors.initials: HS
authors.lastname: Choi
authors.forename: Jae Hong
authors.initials: JH
authors.lastname: Seol
authors.forename: Sung Hee
authors.initials: SH
authors.lastname: Baek
authors.forename: Ok Sun
authors.initials: OS
authors.lastname: Bang
authors.forename: Chin Ha
authors.initials: CH
authors.lastname: Chung
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008239:Lysine / Q000737:chemistry; D047495:PPAR gamma / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D047490:Retinoid X Receptor alpha / Q000096:biosynthesis* / Q000235:genetics*; D025842:SUMO-1 Protein / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D047495:PPAR gamma; D012333:RNA, Messenger; D047490:Retinoid X Receptor alpha; D025842:SUMO-1 Protein; D005982:Glutathione Transferase; D003546:Cysteine Endopeptidases; C408873:SENP6 protein, human; D008239:Lysine