title: Hes-1 SUMOylation by protein inhibitor of activated STAT1 enhances the suppressing effect of Hes-1 on GADD45α expression to increase cell survival.
abstract: BACKGROUND
  Hairy and Enhancer of split 1 (Hes-1) is a transcriptional repressor that plays an important role in neuronal differentiation and development, but post-translational modifications of Hes-1 are much less known. In the present study, we aimed to investigate whether Hes-1 could be SUMO-modified and identify the candidate SUMO acceptors on Hes-1. We also wished to examine the role of the SUMO E3 ligase protein inhibitor of activated STAT1 (PIAS1) in SUMOylation of Hes-1 and the molecular mechanism of Hes-1 SUMOylation. Further, we aimed to identify the molecular target of Hes-1 and examine how Hes-1 SUMOylation affects its molecular target to affect cell survival.
  
  
  RESULTS
  In this study, by using HEK293T cells, we have found that Hes-1 could be SUMO-modified and Hes-1 SUMOylation was greatly enhanced by the SUMO E3 ligase PIAS1 at Lys8, Lys27 and Lys39. Furthermore, Hes-1 SUMOylation stabilized the Hes-1 protein and increased the transcriptional suppressing activity of Hes-1 on growth arrest and DNA damage-inducible protein alpha (GADD45α) expression. Overexpression of GADD45α increased, whereas knockdown of GADD45αα expression decreased cell apoptosis. In addition, H2O2 treatment increased the association between PIAS1 and Hes-1 and enhanced the SUMOylation of Hes-1 for endogenous protection. Overexpression of Hes-1 decreased H2O2-induced cell death, but this effect was blocked by transfection of the Hes-1 triple sumo-mutant (Hes-1 3KR). Overexpression of PIAS1 further facilitated the anti-apoptotic effect of Hes-1. Moreover, Hes-1 SUMOylation was independent of Hes-1 phosphorylation and vice versa.
  
  
  CONCLUSIONS
  The present results revealed, for the first time, that Hes-1 could be SUMO-modified by PIAS1 and GADD45α is a novel target of Hes-1. Further, Hes-1 SUMOylation mediates cell survival through enhanced suppression of GADD45α expression. These results revealed a novel role of Hes-1 in addition to its involvement in Notch signaling. They also implicate that SUMOylation could be an important posttranslational modification that regulates cell survival.
authors.forename: Hsin-Ying Clair
authors.initials: HY
authors.lastname: Chiou
authors.forename: Shau-Yu
authors.initials: SY
authors.lastname: Liu
authors.forename: Cheng-Hsiung
authors.initials: CH
authors.lastname: Lin
authors.affiliation: Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan. eminy@gate.sinica.edu.tw.
authors.forename: Eminy Hy
authors.initials: EH
authors.lastname: Lee
mesh_terms: D017209:Apoptosis / Q000235:genetics; D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000378:metabolism; D002470:Cell Survival / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000378:metabolism; D010766:Phosphorylation; D050794:STAT1 Transcription Factor / Q000096:biosynthesis* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D058207:Sumoylation / Q000235:genetics*; D000072056:Transcription Factor HES-1; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D000097642:GADD45 Proteins
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D018398:Homeodomain Proteins; D006861:Hydrogen Peroxide; D009687:Nuclear Proteins; D050794:STAT1 Transcription Factor; D000072056:Transcription Factor HES-1; D044767:Ubiquitin-Protein Ligases; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C494079:STAT1 protein, human; C078493:HES1 protein, human