title: The transcriptional activity of co-activator AIB1 is regulated by the SUMO E3 ligase PIAS1.
abstract: BACKGROUND
  Amplified in breast cancer 1 (AIB1) is a transcriptional coactivator of nuclear receptors and other transcription factors. It is required for animal growth and reproductive development, and has also been implicated in breast carcinogenesis. Although AIB1 is known to be covalently modified by SUMO-1, which serves to regulate its stability and transcriptional activity, the exact SUMO E3 ligase involved in its sumoylation has not been determined. In order to resolve this question, we investigated the interaction between AIB1 and different members of PIAS proteins (all are SUMO E3 ligases) through immunoprecipiation.
  
  
  RESULTS
  Among the five different PIAS proteins, only PIAS1 co-immunoprecipitated with AIB1 in extract prepared from breast cancer cells (MCF-7). Over-expression of PIAS1 together with AIB1 in MCF-7 cells led to increased sumoylation of AIB1, resulting in repression of its transcriptional activity. In contrast, the PIAS1 mutant (C350S) lacking E3 ligase activity appeared to have no effect on the sumoylation of AIB1. Through sumoylation of AIB1, PIAS1 also promoted the stability of AIB1 and attenuated its interaction with estrogen receptor α (ERα), resulting in repression of the transactivation activity of ERα. In addition, MCF-7 cells co-transfected with wild-type PIAS1 and AIB1 showed about 40% reduction in cell growth, while cells co-transfected with wild-type PIAS1 and mutant AIB1 resistant to sumoylation showed about 34% increase in cell growth compared to cells transformed with wild-type AIB1 only.
  
  
  CONCLUSIONS
  Taken together, these results suggested that PIAS1 may play a crucial role in the regulation of AIB1 transcriptional activity through sumoylation.
authors.affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Shujing
authors.initials: S
authors.lastname: Li
authors.forename: Chunhua
authors.initials: C
authors.lastname: Yang
authors.forename: Yongde
authors.initials: Y
authors.lastname: Hong
authors.forename: Hailian
authors.initials: H
authors.lastname: Bi
authors.forename: Feng
authors.initials: F
authors.lastname: Zhao
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiang
authors.initials: X
authors.lastname: Ao
authors.forename: Pengsha
authors.initials: P
authors.lastname: Pang
authors.forename: Xinrong
authors.initials: X
authors.lastname: Xing
authors.forename: Alan K
authors.initials: AK
authors.lastname: Chang
authors.forename: Liyun
authors.initials: L
authors.lastname: Xiao
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Huijian
authors.initials: H
authors.lastname: Wu
mesh_terms: D045744:Cell Line, Tumor; D006801:Humans; D056921:Nuclear Receptor Coactivator 3 / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D050828:Protein Inhibitors of Activated STAT / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism*; D058207:Sumoylation; D015533:Transcriptional Activation; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: C106529:PIAS1 protein, human; D050828:Protein Inhibitors of Activated STAT; D025841:Small Ubiquitin-Related Modifier Proteins; C538866:NCOA3 protein, human; D056921:Nuclear Receptor Coactivator 3; D044767:Ubiquitin-Protein Ligases