Human Regulatory Protein Ki-1/57 Is a Target of SUMOylation and Affects PML Nuclear Body Formation

J Proteome Res. 2017 Sep 1;16(9):3147-3157. doi: 10.1021/acs.jproteome.7b00001. Epub 2017 Jul 31.


Ki-1/57 is a nuclear and cytoplasmic regulatory protein first identified in malignant cells from Hodgkin's lymphoma. It is involved in gene expression regulation on both transcriptional and mRNA metabolism levels. Ki-1/57 belongs to the family of intrinsically unstructured proteins and undergoes phosphorylation by PKC and methylation by PRMT1. Previous characterization of its protein interaction profile by yeast two-hybrid screening showed that Ki-1/57 interacts with proteins of the SUMOylation machinery, the SUMO E2 conjugating enzyme UBC9 and the SUMO E3 ligase PIAS3, which suggested that Ki-1/57 could be involved with this process. Here we identified seven potential SUMO target sites (lysine residues) on Ki-1/57 sequence and observed that Ki-1/57 is modified by SUMO proteins in vitro and in vivo. We showed that SUMOylation of Ki-1/57 occurred on lysines 213, 276, and 336. In transfected cells expressing FLAG-Ki-1/57 wild-type, its paralog FLAG-CGI-55 wild-type, or their non-SUMOylated triple mutants, the number of PML-nuclear bodies (PML-NBs) is reduced compared with the control cells not expressing the constructs. More interestingly, after treating cells with arsenic trioxide (As2O3), the number of PML-NBs is no longer reduced when the non-SUMOylated triple mutant Ki-1/57 is expressed, suggesting that the SUMOylation of Ki-1/57 has a role in the control of As2O3-induced PML-NB formation. A proteome-wide analysis of Ki-1/57 partners in the presence of either SUMO-1 or SUMO-2 suggests that the involvement of Ki-1/57 with the regulation of gene expression is independent of the presence of either SUMO-1 or SUMO-2; however, the presence of SUMO-1 strongly influences the interaction of Ki-1/57 with proteins associated with cellular metabolism, maintenance, and cell cycle.

Keywords: CGI-55; Ki-1/57; PML-NBs; SUMOylation; arsenic trioxide; posttranslational modifications.

MeSH terms

  • Arsenic Trioxide
  • Arsenicals / pharmacology
  • Cell Cycle / genetics
  • Cell Nucleus / drug effects
  • Cell Nucleus / genetics
  • Cell Nucleus / metabolism
  • Cloning, Molecular
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Lysine
  • Myogenic Regulatory Factors / genetics
  • Myogenic Regulatory Factors / metabolism*
  • Oligopeptides / genetics
  • Oligopeptides / metabolism
  • Oxides / pharmacology
  • Plasmids / chemistry
  • Plasmids / metabolism
  • Protein Binding
  • Protein Biosynthesis
  • Protein Interaction Mapping*
  • Protein Processing, Post-Translational*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • SUMO-1 Protein / genetics
  • SUMO-1 Protein / metabolism*
  • Small Ubiquitin-Related Modifier Proteins / genetics
  • Small Ubiquitin-Related Modifier Proteins / metabolism*
  • Sumoylation
  • Transcription, Genetic


  • Arsenicals
  • HABP4 protein, human
  • Myogenic Regulatory Factors
  • Oligopeptides
  • Oxides
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins
  • SERBP1 protein, human
  • SUMO-1 Protein
  • SUMO1 protein, human
  • SUMO2 protein, human
  • Small Ubiquitin-Related Modifier Proteins
  • FLAG peptide
  • Lysine
  • Arsenic Trioxide