O-GlcNAc modification of Sp3 and Sp4 transcription factors negatively regulates their transcriptional activities

Biochem Biophys Res Commun. 2015 Nov 13;467(2):341-7. doi: 10.1016/j.bbrc.2015.09.155. Epub 2015 Oct 6.


The addition of O-linked N-acetylglucosamine (O-GlcNAc) on serine or threonine modifies a myriad of proteins and regulates their function, stability and localization. O-GlcNAc modification is common among chromosome-associated proteins, such as transcription factors, suggesting its extensive involvement in gene expression regulation. In this study, we demonstrate the O-GlcNAc status of the Sp family members of transcription factors and the functional impact on their transcriptional activities. We highlight the presence of O-GlcNAc residues in Sp3 and Sp4, but not Sp2, as demonstrated by their enrichment in GlcNAc positive protein fractions and by detection of O-GlcNAc residues on Sp3 and Sp4 co-expressed in Escherichia coli together with O-GlcNAc transferase (OGT) using an O-GlcNAc-specific antibody. Deletion mutants of Sp3 and Sp4 indicate that the majority of O-GlcNAc sites reside in their N-terminal transactivation domain. Overall, using reporter gene assays and co-immunoprecipitations, we demonstrate a functional inhibitory role of O-GlcNAc modifications in Sp3 and Sp4 transcription factors. Thereby, our study strengthens the current notion that O-GlcNAc modification is an important regulator of protein interactome.

Keywords: Interaction; O-GlcNAc; Sp3; Sp4; Transcription.

MeSH terms

  • Acetylglucosamine / metabolism*
  • Escherichia coli
  • Genes, Reporter
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Luciferases / genetics
  • Luciferases / metabolism
  • N-Acetylglucosaminyltransferases / genetics
  • N-Acetylglucosaminyltransferases / metabolism
  • Plasmids / chemistry
  • Plasmids / metabolism
  • Protein Processing, Post-Translational*
  • Protein Structure, Tertiary
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Serine / metabolism
  • Signal Transduction
  • Sp2 Transcription Factor / genetics
  • Sp2 Transcription Factor / metabolism
  • Sp3 Transcription Factor / genetics
  • Sp3 Transcription Factor / metabolism*
  • Sp4 Transcription Factor / genetics
  • Sp4 Transcription Factor / metabolism*
  • Threonine / metabolism
  • Transcription, Genetic*


  • Recombinant Proteins
  • SP2 protein, human
  • SP3 protein, human
  • SP4 protein, human
  • Sp4 Transcription Factor
  • Sp2 Transcription Factor
  • Sp3 Transcription Factor
  • Threonine
  • Serine
  • Luciferases
  • N-Acetylglucosaminyltransferases
  • O-GlcNAc transferase
  • Acetylglucosamine