Critical lysine residues of Klf4 required for protein stabilization and degradation

Biochem Biophys Res Commun. 2014 Jan 24;443(4):1206-10. doi: 10.1016/j.bbrc.2013.12.121. Epub 2014 Jan 2.


The transcription factor, Krüppel-like factor 4 (Klf4) plays a crucial role in generating induced pluripotent stem cells (iPSCs). As the ubiquitination and degradation of the Klf4 protein have been suggested to play an important role in its function, the identification of specific lysine sites that are responsible for protein degradation is of prime interest to improve protein stability and function. However, the molecular mechanism regulating proteasomal degradation of the Klf4 is poorly understood. In this study, both the analysis of Klf4 ubiquitination sites using several Klf4 deletion fragments and bioinformatics predictions showed that the lysine sites which are signaling for Klf4 protein degradation lie in its N-terminal domain (aa 1-296). The results also showed that Lys32, 52, 232, and 252 of Klf4 are responsible for the proteolysis of the Klf4 protein. These results suggest that Klf4 undergoes proteasomal degradation and that these lysine residues are critical for Klf4 ubiquitination.

Keywords: Oncogene; Proteasomal degradation; Tumor suppressor; Ubiquitin; Ubiquitination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • HEK293 Cells
  • Humans
  • Kruppel-Like Factor 4
  • Kruppel-Like Transcription Factors / chemistry*
  • Kruppel-Like Transcription Factors / genetics
  • Kruppel-Like Transcription Factors / metabolism*
  • Lysine / chemistry
  • Mutagenesis, Site-Directed
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Stability
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Ubiquitination


  • KLF4 protein, human
  • Kruppel-Like Factor 4
  • Kruppel-Like Transcription Factors
  • Peptide Fragments
  • Recombinant Proteins
  • Proteasome Endopeptidase Complex
  • Lysine