Proteasomal degradation of the KLF5 transcription factor through a ubiquitin-independent pathway.
KLF5 is a Kruppel-like zinc finger transcription factor modulating cell proliferation, differentiation, cell cycle, apoptosis, and angiogenesis. The KLF5 protein undergoes multiple posttranslational modifications including phosphorylation, acetylation and ubiquitination. We have demonstrated that the KLF5 protein can be ubiquitinated by the WWP1 E3 ubiquitin ligase and degraded by the proteasome. In this study, we found that KLF5 protein degradation is blocked by an N-terminal FLAG tag or a small N-terminal deletion without reducing ubiquitination and degradation mediated by WWP1. Interestingly, the N-terminal fragments of KLF5 containing the first 237 or 171 amino acids are as unstable as the full length KLF5 protein. The N-terminal FLAG tag or 19 amino acid deletion also delayed the degradation of the C-terminal truncated KLF5 proteins. To further understand the mechanism, we generated a lysine-less mutant KLF5(1-171). This mutant is efficiently degraded by the proteasome without ubiquitination in vitro and in vivo. These findings suggest that KLF5 protein degradation by the proteasome could be regulated in a ubiquitin-independent manner.
Chen
Ceshi
C
The Center for Cell Biology and Cancer Research, MS355, Albany Medical College, 47 New Scotland Avenue, Albany, NY 12208, USA. chenc@mail.amc.edu
Zhou
Zhongmei
Z
Guo
Peng
P
Dong
Jin-Tang
JT
D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009842:Oligopeptides; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010455:Peptides; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
C492214:KLF5 protein, human; D051741:Kruppel-Like Transcription Factors; D009842:Oligopeptides; D010446:Peptide Fragments; D010455:Peptides; D025801:Ubiquitin; C085706:FLAG peptide; C471642:WWP1 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex