Dataset Information

The inflammatory kinase IKK? phosphorylates and stabilizes c-Myc and enhances its activity.

ABSTRACT:

Background

The I?B kinase (IKK) complex, comprising the two enzymes IKK? and IKK?, is the main activator of the inflammatory transcription factor NF-?B, which is constitutively active in many cancers. While several connections between NF-?B signaling and the oncogene c-Myc have been shown, functional links between the signaling molecules are still poorly studied.

Methods

Molecular interactions were shown by co-immunoprecipitation and FRET microscopy. Phosphorylation of c-Myc was shown by kinases assays and its activity by improved reporter gene systems. CRISPR/Cas9-mediated gene knockout and chemical inhibition were used to block IKK activity. The turnover of c-Myc variants was determined by degradation in presence of cycloheximide and by optical pulse-chase experiments.. Immunofluorescence of mouse prostate tissue and bioinformatics of human datasets were applied to correlate IKK?- and c-Myc levels. Cell proliferation was assessed by EdU incorporation and apoptosis by flow cytometry.

Results

We show that IKK? and IKK? bind to c-Myc and phosphorylate it at serines 67/71 within a sequence that is highly conserved. Knockout of IKK? decreased c-Myc-activity and increased its T58-phosphorylation, the target site for GSK3?, triggering polyubiquitination and degradation. c-Myc-mutants mimicking IKK-mediated S67/S71-phosphorylation exhibited slower turnover, higher cell proliferation and lower apoptosis, while the opposite was observed for non-phosphorylatable A67/A71-mutants. A significant positive correlation of c-Myc and IKK? levels was noticed in the prostate epithelium of mice and in a variety of human cancers.

Conclusions

Our data imply that IKK? phosphorylates c-Myc on serines-67/71, thereby stabilizing it, leading to increased transcriptional activity, higher proliferation and decreased apoptosis.

SUBMITTER: Moser B

PROVIDER: S-EPMC7812655 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Publications

The inflammatory kinase IKKα phosphorylates and stabilizes c-Myc and enhances its activity.

Moser Bernhard B Hochreiter Bernhard B Basílio José J Gleitsmann Viola V Panhuber Anja A Pardo-Garcia Alan A Hoesel Bastian B Salzmann Manuel M Resch Ulrike U Noreen Mamoona M Schmid Johannes A JA

Molecular cancer 20210118 1

<h4>Background</h4>The IκB kinase (IKK) complex, comprising the two enzymes IKKα and IKKβ, is the main activator of the inflammatory transcription factor NF-κB, which is constitutively active in many cancers. While several connections between NF-κB signaling and the oncogene c-Myc have been shown, functional links between the signaling molecules are still poorly studied.<h4>Methods</h4>Molecular interactions were shown by co-immunoprecipitation and FRET microscopy. Phosphorylation of c-Myc was s ...[more]

PMID: 33461590

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