CRY2 and FBXL3 Cooperatively Degrade c-MYC

Area of Science:

• Molecular Biology
• Chronobiology
• Cancer Research

Background:

• A link between circadian rhythms and cancer has long been suspected.
• The precise mechanisms regulating the turnover of c-MYC, a key cell proliferation factor, are not fully understood.
• The T58 phosphorylation site on c-MYC is crucial for its degradation and frequently mutated in cancers.

Purpose of the Study:

• To elucidate the role of circadian proteins in regulating c-MYC stability.
• To identify the molecular machinery responsible for c-MYC ubiquitylation and degradation.
• To clarify the distinct functions of CRY1 and CRY2 in circadian regulation.

Main Methods:

• Investigated the interaction between CRY2 and the E3 ligase FBXL3.
• Assessed the ubiquitylation and degradation of phosphorylated c-MYC.
• Utilized experiments comparing the functions of CRY1 and CRY2.

Main Results:

• CRY2 functions as a component of an FBXL3-containing E3 ligase complex.
• This complex specifically recruits and ubiquitylates T58-phosphorylated c-MYC, targeting it for degradation.
• CRY1 cannot perform this function, highlighting unique roles for CRY isoforms.

Conclusions:

• c-MYC is a direct target of CRY2-dependent protein turnover.
• This discovery provides a molecular basis for circadian control over cell growth.
• It introduces a novel paradigm for circadian regulation of protein degradation pathways relevant to cancer.