RNF219 RING Finger Domain Mutants Drive Phase Separation to Encapsulate CCR4-NOT and Promote Cell Proliferation

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• RING finger protein 219 (RNF219) functions as a co-factor for the CCR4-NOT deadenylase complex in mammals.
• The CCR4-NOT complex is crucial for regulating mRNA stability and gene expression through deadenylation.

Purpose of the Study:

• To investigate the role of RNF219 mutations in condensate formation and their impact on CCR4-NOT complex activity.
• To elucidate the pathogenic mechanism linking RNF219 mutations to altered cellular processes.

Main Methods:

• Analysis of RNF219 mutations within the RING finger domain and their effect on liquid-liquid phase separation (LLPS).
• Assessment of the role of the coiled-coil 1 (CC1) domain in RNF219 condensate formation.
• Investigation of the interaction between mutant RNF219 condensates and the CCR4-NOT complex.
• Evaluation of the impact of RNF219 mutations on RNA deadenylation activity and cell proliferation.

Main Results:

• Mutations in the RNF219 RING finger domain enable condensate formation via LLPS, which is promoted by the adjacent CC1 domain.
• Wild-type RNF219 intrinsically suppresses LLPS.
• Mutant RNF219 condensates encapsulate the CCR4-NOT complex, inhibiting its deadenylation activity.
• RNF219 mutations were observed to promote cell proliferation.

Conclusions:

• RNF219 mutations can induce the formation of CCR4-NOT condensates through LLPS.
• Inhibition of deadenylation-dependent mRNA decay by RNF219 mutations contributes to increased cell proliferation.
• These findings reveal a novel pathogenic mechanism involving RNF219 mutations, condensate formation, and cellular dysregulation.