RNF20-RNF40: A ubiquitin-driven link between gene expression and the DNA damage response

Area of Science:

• Cellular Biology
• Molecular Biology
• Genetics

Background:

• The DNA damage response (DDR) is a complex network that manages cellular metabolism during DNA damage, particularly double-strand breaks (DSBs).
• Key DDR players include ATM protein kinase and dynamic post-translational modifications like phosphorylation and ubiquitylation.
• Histone H2B monoubiquitylation (H2Bub) is a novel DDR component, primarily regulated by the RNF20/RNF40 E3 ubiquitin ligase in mammalian cells.

Purpose of the Study:

• To elucidate the role of histone H2B monoubiquitylation in the DNA damage response.
• To investigate how H2Bub influences gene expression and chromatin organization during DNA repair.
• To understand the connection between H2Bub, RNF20/RNF40, and genome stability.

Main Methods:

• Investigated the recruitment of the H2Bub module to DSB sites.
• Analyzed the impact of H2Bub on gene expression using the hPAF1 complex and TFIIS protein.
• Assessed the role of RNF20 and RNF40 in regulating H2Bub and its downstream effects.

Main Results:

• H2Bub is recruited to DSB sites, promoting local H2Bub accumulation.
• Local H2Bub is essential for the timely recruitment of DSB repair proteins.
• H2Bub selectively enhances or suppresses gene expression, impacting cell growth and genome stability genes.
• RNF20 and RNF40 function as tumor suppressors through their regulation of H2Bub.

Conclusions:

• The H2B monoubiquitylation pathway is a critical link between the DDR and chromatin organization.
• The DDR hijacks regulatory modules like H2Bub, normally involved in other cellular processes, to facilitate DNA repair.
• RNF20/RNF40-mediated H2Bub plays a significant role in maintaining genome stability and preventing tumorigenesis.