Ribosomal Protein S3 Negatively Regulates Unwinding Activity of RecQ-like Helicase 4 through Their Physical...

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Protein-Protein Interactions

Background:

• Human RecQ-like helicase 4 (RECQL4) is vital for DNA replication and repair, but its activity regulation is unclear.
• RECQL4 mutations cause diseases like Rothmund-Thomson syndrome, highlighting its importance.
• Ribosomal protein S3 (RPS3) has DNA repair functions and shares some phenotypic similarities with RECQL4 mutations.

Purpose of the Study:

• To investigate the functional and physical interaction between RECQL4 and RPS3.
• To understand how RPS3 regulates RECQL4's biochemical activities.
• To determine the role of this interaction in cellular stress responses.

Main Methods:

• Co-immunoprecipitation to confirm physical interaction.
• In vitro assays to assess ATPase, DNA binding, and helicase activities.
• Domain mapping to identify interacting regions of RECQL4 and RPS3.
• Cellular stress experiments (oxidative stress, UV exposure) in U2OS cells.

Main Results:

• A functional and physical interaction between RECQL4 and RPS3 was confirmed.
• RPS3 directly inhibits RECQL4's ATPase, DNA binding, and helicase activities.
• The N-terminus of RECQL4 (1-320 aa) interacts with the C-terminus of RPS3 (94-244 aa).
• The C-terminal domain of RPS3 possesses endonuclease-like activity.
• Interaction between nuclear RPS3 and RECQL4 is enhanced by oxidative stress and UV exposure.

Conclusions:

• RPS3 directly regulates RECQL4's enzymatic activities through physical interaction.
• The interaction is enhanced under cellular stress, suggesting a role in DNA repair modulation.
• This regulatory mechanism may be crucial for maintaining genomic stability.