A UAF1-containing multisubunit protein complex regulates the Fanconi anemia pathway

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• The deubiquitinating enzyme USP1 regulates Ub-FANCD2 levels, a critical protein in the Fanconi anemia DNA repair pathway.
• Understanding USP1 regulation is vital for comprehending DNA damage response mechanisms.

Purpose of the Study:

• To investigate the regulatory mechanisms of USP1 activity.
• To identify and characterize proteins that interact with USP1.
• To elucidate the role of USP1 in DNA repair.

Main Methods:

• Purification of the USP1 multisubunit protein complex from HeLa cells.
• In vitro reconstitution assays using Ub-AMC and monoubiquitinated FANCD2.
• Analysis of USP1 gene transcription following DNA damage.

Main Results:

• A USP1-associated factor 1 (UAF1) protein was identified as a stoichiometric component of the USP1 complex.
• UAF1 acts as an activator of USP1 deubiquitinating activity, increasing catalytic turnover but not substrate affinity.
• DNA damage triggers rapid transcriptional shutoff of the USP1 gene, reducing USP1/UAF1 complex levels.

Conclusions:

• UAF1 is a critical activator of USP1, enhancing its catalytic efficiency.
• The cellular levels of the USP1/UAF1 complex are dynamically regulated by DNA damage through transcriptional control.
• These findings reveal a novel regulatory mechanism for USP1 and its role in DNA repair.