Structural insights into 5' flap DNA unwinding and incision by the human FAN1 dimer

Area of Science:

• Biochemistry
• Structural Biology
• Genomics

Background:

• Human FAN1 is a DNA nuclease critical for processing DNA interstrand crosslinks (ICLs).
• FAN1 plays a dual role in maintaining genomic stability and influencing cancer drug resistance.

Purpose of the Study:

• To elucidate the structural mechanisms of human FAN1 in recognizing and processing DNA lesions.
• To understand how FAN1's structure relates to its function in DNA repair and drug resistance.

Main Methods:

• X-ray crystallography was used to determine the structures of human FAN1 complexed with a 5' flap DNA substrate.
• Biochemical experiments were performed to validate structure-informed mutations and their impact on nuclease activity.

Main Results:

• Three crystal structures reveal FAN1 forms a head-to-tail dimer to bind and process ICLs.
• The dimer structure explains DNA lesion localization, orientation, and unwinding of a 5' flap for incision.
• Mutations disrupting dimerization or DNA unwinding significantly impair FAN1's nuclease activity.

Conclusions:

• The study reveals a unique dimeric mechanism for FAN1-mediated DNA incision.
• Structural insights explain FAN1's role in organ protection and cancer drug resistance.
• Understanding FAN1 structure-DNA interactions is key to its cellular functions.