Structural mechanism of DNA interstrand cross-link unhooking by the bacterial FAN1 nuclease.Jin, H., Roy, U., Lee, G., Scharer, O.D., Cho, Y.
(2018) J Biol Chem 293: 6482-6496
- PubMed: 29514982
- DOI: 10.1074/jbc.RA118.002171
- Primary Citation of Related Structures:
5Z6W, 5Y7Q, 5Y7G
- PubMed Abstract:
DNA interstrand cross-links (ICLs) block the progress of the replication and transcription machineries and can weaken chromosomal stability, resulting in various diseases. FANCD2-FANCI-associated nuclease (FAN1) is a conserved structure-specific nucl ...
DNA interstrand cross-links (ICLs) block the progress of the replication and transcription machineries and can weaken chromosomal stability, resulting in various diseases. FANCD2-FANCI-associated nuclease (FAN1) is a conserved structure-specific nuclease that unhooks DNA ICLs independently of the Fanconi anemia pathway. Recent structural studies have proposed two different mechanistic features for ICL unhooking by human FAN1: a specific basic pocket that recognizes the terminal phosphate of a 1-nucleotide (nt) 5' flap or FAN1 dimerization. Herein, we show that despite lacking these features, Pseudomonas aeruginosa FAN1 ( Pa FAN1) cleaves substrates at ∼3-nt intervals and resolves ICLs. Crystal structures of Pa FAN1 bound to various DNA substrates revealed that its conserved basic Arg/Lys patch comprising Arg-228 and Lys-260 recognizes phosphate groups near the 5' terminus of a DNA substrate with a 1-nt flap or a nick. Substitution of Lys-260 did not affect Pa FAN1's initial endonuclease activity but significantly decreased its subsequent exonuclease activity and ICL unhooking. The Arg/Lys patch also interacted with phosphates at a 3-nt gap, and this interaction could drive movement of the scissile phosphates into the Pa FAN1-active site. In human FAN1, the ICL-resolving activity was not affected by individual disruption of the Arg/Lys patch or basic pocket. However, simultaneous substitution of both FAN1 regions significantly reduced its ICL-resolving activity, suggesting that these two basic regions play a complementary role in ICL repair. On the basis of these findings, we propose a conserved role for two basic regions in FAN1 to guide ICL unhooking and to maintain genomic stability.
From the Department of Life Science, Pohang University of Science and Technology, Pohang, Kyungbook 37673, South Korea, firstname.lastname@example.org.