Human KIAA1018/FAN1 localizes to stalled replication forks via its ubiquitin-binding domain

Abstract

Genome maintenance pathways correct aberrations in DNA that would be deleterious to the organism. A crucial element of many genome maintenance processes is the ability to degrade DNA that either contains errors or obscures useful substrates for recombination and/or repair by means of nucleases. We have examined a putative nuclease that has heretofore been unreported, KIAA1018/FAN1. This protein contains a predicted ubiquitin-binding zinc finger domain (UBZ) near its N-terminus and an endonuclease-like fold near its C-terminus. Here we describe that FAN1 is a nuclear protein and forms DNA-damage-induced foci, which appear to be at stalled replication forks as denoted by RPA colocalization. Localization of FAN1 to sites of damage is dependent upon its UBZ domain. In addition, knockdown of FAN1 by RNA interference leads to increased sensitivity to interstrand crosslinking agents and accumulation of abnormal chromosomes. FAN1 may be an important new player in the maintenance of genome stability.

Spartan/C1orf124 is important to prevent UV-induced mutagenesis

“…13,14 In particular, ubiquitin-binding zinc-finger 4 (UBZ4) is commonly found in proteins that localize to sites of DNA damage. [15][16][17][18][19][20][21][22][23][24][25][26] To find potential regulators of DNA damage response, we performed a bioinformatics search for uncharacterized proteins containing UBZ4 domains. We noted that a human protein C1orf124 (NP_114407), which was recently named Spartan, 27 contains a PIP box and UBZ4, similarly to TLS polymerases.…”

Rescue of replication failure by Fanconi anaemia proteins

“…One such nuclease is FAN1, discovered independently by five groups that have reported congruent observations (Kratz et al 2010; Liu et al 2010; MacKay et al 2010; Shereda et al 2010; Smogorzewska et al 2010): FAN1 stands for FANCD2-associated nuclease. The protein is necessary for chromosome stability and for cellular tolerance to cisplatin and mitomycin C. In cells treated with ICL-inducing agents, FAN1 forms nuclear foci that colocalise with FANCD2 and binds to the monoubiquitinated form of FANCD2.…”

“…This signalling event has been proposed to stabilise the ubiquitinated FANCI–FANCD2 complex in chromatin, which in turn allows recruitment of DNA repair factors such as the nuclease FAN1 at damaged sites (Kratz et al 2010; Liu et al 2010; MacKay et al 2010; Shereda et al 2010; Smogorzewska et al 2010; Stoepker et al 2011; Yoshikiyo et al 2010). …”

“…It contains an amino-terminal ubiquitin-binding motif, a RAD18-like CCHC zinc finger known as UBZ domain and a carboxy terminal VRR-nuc domain (virus-type replication-repair nuclease domain). The UBZ domain is both necessary and sufficient for interaction with FANCD2 and for targeting of FAN1 to DNA repair sites (Kratz et al 2010; Liu et al 2010; MacKay et al 2010; Shereda et al 2010). FAN1 exhibits 5′ flap endonuclease and 5′–3′ exonuclease activities and participates in DNA repair mechanisms dependent on homologous recombination (Kratz et al 2010; Liu et al 2010; MacKay et al 2010; Smogorzewska et al 2010).…”

The Fanconi anemia pathway in replication stress and DNA crosslink repair

“…The structure specific endonuclease, FAN1 (FANCD2-associated nuclease), contains an amino-terminal ubiquitin binding zinc finger (UBZ) domain that targets FAN1 to monoubiquitinated FANCD2 (Figure 1) (Kratz et al 2010; Liu et al 2010; MacKay et al 2010; Shereda et al 2010; Smogorzewska et al 2010). FAN1 possesses 5′ flap endonuclease activities and FAN1 recruitment to FANCD2 is required for resistance to ICLs induced by MMC and cisplatin.…”