Identification of KIAA1018/FAN1, a DNA Repair Nuclease Recruited to DNA Damage by Monoubiquitinated FANCD2

Abstract

DNA interstrand crosslinks (ICLs) are highly toxic because they block the progression of replisomes. The Fanconi Anemia (FA) proteins, encoded by genes that are mutated in FA, are important for repair of ICLs. The FA core complex catalyzes the monoubiquitination of FANCD2, and this event is essential for several steps of ICL repair. However, how monoubiquitination of FANCD2 promotes ICL repair at the molecular level is unknown. Here, we describe a highly conserved protein, KIAA1018/MTMR15/FAN1, that interacts with, and is recruited to sites of DNA damage by, the monoubiquitinated form of FANCD2. FAN1 exhibits endonuclease activity toward 5' flaps and has 5' exonuclease activity, and these activities are mediated by an ancient VRR_nuc domain. Depletion of FAN1 from human cells causes hypersensitivity to ICLs, defects in ICL repair, and genome instability. These data at least partly explain how ubiquitination of FANCD2 promotes DNA repair.

Cyclin E2 induces genomic instability by mechanisms distinct from cyclin E1

“…Metaphase spreads were then performed as previously described. 57 Data have been pooled from three separate experiments.…”

The role of DNA exonucleases in protecting genome stability and their impact on ageing

“…Furthermore, FAN1 was independently described as a putative nuclease that interacts with FANCD2. Absence of FAN1 was found to increase cellular sensitivity to ICL-inducing agents such as mitomycin C and cisplatin (Liu et al 2010;MacKay et al 2010).…”

“…Alternatively, the structure arising from the first incision may resemble a 5′ flap, which could act as a substrate for the endonuclease activity of FAN1. While there is no difference in the rate of formation of cisplatin-induced or mitomycin C-induced DSBs in a FAN1-depleted background, their disappearance (removal) is slower than in controls (Kratz et al 2010;MacKay et al 2010), suggesting that FAN1 is not required to introduce DSBs, but rather is involved in their repair. Since DSB repair often occurs via homologous recombination (HR), this strongly implies that the FAN1 nuclease is involved in DNA processing during the latter stages of HR, but does not preclude the possibility that FAN1 may act in other as yet undiscovered pathways.…”

“…The multiple nucleolytic abilities of FAN1 imply a multifunctional capacity similar to ExoG or Mre11. Whether the primary role of FAN1 is indeed in ICL repair (Kratz et al 2010;Liu et al 2010;MacKay et al 2010;Smogorzewska et al 2010) or lies in other DNA transactions such as removal of flaps at stalled replication forks remains to be determined.…”

Mammalian mismatch repair: error-free or error-prone?

“…These areas are highly relevant to human health and deserve much closer examination. Analysis of the interactome of MMR proteins [57] indicated that these polypeptides associate with partners that play key roles in other DNA damage-processing pathways, such as the repair of interstrand cross-links [57][58][59][60][61]. The role of MMR in this important metabolic pathway is not understood and deserves attention.…”