FANCA Promotes DNA Double-Strand Break Repair by Catalyzing Single-Strand Annealing and Strand Exchange

Abstract

FANCA is a component of the Fanconi anemia (FA) core complex that activates DNA interstrand crosslink repair by monoubiquitination of FANCD2. Here, we report that purified FANCA protein catalyzes bidirectional single-strand annealing (SA) and strand exchange (SE) at a level comparable to RAD52, while a disease-causing FANCA mutant, F1263Δ, is defective in both activities. FANCG, which directly interacts with FANCA, dramatically stimulates its SA and SE activities. Alternatively, FANCB, which does not directly interact with FANCA, does not stimulate this activity. Importantly, five other patient-derived FANCA mutants also exhibit deficient SA and SE, suggesting that the biochemical activities of FANCA are relevant to the etiology of FA. A cell-based DNA double-strand break (DSB) repair assay demonstrates that FANCA plays a direct role in the single-strand annealing sub-pathway (SSA) of DSB repair by catalyzing SA, and this role is independent of the canonical FA pathway and RAD52.

Fanconi anemia proteins are required to maintain nucleolar homeostasis

“…In addition, we unveiled a new, FANC pathway independent, role of FANCA demonstrating that its loss-of-function is associated to defects in rDNA transcription and mRNA translation that we failed to observe in other FANC pathway-deficient cells. These observations strengthen several previous observations demonstrating specific roles of the individual FANC proteins, and FANCA in particular, regardless of their participation to the FANC pathway (Adachi et al, 2002;Benitez et al, 2018;Nepal et al, 2018). In all panels, statistical significance was assessed with two-tailed unpaired Student's t-tests by using GraphPad on-line software (*p<0.05, **p<0.01, ***p<0.005).…”

Cooperation of the ATM and Fanconi Anemia/BRCA Pathways in Double-Strand Break End Resection

“…Monoubiquitinated FANCD2, a downstream product of the FA pathway, may bind and stimulate the end resection activity of CtIP. Recent studies also indicate that the FANCA protein can promote the process of SSA (Benitez et al, 2018) and may thereby positively regulate end resection. Accordingly, inactivation of both the ATM and FA pathways appears to further reduce DSB end resection.…”

Mechanisms preventing Break-Induced Replication during repair of two-ended DNA double-strand breaks

“…Rad52 is highly conserved but in many eukaryotes it plays less prominent role in HR. In these organisms additional annealing enzymes evolved with a role in HR such as FANCA in human, annealing helicase SMARCAL1 in flies, or the BRCA2 homolog in U. maydis, Bhr2 (Benitez, Liu et al, 2018, Holsclaw & Sekelsky, 2017, Mazloum & Holloman, 2009). With the exception of Rad59, all the proteins studied here are well conserved between yeast and humans.…”