Impeding the single-strand annealing pathway of DNA double-strand break repair by withaferin A-mediated FANCA degradation

DNA Repair (Amst). 2019 May:77:10-17. doi: 10.1016/j.dnarep.2019.02.010. Epub 2019 Feb 27.


FANCA is a key player in the canonical Fanconi anemia (FA) repair pathway. We have recently shown that FANCA also plays an important role in the single-strand annealing sub-pathway (SSA) of DNA double-strand break (DSB) repair by biochemically catalyzing single-strand annealing. Here, we report that a steroidal lactone withaferin A (WA) specifically impedes SSA repair by promoting FANCA downregulation at a sub-micromolar concentration range. We find that WA causes FANCA downregulation post-translationally in a proteasome-dependent manner. This WA-mediated downregulation is achieved through HSP90 inhibition and disruption of the FANCA-HSP90 interaction. WA-mediated FANCA degradation significantly reduces cellular SSA repair, abolishes FANCD2 monoubiquitination, elevates sensitivity to mitomycin C, and results in accumulation of DSBs. Importantly, the WA-induced defect in SSA repair is highly dependent on the absence of FANCA protein and overexpression of exogenous WT-FANCA protein in WA-treated cells significantly complements the repair defect.

Keywords: Double strand break repair; FANCA; Fanconi anemia; Single strand annealing.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • DNA Breaks, Double-Stranded / drug effects*
  • DNA Repair / drug effects*
  • DNA Repair / genetics
  • Fanconi Anemia Complementation Group A Protein / metabolism*
  • HSP90 Heat-Shock Proteins / metabolism
  • Humans
  • Proteasome Endopeptidase Complex / metabolism
  • Proteolysis / drug effects*
  • Ubiquitination / drug effects
  • Ubiquitination / genetics
  • Withanolides / pharmacology*


  • Fanconi Anemia Complementation Group A Protein
  • HSP90 Heat-Shock Proteins
  • Withanolides
  • Proteasome Endopeptidase Complex
  • withaferin A