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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC San Francisco Electronic Theses and Dissertations (2020)

Nuclear actin filaments and actin regulators play a role in the DNA repair process.

The branched actin nucleator Arp2/3 has been identified as one such actin regulator and was found to localize to DNA double-stranded break sites and play a role in efficient homology-directed repair. Arp2/3’s cytoplasmic activities have been well-documented and studied, but its presence in the nucleus is only beginning to be understood. We asked whether Arp2/3 was binding directly to DNA for its role in DNA repair and whether it also played a role in the non-homologous end joining DNA repair pathway. We find that Arp2/3 binds directly to DNA and that binding is facilitated by its p41 subunit, with a preference for the p41b isoform. Additionally, this binding is mutually exclusive of Arp2/3’s ability to bind the VCA domain of its activator, leading to Arp2/3’s actin nucleating abilities remaining intact. In addition to the previously reported role of Arp2/3 in homology-directed repair, we present evidence that Arp2/3 is also required for effective non-homologous end joining.

    Cover page: Arp2/3 directly interacts with DNA through the p41 subunit and is involved in the non-homologous end joining repair pathway
    • Article
    • Peer Reviewed
    UC San Francisco Previously Published Works (2015)
    Actin filaments assemble inside the nucleus in response to multiple cellular perturbations, including heat shock, protein misfolding, integrin engagement, and serum stimulation. We find that DNA damage also generates nuclear actin filaments-detectable by phalloidin and live-cell actin probes-with three characteristic morphologies: (i) long, nucleoplasmic filaments; (ii) short, nucleolus-associated filaments; and (iii) dense, nucleoplasmic clusters. This DNA damage-induced nuclear actin assembly requires two biologically and physically linked nucleation factors: Formin-2 and Spire-1/Spire-2. Formin-2 accumulates in the nucleus after DNA damage, and depletion of either Formin-2 or actin's nuclear import factor, importin-9, increases the number of DNA double-strand breaks (DSBs), linking nuclear actin filaments to efficient DSB clearance. Nuclear actin filaments are also required for nuclear oxidation induced by acute genotoxic stress. Our results reveal a previously unknown role for nuclear actin filaments in DNA repair and identify the molecular mechanisms creating these nuclear filaments.
      Cover page: DNA damage induces nuclear actin filament assembly by Formin-2 and Spire-½ that promotes efficient DNA repair
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