NUCKS1 is a novel RAD51AP1 paralog important for homologous recombination and genome stability

Nucleic Acids Res. 2015 Nov 16;43(20):9817-34. doi: 10.1093/nar/gkv859. Epub 2015 Aug 31.


NUCKS1 (nuclear casein kinase and cyclin-dependent kinase substrate 1) is a 27 kD chromosomal, vertebrate-specific protein, for which limited functional data exist. Here, we demonstrate that NUCKS1 shares extensive sequence homology with RAD51AP1 (RAD51 associated protein 1), suggesting that these two proteins are paralogs. Similar to the phenotypic effects of RAD51AP1 knockdown, we find that depletion of NUCKS1 in human cells impairs DNA repair by homologous recombination (HR) and chromosome stability. Depletion of NUCKS1 also results in greatly increased cellular sensitivity to mitomycin C (MMC), and in increased levels of spontaneous and MMC-induced chromatid breaks. NUCKS1 is critical to maintaining wild type HR capacity, and, as observed for a number of proteins involved in the HR pathway, functional loss of NUCKS1 leads to a slow down in DNA replication fork progression with a concomitant increase in the utilization of new replication origins. Interestingly, recombinant NUCKS1 shares the same DNA binding preference as RAD51AP1, but binds to DNA with reduced affinity when compared to RAD51AP1. Our results show that NUCKS1 is a chromatin-associated protein with a role in the DNA damage response and in HR, a DNA repair pathway critical for tumor suppression.

Publication types

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

MeSH terms

  • Cell Line
  • Chromatin / metabolism
  • Chromosome Aberrations
  • DNA / metabolism
  • DNA Damage
  • DNA Replication
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / physiology
  • Genomic Instability*
  • HeLa Cells / physiology
  • Humans
  • Mitomycin / pharmacology
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Nuclear Proteins / physiology*
  • Phosphoproteins / chemistry
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism
  • Phosphoproteins / physiology*
  • Phosphorylation / radiation effects
  • RNA-Binding Proteins
  • Rad51 Recombinase / metabolism
  • Recombinational DNA Repair*
  • S Phase / radiation effects
  • Sequence Homology, Amino Acid
  • X-Rays


  • Chromatin
  • DNA-Binding Proteins
  • NUCKS1 protein, human
  • Nuclear Proteins
  • Phosphoproteins
  • RAD51AP1 protein, human
  • RNA-Binding Proteins
  • Mitomycin
  • DNA
  • Rad51 Recombinase