The Kub5-Hera/RPRD1B interactome: a novel role in preserving genetic stability by regulating DNA mismatch repair

Nucleic Acids Res. 2016 Feb 29;44(4):1718-31. doi: 10.1093/nar/gkv1492. Epub 2016 Jan 26.


Ku70-binding protein 5 (Kub5)-Hera (K-H)/RPRD1B maintains genetic integrity by concomitantly minimizing persistent R-loops and promoting repair of DNA double strand breaks (DSBs). We used tandem affinity purification-mass spectrometry, co-immunoprecipitation and gel-filtration chromatography to define higher-order protein complexes containing K-H scaffolding protein to gain insight into its cellular functions. We confirmed known protein partners (Ku70, RNA Pol II, p15RS) and discovered several novel associated proteins that function in RNA metabolism (Topoisomerase 1 and RNA helicases), DNA repair/replication processes (PARP1, MSH2, Ku, DNA-PKcs, MCM proteins, PCNA and DNA Pol δ) and in protein metabolic processes, including translation. Notably, this approach directed us to investigate an unpredicted involvement of K-H in DNA mismatch repair (MMR) where K-H depletion led to concomitant MMR deficiency and compromised global microsatellite stability. Mechanistically, MMR deficiency in K-H-depleted cells was a consequence of reduced stability of the core MMR proteins (MLH1 and PMS2) caused by elevated basal caspase-dependent proteolysis. Pan-caspase inhibitor treatment restored MMR protein loss. These findings represent a novel mechanism to acquire MMR deficiency/microsatellite alterations. A significant proportion of colon, endometrial and ovarian cancers exhibit k-h expression/copy number loss and may have severe mutator phenotypes with enhanced malignancies that are currently overlooked based on sporadic MSI+ screening.

Publication types

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

MeSH terms

  • Antigens, Nuclear / genetics
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • DNA Breaks, Double-Stranded
  • DNA Mismatch Repair / genetics*
  • DNA Topoisomerases, Type I / genetics
  • DNA-Binding Proteins / genetics
  • Genomic Instability*
  • HeLa Cells
  • Humans
  • Ku Autoantigen
  • Multiprotein Complexes / genetics
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Neoplasms / genetics*
  • Neoplasms / metabolism
  • RNA Helicases / genetics
  • RNA Polymerase II / genetics
  • Repressor Proteins / genetics


  • Antigens, Nuclear
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Multiprotein Complexes
  • Neoplasm Proteins
  • RPRD1A protein, human
  • RPRD1B protein, human
  • Repressor Proteins
  • RNA Polymerase II
  • Xrcc6 protein, human
  • RNA Helicases
  • Ku Autoantigen
  • DNA Topoisomerases, Type I