A PP1-binding motif present in BRCA1 plays a role in its DNA repair function

Int J Biol Sci. 2008;4(6):352-61. doi: 10.7150/ijbs.4.352. Epub 2008 Oct 4.

Abstract

Protein phosphatase 1alpha (PP1alpha) regulates phosphorylation of BRCA1, which contains a PP1-binding motif (898)KVTF(901). Mutation of this motif greatly reduces the interaction between BRCA1 and PP1alpha. Here we show that mutation of the PP1-binding motif abolishes the ability of BRCA1 to enhance survival of Brca1-deficient mouse mammary tumor cells after DNA damage. The Rad51 focus formation and comet assays revealed that the DNA repair function of BRCA1 was impaired when the PP1-binding motif was mutated. Analysis of subnuclear localization of GFP-tagged BRCA1 demonstrated that mutation of the PP1-binding motif affected BRCA1 redistribution in response to DNA damage. BRCA1 is required for the formation of Rad51 subnuclear foci after DNA damage. Mutation of the PP1-binding motif in BRCA1 also affected recruitment of Rad51 to sites of DNA damage. Consistent with these findings, knockdown of PP1alpha in BRCA1-proficient cells by small interfering RNA also significantly reduced Rad51 focus formation induced by DNA damage. Further analysis indicated that mutation of the PP1-binding motif compromised BRCA1 activities in homologous recombination. Altogether, our data implicate that interaction with PP1alpha is important for BRCA1 function in DNA repair.

Keywords: BRCA1; DNA repair; protein phosphatase 1.

Publication types

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

MeSH terms

  • Amino Acid Motifs / physiology
  • Animals
  • BRCA1 Protein / analysis
  • BRCA1 Protein / chemistry*
  • BRCA1 Protein / physiology
  • Binding Sites
  • COS Cells
  • Cell Line
  • Chlorocebus aethiops
  • DNA Damage
  • DNA Repair / physiology*
  • Green Fluorescent Proteins / analysis
  • Humans
  • Mammary Neoplasms, Experimental / genetics
  • Mammary Neoplasms, Experimental / pathology
  • Mice
  • Mutation
  • Phosphorylation
  • Protein Phosphatase 1 / metabolism*
  • Rad51 Recombinase / metabolism
  • Recombinant Fusion Proteins / analysis
  • Recombination, Genetic

Substances

  • BRCA1 Protein
  • BRCA1 protein, human
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Rad51 Recombinase
  • Protein Phosphatase 1