title: A hot spot for RAD51C interactions revealed by a peptide that sensitizes cells to cisplatin.
abstract: DNA repair via the homologous recombination pathway requires the recombinase RAD51 and, in vertabrates, five RAD51 paralogs. The paralogs form two complexes in solution, a XRCC3/RAD51C heterodimer and a RAD51B/RAD51C/RAD51D/XRCC2 heterotetramer. Mutation of any one of the five paralog genes prevents subnuclear assembly of recombinase at damaged sites and renders cells 30-100 fold sensitive to DNA cross-linking drugs. Phage display was used to isolate peptides that bind the paralog XRCC3. Sequences of binding peptides showed similarity to residues 14-25 of RAD51C protein. Point mutations in this region of RAD51C altered its interaction with both XRCC3 and RAD51B in a two-hybrid system. A synthetic peptide composed of residues 14-25 of RAD51C fused to a membrane transduction sequence [protein transduction domain 4 (PTD4)], inhibited subnuclear assembly of RAD51 recombinase, and sensitized Chinese hamster ovary cells to cisplatin when added to growth medium. These results suggest that residues 14-25 of RAD51C contribute to a "hot spot" used in both XRCC3-RAD51C and RAD51B-RAD51C interactions. Peptide-based inhibition of homologous recombination may prove useful for improving the efficacy of existing cancer therapies.
authors.affiliation: Department of Radiation and Cellular Oncology, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Philip P
authors.initials: PP
authors.lastname: Connell
authors.forename: Nazli
authors.initials: N
authors.lastname: Siddiqui
authors.forename: Sara
authors.initials: S
authors.lastname: Hoffman
authors.forename: Audrey
authors.initials: A
authors.lastname: Kuang
authors.forename: Emir-Assan
authors.initials: EA
authors.lastname: Khatipov
authors.forename: Ralph R
authors.initials: RR
authors.lastname: Weichselbaum
authors.forename: Douglas K
authors.initials: DK
authors.lastname: Bishop
mesh_terms: D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017104:Bacteriophage M13 / Q000235:genetics; D002945:Cisplatin / Q000494:pharmacology*; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019151:Peptide Library; D010455:Peptides / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D019151:Peptide Library; D010455:Peptides; C448305:RAD51C protein, human; D011993:Recombinant Fusion Proteins; C110901:X-ray repair cross complementing protein 3; D002945:Cisplatin