title: Interactions involving the Rad51 paralogs Rad51C and XRCC3 in human cells.
abstract: Homologous recombinational repair of DNA double-strand breaks and crosslinks in human cells is likely to require Rad51 and the five Rad51 paralogs (XRCC2, XRCC3, Rad51B/Rad51L1, Rad51C/Rad51L2 and Rad51D/Rad51L3), as has been shown in chicken and rodent cells. Previously, we reported on the interactions among these proteins using baculovirus and two- and three-hybrid yeast systems. To test for interactions involving XRCC3 and Rad51C, stable human cell lines have been isolated that express (His)6-tagged versions of XRCC3 or Rad51C. Ni2+-binding experiments demonstrate that XRCC3 and Rad51C interact in human cells. In addition, we find that Rad51C, but not XRCC3, interacts directly or indirectly with Rad51B, Rad51D and XRCC2. These results argue that there are at least two complexes of Rad51 paralogs in human cells (Rad51C-XRCC3 and Rad51B-Rad51C-Rad51D-XRCC2), both containing Rad51C. Moreover, Rad51 is not found in these complexes. X-ray treatment did not alter either the level of any Rad51 paralog or the observed interactions between paralogs. However, the endogenous level of Rad51C is moderately elevated in the XRCC3-overexpressing cell line, suggesting that dimerization between these proteins might help stabilize Rad51C.
authors.affiliation: Life Sciences Division, 1 Cyclotron Road, Mailstop 70A-1118, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Wiese
authors.forename: David W
authors.initials: DW
authors.lastname: Collins
authors.forename: Joanna S
authors.initials: JS
authors.lastname: Albala
authors.forename: Larry H
authors.initials: LH
authors.lastname: Thompson
authors.forename: Amy
authors.initials: A
authors.lastname: Kronenberg
authors.forename: David
authors.initials: D
authors.lastname: Schild
mesh_terms: D030161:Avian Proteins; D016923:Cell Death; D002460:Cell Line; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000378:metabolism / Q000528:radiation effects; D046911:Macromolecular Substances; D008954:Models, Biological; D011233:Precipitin Tests; D051135:Rad51 Recombinase; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D014965:X-Rays
chemical_list: D030161:Avian Proteins; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; C413002:RAD51B protein, human; C448305:RAD51C protein, human; C112629:RAD51D protein, human; D011993:Recombinant Fusion Proteins; C110901:X-ray repair cross complementing protein 3; C113187:XRCC2 protein, human; C495150:RAD51 protein, Gallus gallus; C495153:RAD51 protein, human; D051135:Rad51 Recombinase