title: Gene conversion is strongly induced in human cells by double-strand breaks and is modulated by the expression of BCL-x(L).
abstract: Homology-directed repair (HDR) of DNA double-strand breaks (DSBs) contributes to the maintenance of genomic stability in rodent cells, and it has been assumed that HDR is of similar importance in DSB repair in human cells. However, some outcomes of homologous recombination can be deleterious, suggesting that factors exist to regulate HDR. We demonstrated previously that overexpression of BCL-2 or BCL-x(L) enhanced the frequency of X-ray-induced TK1 mutations, including loss of heterozygosity events presumed to arise by mitotic recombination. The present study was designed to test whether HDR is a prominent DSB repair pathway in human cells and to determine whether ectopic expression of BCL-x(L) affects HDR. Using TK6-neo cells, we find that a single DSB in an integrated HDR reporter stimulates gene conversion 40-50-fold, demonstrating efficient DSB repair by gene conversion in human cells. Significantly, DSB-induced gene conversion events are 3-4-fold more frequent in TK6 cells that stably overexpress the antiapoptotic protein BCL-X(L). Thus, HDR plays an important role in maintaining genomic integrity in human cells, and ectopic expression of BCL-x(L) enhances HDR of DSBs. This is the first study to highlight a function for BCL-x(L) in modulating DSB repair in human cells.
authors.affiliation: Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Wiese
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Pierce
authors.forename: Stacey S
authors.initials: SS
authors.lastname: Gauny
authors.forename: Maria
authors.initials: M
authors.lastname: Jasin
authors.forename: Amy
authors.initials: A
authors.lastname: Kronenberg
mesh_terms: D002478:Cells, Cultured; D004249:DNA Damage; D004260:DNA Repair; D005785:Gene Conversion; D006801:Humans; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D051020:bcl-X Protein
chemical_list: C494811:BCL2L1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein