title: Degradation of BRCA2 in alkyltransferase-mediated DNA repair and its clinical implications.
abstract: Germ-line mutations in BRCA2 have been linked to early-onset familial breast cancer. BRCA2 is known to play a key role in repairing double-strand breaks. Here, we describe the involvement of BRCA2 in O6-alkylguanine DNA alkyltransferase (AGT)-mediated repair of O6-methylguanine adducts. We show that BRCA2 physically associates and undergoes repair-mediated degradation with AGT. In contrast, BRCA2 with a 29-amino-acid deletion in an evolutionarily conserved domain does not bind to alkylated AGT; the two proteins are not degraded; and mouse embryonic fibroblasts are specifically sensitive to alkylating agents that result in O6-methylguanine adducts. We show that O6-benzylguanine (O6BG), a nontoxic inhibitor of AGT, can also induce BRCA2 degradation. BRCA2 is a viable target for cancer therapy because BRCA2-deficient cells are hypersensitive to chemotherapeutic DNA-damaging agents. We show a marked effect of O6BG pretreatment on cell sensitivity to cisplatin. We also show the efficacy of this approach on a wide range of human tumor cell lines, which suggests that chemosensitization of tumors by targeted degradation of BRCA2 may be an important consideration when devising cancer therapeutics.
authors.affiliation: Mouse Cancer Genetics Program, Center for Cancer Research, and Pathology Histotechnology Laboratory, Science Applications International Corporation-Frederick, Inc., National Cancer Institute at Frederick, Frederick, Maryland 21702, USA.
authors.forename: Subha
authors.initials: S
authors.lastname: Philip
authors.forename: Srividya
authors.initials: S
authors.lastname: Swaminathan
authors.forename: Sergey G
authors.initials: SG
authors.lastname: Kuznetsov
authors.forename: Sreenivas
authors.initials: S
authors.lastname: Kanugula
authors.forename: Kajal
authors.initials: K
authors.lastname: Biswas
authors.forename: Suhwan
authors.initials: S
authors.lastname: Chang
authors.forename: Natalia A
authors.initials: NA
authors.lastname: Loktionova
authors.forename: Diana C
authors.initials: DC
authors.lastname: Haines
authors.forename: Philipp
authors.initials: P
authors.lastname: Kaldis
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Pegg
authors.forename: Shyam K
authors.initials: SK
authors.lastname: Sharan
mesh_terms: D000477:Alkylating Agents; D000595:Amino Acid Sequence; D000818:Animals; D024682:BRCA2 Protein / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair / Q000502:physiology*; D017353:Gene Deletion; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D008769:Methylnitronitrosoguanidine; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000477:Alkylating Agents; D024682:BRCA2 Protein; C106711:BRCA2 protein, mouse; C064976:O(6)-benzylguanine; D008769:Methylnitronitrosoguanidine; D006147:Guanine; C008449:O-(6)-methylguanine; D019853:O(6)-Methylguanine-DNA Methyltransferase