title: BCR/ABL and other kinases from chronic myeloproliferative disorders stimulate single-strand annealing, an unfaithful DNA double-strand break repair.
abstract: Myeloproliferative disorders (MPD) are stem cell-derived clonal diseases arising as a consequence of acquired aberrations in c-ABL, Janus-activated kinase 2 (JAK2), and platelet-derived growth factor receptor (PDGFR) that generate oncogenic fusion tyrosine kinases (FTK), including BCR/ABL, TEL/ABL, TEL/JAK2, and TEL/PDGFbetaR. Here, we show that FTKs stimulate the formation of reactive oxygen species and DNA double-strand breaks (DSB) both in hematopoietic cell lines and in CD34(+) leukemic stem/progenitor cells from patients with chronic myelogenous leukemia (CML). Single-strand annealing (SSA) represents a relatively rare but very unfaithful DSB repair mechanism causing chromosomal aberrations. Using a specific reporter cassette integrated into genomic DNA, we found that BCR/ABL and other FTKs stimulated SSA activity. Imatinib-mediated inhibition of BCR/ABL abrogated this effect, implicating a kinase-dependent mechanism. Y253F, E255K, T315I, and H396P mutants of BCR/ABL that confer imatinib resistance also stimulated SSA. Increased expression of either nonmutated or mutated BCR/ABL kinase, as is typical of blast phase cells and very primitive chronic phase CML cells, was associated with higher SSA activity. BCR/ABL-mediated stimulation of SSA was accompanied by enhanced nuclear colocalization of RAD52 and ERCC1, which play a key role in the repair. Taken together, these findings suggest a role of FTKs in causing disease progression in MPDs by inducing chromosomal instability through the production of DSBs and stimulation of SSA repair.
authors.affiliation: Department of Microbiology and Immunology, Temple University, Philadelphia, Pennsylvania 19140, USA.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Cramer
authors.forename: Margaret
authors.initials: M
authors.lastname: Nieborowska-Skorska
authors.forename: Mateusz
authors.initials: M
authors.lastname: Koptyra
authors.forename: Artur
authors.initials: A
authors.lastname: Slupianek
authors.forename: Emir Tyrone P
authors.initials: ET
authors.lastname: Penserga
authors.forename: Connie J
authors.initials: CJ
authors.lastname: Eaves
authors.forename: Walter
authors.initials: W
authors.lastname: Aulitzky
authors.forename: Tomasz
authors.initials: T
authors.lastname: Skorski