title: Lack of DNA polymerase theta (POLQ) radiosensitizes bone marrow stromal cells in vitro and increases reticulocyte micronuclei after total-body irradiation.
abstract: Abstract Mammalian POLQ (pol theta) is a specialized DNA polymerase with an unknown function in vivo. Roles have been proposed in chromosome stability, as a backup enzyme in DNA base excision repair, and in somatic hypermutation of immunoglobulin genes. The purified enzyme can bypass AP sites and thymine glycol. Mice defective in POLQ are viable and have been reported to have elevated spontaneous and radiation-induced frequencies of micronuclei in circulating red blood cells. To examine the potential roles of POLQ in hematopoiesis and in responses to oxidative stress responses, including ionizing radiation, bone marrow cultures and marrow stromal cell lines were established from Polq(+/+) and Polq(-/-) mice. Aging of bone marrow cultures was not altered, but Polq(-/-) cells were more sensitive to gamma radiation than were Polq(+/+) cells. The D(0) was 1.38 +/- 0.06 Gy for Polq(+/+) cells compared to 1.27 +/- 0.16 and 0.98 +/- 0.10 Gy (P = 0.032) for two Polq(-/-) clones. Polq(-/-) cells were moderately more sensitive to bleomycin than Polq(+/+) cells and were not hypersensitive to paraquat or hydrogen peroxide. ATM kinase activation appeared to be normal in gamma-irradiated Polq(-/-) cells. Inhibition of ATM kinase activity increased the radiosensitivity of Polq(+/+) cells slightly but did not affect Polq(-/-) cells. Polq(-/-) mice had more spontaneous and radiation-induced micronucleated reticulocytes than Polq+/+ and (+/-) mice. The sensitivity of POLQ-defective bone marrow stromal cells to ionizing radiation and bleomycin and the increase in micronuclei in red blood cells support a role for this DNA polymerase in cellular tolerance of DNA damage that can lead to double-strand DNA breaks.
authors.affiliation: Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Julie P
authors.initials: JP
authors.lastname: Goff
authors.forename: Donna S
authors.initials: DS
authors.lastname: Shields
authors.forename: Mineaki
authors.initials: M
authors.lastname: Seki
authors.forename: Serah
authors.initials: S
authors.lastname: Choi
authors.forename: Michael W
authors.initials: MW
authors.lastname: Epperly
authors.forename: Tracy
authors.initials: T
authors.lastname: Dixon
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bakkenist
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Dertinger
authors.forename: Dorothea K
authors.initials: DK
authors.lastname: Torous
authors.forename: John
authors.initials: J
authors.lastname: Wittschieben
authors.forename: Richard D
authors.initials: RD
authors.lastname: Wood
authors.forename: Joel S
authors.initials: JS
authors.lastname: Greenberger
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D048629:Micronuclei, Chromosome-Defective / Q000528:radiation effects*; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000502:physiology*; D012156:Reticulocytes / Q000166:cytology / Q000528:radiation effects*; D014916:Whole-Body Irradiation; D000097462:DNA Polymerase theta
chemical_list: D004259:DNA-Directed DNA Polymerase; D000097462:DNA Polymerase theta