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Ahmed, E.A.* ; Vélaz, E.* ; Rosemann, M. ; Gilbertz, K.P.* ; Scherthan, H.*

DNA repair kinetics in SCID mice Sertoli cells and DNA-PKcs-deficient mouse embryonic fibroblasts.

Chromosoma, DOI: 10.1007/s00412-016-0590-9 (2016)
DOI PMC
Open Access Green as soon as Postprint is submitted to ZB.
Noncycling and terminally differentiated (TD) cells display differences in radiosensitivity and DNA damage response. Unlike other TD cells, Sertoli cells express a mixture of proliferation inducers and inhibitors in vivo and can reenter the cell cycle. Being in a G1-like cell cycle stage, TD Sertoli cells are expected to repair DSBs by the error-prone nonhomologous end-joining pathway (NHEJ). Recently, we have provided evidence for the involvement of Ku-dependent NHEJ in protecting testis cells from DNA damage as indicated by persistent foci of the DNA double-strand break (DSB) repair proteins phospho-H2AX, 53BP1, and phospho-ATM in TD Sertoli cells of Ku70-deficient mice. Here, we analyzed the kinetics of 53BP1 foci induction and decay up to 12 h after 0.5 Gy gamma irradiation in DNA-PKcs-deficient (Prkdc (scid) ) and wild-type Sertoli cells. In nonirradiated mice and Prkdc (scid) Sertoli cells displayed persistent DSBs foci in around 12 % of cells and a fivefold increase in numbers of these DSB DNA damage-related foci relative to the wild type. In irradiated mice, Prkdc (scid) Sertoli cells showed elevated levels of DSB-indicating foci in 82 % of cells 12 h after ionizing radiation (IR) exposure, relative to 52 % of irradiated wild-type Sertoli cells. These data indicate that Sertoli cells respond to and repair IR-induced DSBs in vivo, with repair kinetics being slow in the wild type and inefficient in Prkdc (scid) . Applying the same dose of IR to Prdkc (-/-) and Ku (-/-) mouse embryonic fibroblast (MEF) cells revealed a delayed induction of 53BP1 DSB-indicating foci 5 min post-IR in Prdkc (-/-) cells. Inefficient DSB repair was evident 7 h post-IR in DNA-PKcs-deficient cells, but not in Ku (-/-) MEFs. Our data show that quiescent Sertoli cells repair genotoxic DSBs by DNA-PKcs-dependent NEHJ in vivo with a slower kinetics relative to somatic DNA-PKcs-deficient cells in vitro, while DNA-PKcs deficiency caused inefficient DSB repair at later time points post-IR in both conditions. These observations suggest that DNA-PKcs contributes to the fast and slow repair of DSBs by NHEJ.
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Publication type Article: Journal article
Document type Scientific Article
Corresponding Author
Keywords 53bp1 ; Dna-pkcs ; Dsb Repair ; Ku70 ; Nhej ; Sertoli Cells
ISSN (print) / ISBN 0009-5915
e-ISSN 1432-0886
Journal Chromosoma
Publisher Springer
Non-patent literature Publications
Reviewing status Peer reviewed
Institute(s) Institute of Radiation Biology (ISB)