Lack of DNA polymerase μ affects the kinetics of DNA double-strand break repair and impacts on cellular senescence.
The specialised DNA polymerase μ (pol μ) affects a sub-class of immunoglobulin genes rearrangements and haematopoietic development in vivo. These effects appear linked to double-strand breaks (DSBs) repair, but it is still unclear how and to what extent pol μ intervenes in this process. Using high-resolution quantitative imaging of DNA damage in irradiated wild-type and pol μ⁻(/)⁻ mouse embryonic fibroblasts (MEFs) we show that lack of pol μ results in delayed DSB repair kinetics and in persistent DNA damage. DNA damage triggers cellular senescence, and this response is thought to suppress cancer. Independent investigations either report or not a proliferative decline for MEFs lacking pol μ. Here we show pronounced senescence in pol μ⁻(/)⁻ MEFs, associated with high levels of the tumor-suppressor p16(INK4A) and the DNA damage response kinase CHK2. Importantly, cellular senescence is induced by culture stress and exacerbated by low doses of irradiation in pol μ⁻(/)⁻ MEFs. We also found that low doses of irradiation provoke delayed immortalisation in MEFs lacking pol μ. Pol μ⁻(/)⁻ MEFs thus exhibit a robust anti-proliferative defence in response to irreparable DNA damage. These findings indicate that sub-optimal DSB repair, due to the absence of an auxiliary DNA damage repair factor, can impact on cell fitness and thereby on cell fate.
Institut Pasteur, Departement d'Immunologie, Paris, France.
Romain
R
Chayot
Anne
A
Danckaert
Benjamin
B
Montagne
Miria
M
Ricchetti
D000818:Animals; D002454:Cell Differentiation / Q000528:radiation effects; D002460:Cell Line; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D016922:Cellular Senescence / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects; D004259:DNA-Directed DNA Polymerase / Q000172:deficiency*; D004307:Dose-Response Relationship, Radiation; D007700:Kinetics; D051379:Mice
C407743:DNA polymerase mu; D004259:DNA-Directed DNA Polymerase