Cellular DNA damage responses (DDRs) are induced by unrepaired DNA lesions and constitute a protective back-up system that prevents the expansion of damaged cells. These cellular signaling pathways trigger either growth arrest or cell death and are believed to be major components of an early anti-cancer barrier. Cultures of C57BL/6J keratinocytes with various defects in NER sub-pathways allowed us to follow the kinetics of DDRs in an isogenic background and in the proper (physiologically relevant) target cells, supplementing earlier studies in heterogenic human fibroblasts. In a series of well-controlled parallel experiments we have shown that, depending on the NER deficiency, murine keratinocytes elicited highly selective DDRs. After a dose of UV-B that did not affect wild-type keratinocytes, Xpa-/- keratinocytes (complete NER deficiency) showed a rapid depletion of DNA replicating S-phase cells, a transient increase in quiescent S-phase cells (not replicating DNA), followed by massive apoptosis. Csb-/- keratinocytes (TC-NER deficient) responded by a more sustained increase in QS-phase cells and appeared more resistant to UV-B induced apoptosis than Xpa-/-. In irradiated Xpc-/- keratinocytes (GG-NER deficient) the loss of replicating S-phase cells was associated with a gradual build-up of both QS-phase cells and cells arrested in late-S phase, in complete absence of apoptosis. Our analysis complements and extends previous in vivo investigations and highlights both similarities and differences with earlier fibroblast studies. In vitro cultures of murine keratinocytes provide a new tool to unravel the molecular mechanisms of UV-induced cellular stress responses in great detail and in a physiologically relevant background. This will be essential to fully appreciate the implications of DDRs in tumor suppression and cancer prevention.

Additional Metadata
Keywords Apoptosis, Cell cycle arrest, Global genome repair (GG-NER), Mouse keratinocytes, Nucleotide excision repair (NER), Transcription-coupled repair (TC-NER), Ultraviolet light
Persistent URL dx.doi.org/10.1016/j.dnarep.2005.07.012, hdl.handle.net/1765/60506
Journal D N A Repair
Citation
Stout, G.J, van Oosten, M, Acherrat, F.Z, de Wit, J, Vermeij, W.P, Mullenders, L.H.F, … Backendorf, C.M.P. (2005). Selective DNA damage responses in murine Xpa-/-, Xpc -/- and Csb-/- keratinocyte cultures. D N A Repair, 4(11), 1337–1344. doi:10.1016/j.dnarep.2005.07.012