Abstract
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.
Original language | English |
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Pages (from-to) | 1337-44 |
Number of pages | 8 |
Journal | DNA repair |
Volume | 4 |
Issue number | 11 |
DOIs | |
Publication status | Published - 21 Nov 2005 |
Externally published | Yes |
Keywords
- Animals
- Apoptosis/genetics
- Cell Death/radiation effects
- Cell Division/radiation effects
- Cells, Cultured
- DNA Damage/genetics
- DNA Repair/genetics
- DNA Repair Enzymes/genetics
- DNA Replication/radiation effects
- DNA-Binding Proteins/genetics
- Genetic Predisposition to Disease
- Keratinocytes/metabolism
- Mice
- Poly-ADP-Ribose Binding Proteins
- Radiation Tolerance
- S Phase/genetics
- Signal Transduction/genetics
- Skin Neoplasms/etiology
- Ultraviolet Rays
- Xeroderma Pigmentosum Group A Protein/genetics