UV-triggered p21 degradation facilitates damaged-DNA replication and preserves genomic stability

Abstract

Although many genotoxic treatments upregulate the cyclin kinase inhibitor p21, agents such as UV irradiation trigger p21 degradation. This suggests that p21 blocks a process relevant for the cellular response to UV. Here, we show that forced p21 stabilization after UV strongly impairs damaged-DNA replication, which is associated with permanent deficiencies in the recruitment of DNA polymerases from the Y family involved in translesion DNA synthesis), with the accumulation of DNA damage markers and increased genomic instability. Remarkably, such noxious effects disappear when disrupting the proliferating cell nuclear antigen (PCNA) interacting motif of stable p21, thus suggesting that the release of PCNA from p21 interaction is sufficient to allow the recruitment to PCNA of partners (such as Y polymerases) relevant for the UV response. Expression of degradable p21 only transiently delays early replication events and Y polymerase recruitment after UV irradiation. These temporary defects disappear in a manner that correlates with p21 degradation with no detectable consequences on later replication events or genomic stability. Together, our findings suggest that the biological role of UV-triggered p21 degradation is to prevent replication defects by facilitating the tolerance of UV-induced DNA lesions.

Mismatch repair proteins recruited to ultraviolet light-damaged sites lead to degradation of licensing factor Cdt1 in the G1 phase

“…Such an effect is similar to the inhibition of DNA replication by the expression of p21. 59,60 Both replicative DNA polymerases (pol) delta and pol epsilon, and TLS pol kappa are recruited to UV-damaged sites via NER, 44 and pol eta is recruited to UV-damaged sites outside of the S phase and independently of NER. 45 Consistently, high expression of Cdt1 or a PIP-degron Cdt1 mutant prevents recruitment of the TLS DNA polymerases pol kappa and pol eta to UV-damaged sites.…”

The cell death and DNA damages caused by the Tet-On regulating HSV-tk/GCV suicide gene system in MCF-7 cells

“…p21 CIP/WAF1 (cyclin-dependent kinase inhibitor, CKI) belongs to the Cip/Kip cyclin-dependent kinase inhibitor family and it plays a role in cell cycle and DNA damage response. In addition, p21 CIP/ WAF1 can also be combined with PCNA to inhibit its biological functions [11][12][13]. Typically, p53 is the main downstream molecular target of p21 in DNA damage repair pathway.…”

Rad51 recombinase prevents Mre11 nuclease-dependent degradation and excessive PrimPol-mediated elongation of nascent DNA after UV irradiation

“…GFP-proliferating cell nuclear antigen, GFP-Polη, and GFP-Rev1 were gifts from M. C. Cardoso, Max Delbrück Center for Molecular Medicine, Berlin (53), A. Lehmann, University of Sussex, Brighton, United Kingdom (54), and E. Friedberg, University of Texas Southwestern Medical Center, Dallas (55), respectively. UV-C irradiation was performed as described by Mansilla et al (56) and is detailed in SI Materials and Methods. Other reagents used in this study were mirin (catalog no.…”

“…The quantification of specialized Y polymerases and 53BP1 foci was performed as previously described (56) and is detailed in SI Materials and Methods. Primary antibodies were α-BrdU (catalog no.…”