Identification of a minimal sequence of p21 that sensitizes tumor cells to DNA damaging agents.

2.DE LA VEGA MB , MANSILLA SF , BERTOLIN A , GOTTIFREDI V

Salta

Congreso; LV Anual Conference. SAIB ?PABMB (Sociedad argentina de investigaciones bioquímicas- Pan American Society of Biochemistry and Molecular Biology); 2019

SAIB-PABMB

DNA-damaging agents used in traditional chemotherapy are cytotoxic by interfering with DNA replication. These agents target cells with a high proliferation rate by generating lesions in the DNA that impair replication and cause cell death. The efficacy of anticancer treatments is, however, highly influenced by the cellular capacity to respond to DNA damage. One central mechanism that enables cancer cells to survive is Translesion DNA Synthesis (TLS). This process involves specialized DNA polymerases that synthesize a short patch of DNA across the lesion, a situation where replicative DNA polymerases would normally stall. Therefore, inhibiting TLS would be deleterious to these cells when used in combination with DNA-damaging agents. Our group has previously identified the cyclin-CDK inhibitor p21 as the first global inhibitor of TLS. A stabilized version of p21 (sp21) can inhibit the recruitment of TLS polymerases to replication factories after DNA damage without interfering with normal DNA replication, and this is dependent on its PCNA-binding domain. In this work, we have found that a smaller version of p21, which contains only its PCNA-Interacting Region (sPIR), is sufficient to robustly inhibit the recruitment of TLS polymerases to replication factories post ultraviolet (UV) radiation. By using a non-replicative lentivirus system as an overexpression tool, we have found that the sPIR increases cell death in the context of many DNA-damage inductors such as UV, cisplatin, and hydroxyurea. Lately, we have also found that, in many tumor cell lines, co-inhibition of TLS and Chk1, a protein with a pivotal role in the intra S-phase checkpoint, efficiently synergize to enhance replicative stress and cell death. Our data suggest that the PIR domain of p21 is a versatile tool with potential therapeutic utility.