CDK4/6 INHIBITOR p19INK4d INCREASES THE DNA REPAIR ABILITY IN FIBROBLAST

CÁNEPA, EDUARDO; JULIO, MIGUEL; CERUTI, JULIETA; CARCAGNO, ABEL; GUBERMAN, ALEJANDRA; SCASSA, MARÍA

Bariloche, Argentina

Congreso; XXXIX Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2003

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

The four proteins of the INK4 family posses a similar structure and bind to CDK4/6 with similar affinity driving to a G1 cell cycle arrest, but they are reported to have different biological roles. The aim of this work was to evaluate if p19INK4d induces a second photoprotective response after DNA damage. Northern blot analysis show that p19 is up-regulated after UV irradiation in BHK cells. Levels of p19INK4d mRNA peaked 12 h after UV treatment. This induction resulted dose dependent and started at 5 mJ/cm. The apparent p19 mRNA half life was 3 h in irradiated and non irradiated cells. The same behavior was observed when the protein half-life was estimated in 2,5 h by pull-chase assays with S-met. Nuclear run-on experiments revealed an appreciable increase in the rate of p19 mRNA synthesis in UV treated cells in comparison with untreated ones. We measured DNA repair capacity by host cell reactivation assay. The overexpression of p19 resulted in a 80% increased repair of UV-induced DNA damage while the antisense version drove a diminished expression of DNA tested. Nevertheless, mimosine (an inhibitor of G1/S phase progression) or overexpression of p16INK4a displayed a minor effect on the rate of repair as assessed by HCR, suggesting that p19 exerts its action independently from cell cycle arrest. Regardless of p19INK4d precise mechanism the present data demonstrate that this protein is not only associated with cell cycle arrest but also with enhancement of DNA repair.INK4d induces a second photoprotective response after DNA damage. Northern blot analysis show that p19 is up-regulated after UV irradiation in BHK cells. Levels of p19INK4d mRNA peaked 12 h after UV treatment. This induction resulted dose dependent and started at 5 mJ/cm2. The apparent p19 mRNA half life was 3 h in irradiated and non irradiated cells. The same behavior was observed when the protein half-life was estimated in 2,5 h by pull-chase assays with S-met. Nuclear run-on experiments revealed an appreciable increase in the rate of p19 mRNA synthesis in UV treated cells in comparison with untreated ones. We measured DNA repair capacity by host cell reactivation assay. The overexpression of p19 resulted in a 80% increased repair of UV-induced DNA damage while the antisense version drove a diminished expression of DNA tested. Nevertheless, mimosine (an inhibitor of G1/S phase progression) or overexpression of p16INK4a displayed a minor effect on the rate of repair as assessed by HCR, suggesting that p19exerts its action independently from cell cycle arrest. Regardless of p19INK4d precise mechanism the present data demonstrate that this protein is not only associated with cell cycle arrest but also with enhancement of DNA repair.