Cell cycle inhibitor, p19INK4d, is up-regulated in cellular senescence triggered by camptothecin

SONZOGNI S.; VIDELA RICHARDSON G.; OGARA M.F.; CÁNEPA, E.T.; SCASSA, M. E.

Mar del Plata

Congreso; XLIII REUNION ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACION EN BIOQUIMICA Y BIOLOGIA MOLECULAR (SAIB); 2007

SOCIEDAD ARGENTINA DE INVESTIGACION EN BIOQUIMICA Y BIOLOGIA MOLECULAR (SAIB)

Cellular senescence is a state of stable cell cycle arrest triggered by stress strimuli. Disruption of DNA damage response prevents senescence and promotes transformation. Given the function of cyclin dependent kinase inhibitor, p19INK4d, in cell cycle arrest and DNA repair, the aim of this work is to elucidate if this protein is involved in this process. Senescence was induced with camptothecin. Treated cells exhibit characteristic of senescence such as flat and enlarged morphology, increase beta-galactosidase activity, cell cycle arrest and upregulation of p16INK4a and p21Cip1. Northern blot analyses show that p19 is uperegulated after camptothecin treatment in BHK cells. Levels of p19 peak at 12 h after camptothecin addition. This induction is dose dependent and starts at 20 nM. Reporter gene experiments with a construct harboring 2250 bp of p19 promoter indicate that camptothecin is acting at the transcriptional level. Abrogation of ATM kinase activity severely impairs genotoxic action. Transient expression assays with a mutagenized promoter construct reveal that up-regulation of transcription requires E2F. A significant increase in the percentage of cells undergoing senescence is observed in BHK stably overexpressing p19 when compared to wild type or p19 deficient counterparts. Our results suggest that p19 may influence the induction of senescence triggered by camptothecin.