ING1B TUMOR SUPPRESSOR REQUIRES FUNCTIONAL

CERUTI, JM; OGARA, MF; PALMERO, IGNACIO; CÁNEPA E T

Congreso; XLVII SAIB; 2011

SAIB

ING1B TUMOR SUPPRESSOR REQUIRES FUNCTIONAL CHECKPOINT KINASE 1 TO EXERT ITS DNA REPAIR ACTIVITY Ceruti JM1, Ogara MF1, Palmero I2, Cánepa ET1. 1Depto. Química Biológica, FCEN, UBA, Argentina. 2Instituto Investigaciones Biomédicas, UAM, España. E-mail: julce@qb.fcen.uba.ar Inhibitor of Growth 1b (ING1b), a member of the ING protein family, is involved in senescence, cell cycle arrest, apoptosis and DNA repair. Here, we studied the role of endogenous ING1b in DNA repair, in wild type and Ing1 deficient g/g MEFs, treated with H O or neocarzinostatin (NCS) as genotoxic agents. In absence of 2 2 ING1 DNA repair is impaired in assays for both treatments. Moreover, transfection of Ing1b antisense oligonucleotide in wt MEFs reduced DNA repair to levels in g/g MEFs. g/g MEFs showed higher levels of gH2AX, a marker of DSBs, relative to wt MEFs. These displayed a slower kinetics of gH2AX appearance than g/g MEFs indicating that ING1b deficiency results in an exacerbated response to DNA damage. We showed that ING1b transcript and protein are up-regulated by H O , 2 2 NCS and UV in MEFs, HCT116 and H1299 cells and this induction is independent of p53. We also detected ING1b phosphorylation in HCT116 cells by metabolic labelling after DNA damage, independently of p53. Moreover, ING1b DNA repair activity in wt MEFs is completely abolished when Chk1 is inhibited by SB218078. In summary, ING1b improves DNA repair in response to a variety of genotoxic agents. We propose that physiological levels of ING1b are required to trigger a proper DNA damage response. Finally, phosphorylation of ING1b, probably by Chk1 is necessary to exert its DNA repair activity.