ING1b tumor suppressor requires functional checkpoint kinase 1 to exert its DNA repair activity

CERUTI, J. M.; OGARA M.F.; PALMERO, I.; CANEPA E.T.

Potrero de los Funes, San Luis, República Argentina

Congreso; XLVII REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN EN BIOQUÍMICA Y BIOLOGÍA MOLECULAR (SAIB); 2011

SOCIEDAD ARGENTINA DE INVESTIGACIÓN EN BIOQUÍMICA Y BIOLOGÍA MOLECULAR (SAIB)

Inhibitor of Growth 1b (ING1b), a member of the ING proteinfamily, is involved in senescence, cell cycle arrest, apoptosis andDNA repair. Here, we studied the role of endogenous ING1b inDNA repair, in wild type and Ing1 deficient g/g MEFs, treated withH2O2 or neocarzinostatin (NCS) as genotoxic agents. In absence of ING1 DNA repair is impaired in unscheduled DNA synthesis (UDS)assays for both treatments. Moreover, transfection of Ing1bantisense oligonucleotide in wt MEFs reduced DNA repair to levelsin g/g MEFs. g/g MEFs showed higher levels of gH2AX, a markerof DSBs, relative to wt MEFs. These displayed a slower kinetics ofgH2AX appearance than g/g MEFs indicating that ING1bdeficiency results in an exacerbated response to DNA damage. Weshowed that ING1b transcript and protein are up-regulated by H2O2,NCS and UV in MEFs, HCT116 and H1299 cells and this inductionis independent of p53. We also detected ING1b phosphorylation inHCT116 cells by metabolic labelling after DNA damage,independently of p53. Moreover, ING1b DNA repair activity in wtMEFs is completely abolished when Chk1 is inhibited bySB218078. In summary, ING1b improves DNA repair in responseto a variety of genotoxic agents. We propose that physiologicallevels of ING1b are required to trigger a proper DNA damageresponse. Finally, phosphorylation of ING1b, probably by Chk1 isnecessary to exert its DNA repair activity.