MODULATION OF (+ -)-ANTI-BPDE MEDIATED P53 ACCUMULATION BY INHIBITORSOF PROTEIN-KINASE-C AND POLY(ADP-RIBOSE) POLYMERASE/

The rapid accumulation of the p53 gene product is considered to be an important component of the cellular response to a variety of genotoxin s, In order to gain insights on the biochemical pathways leading to p5 3 stabilization, the effect of (+/-) 7,8-dihydroxy-anti-9, 10-epoxy-7, 8,9,10-tetrahydrobenzo(a)-pyrene [(+/-)-anti-BPDE] induced DNA damage on p53 protein levels was investigated in various repair-proficient an d repair-deficient human cells, Brief exposure of normal human fibrobl asts to 0.05-1 mu M (+/-)-anti-BPDE resulted in elevated p53 protein l evels as compared to the constitutive levels of control sells, The rap id induction response, detectable within a few hours, was sustained up to a period of at least 24 h, Repair-proficient and repair-deficient (XPA) human lymphoblastoid cells showed a similar response, The poly(A DP-ribose) polymerase inhibitor, 3-aminobenzamide (3-AB), diminished t he p53 induction response by concomitantly decreasing the extent of (/-)-anti-BPDE induced DNA damage in cells pretreated with the inhibito r, However, the direct involvement of poly ADP-ribosylation was also a pparent as 3-AB was able to attenuate (similar to 50%) the p53 respons e by post-damage inhibitor treatment of the cells, Inhibition:of cellu lar DNA replication by hydroxyurea and AraC, in the presence or absenc e of DNA damage, also resulted in rapid p53 accumulation in repair-def icient cells, On the contrary, inhibition of protein kinase C (PKC) by calphostin-C led to an abrogation of (+/-)-anti-BPDE mediated p53 ind uction, Analysis of the downstream effects of carcinogen treatment sho wed that the lymphoblastoid cells undergo DNA fragmentation indicative of apoptosis while fibroblasts exhibit cell cycle arrest at the G(1)- S boundary.