A comparative study on the effect of tumor promoters on poly ADP-ribosylation in A431 cells.
Poly ADP-ribosylation is a post-translational modification of chromatin proteins catalyzed by the enzyme poly-ADPR transferase (poly-ADPRT) and affects the structure as well as the functional properties of chromatin. It is of particular relevance in carcinogenesis, as it represents an epigenetic mechanism for modulation of gene expression. In the present study, A431 cells were exposed to tumor promoters phorbol-12-myristate-13-acetate (PMA), benzoyl peroxide (BP), mezerein and 6-keto-lithocholic acid (KA), and their effect on poly-ADP-ribosylation was studied. All these tumor promoters increased the activity of poly-ADPRT in these cells--PMA 2.3-fold, BP and mezerein 2.2-fold each and KA 1.3-fold. The enzyme inhibitor 3-amino benzamide (3AB) partially prevented the stimulation of poly-ADPRT by these promoters. There was a concomitant decrease in NAD levels, the substrate for poly-ADPRT. The decrease was 44% for PMA, 46% for BP, 21% for KA and 34% for mezerein. The induction of poly-ADP-ribose synthesis by PMA and BP appears to be mediated at least in part by active oxygen species, as they induced an increase in superoxide anions and anti-oxidants prevented the increase of poly-ADPRT activity to varying extents.
Singh
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Department of Biochemistry, All India Institute of Medical Sciences, New Delhi.
D001549:Benzamides / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002273:Carcinogens / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy*; D004247:DNA / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D066298:In Vitro Techniques; D009243:NAD / Q000032:analysis; D011064:Poly Adenosine Diphosphate Ribose / Q000096:biosynthesis*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000096:biosynthesis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001549:Benzamides; D002273:Carcinogens; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D009243:NAD; D011064:Poly Adenosine Diphosphate Ribose; C025160:3-aminobenzamide; D004247:DNA; D011065:Poly(ADP-ribose) Polymerases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium