title: Effects of 3-aminobenzamide on cellular ribosomal RNA content and cell cycle progression in inhibitor resistant and sensitive L1210 cells.
abstract: The poly(ADP-ribosyl)ation inhibitor 3 aminobenzamide (3AB) is used extensively to probe the involvement of post-translational modifications of proteins in the control of DNA repair and cell cycle progression. However, 3AB appears to lack specificity for the synthetase, and the use of excessive concentrations of the inhibitor may adversely affect the potential responsiveness of cells to DNA-damaging agents. Here we address the concentration dependency of the cellular impact of 3AB alone by using flow cytometry to analyze the cell cycle phase-dependent, anti-proliferative effects of 3AB on mouse L1210 cells together with fluctuations in RNA (predominantly ribosomal) levels. We report that 3AB, at cytostatic concentrations, does not block cells in G2 committed to mitosis but imposes an immediate G1 and S phase arrest. Eventually cells arrested in G1 and S phase can reenter cycle but become irreversibly blocked in G2 and are incapable either of progression to mitosis or of the reinitiation of DNA synthesis when cytokinesis is blocked by colcemid exposure. 3AB exposure rapidly reduced RNA levels in all phases of the cell cycle with recovery from depletion apparent only at nontoxic concentrations (5 mM). The responses of a 3AB-resistant subline, capable of sustained culture growth in a normally cytostatic concentration of inhibitor (25 mM), suggest a close association between the sensitivity to RNA depletion and cell cycle arrest.
authors.affiliation: MRC Clinical Oncology and Radiotherapeutics Unit, MRC Centre, Cambridge, United Kingdom.
authors.forename: P J
authors.initials: PJ
authors.lastname: Smith
authors.forename: J V
authors.initials: JV
authors.lastname: Watson
authors.forename: S
authors.initials: S
authors.lastname: Shall
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism; D004351:Drug Resistance; D007700:Kinetics; D007939:Leukemia L1210 / Q000378:metabolism / Q000473:pathology; D051379:Mice; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D012334:RNA, Neoplasm / Q000187:drug effects / Q000378:metabolism; D012335:RNA, Ribosomal / Q000187:drug effects / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism
chemical_list: D001549:Benzamides; D004273:DNA, Neoplasm; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D012334:RNA, Neoplasm; D012335:RNA, Ribosomal; C025160:3-aminobenzamide