Effects of PARP inhibition in mTERC+/+ and mTERC-/- MEFs on chromosome stability. (A) Acridine orange stained binucleated cell with no MN, indicating no apparent damage. (B) Acridine orange stained binucleated cell with MN from PARP inhibited mTERC-/- MEFs following 24 hour arsenite treatment. (C) Histogram of micronuclei formation, in mTERC+/+ MEFs and mTERC-/- MEFs treated with sodium arsenite [Untreated (Black columns), 1.5 μg/ml (11.5 μM) (dotted columns) and 3.0 μg/ml (23 μM) (white columns)] in the presence or absence of 3-AB. mTERC-/- MEFs displayed a greater extent of MN formation as compared to wild type MEFs at each concentration of arsenite and inhibition of PARP-1 in both MEFs further increased this difference. Frequency of chromosomal aberration such as fusion (D) and breaks (E) per cell as analysed by PNA FISH in mTERC+/+ MEFs (black columns) and in mTERC-/- MEFs (white columns) following treatment with 3-AB and/or sodium arsenite [1.5 μg/ml (11.5 μM)]. Majority of chromosomal breaks and fusions were observed in PARP inhibited mTERC-/- MEFs. Representative images of (F) fusion (arrow) and (G) breaks (arrow) from PARP inhibited mTERC-/- MEFs following 24 hour treatment with arsenite. Data is represented as mean ± SE from three independent experiments. *p < 0.05 when treated cells are compared to respective untreated controls. #p < 0.05 when 3-AB treated cells are compared to respective 3-AB untreated cells in the presence or absence of arsenite. +p < 0.05 when 3-AB treated mTERC-/- cells are compared to 3-AB treated mTERC+/+ in the absence or presence of arsenite treatment.