Effects of tween 60 on benzo(a)pyrene uptake by Tetrahymena pyriformis and by isolated rat liver mitochondria

Nucleotide incorporation by human DNA polymerase gamma opposite benzo[a]pyrene and benzo[c]phenanthrene diol epoxide adducts of deoxyguanosine and deoxyadenosine

Mitochondria are major cellular targets of benzo[a]pyrene (BaP), a known carcinogen that also inhibits mitochondrial proliferation. Here, we report for the first time the effect of site-specific N2-deoxyguanosine (dG) and N6-deoxyadenosine (dA) adducts derived from BaP 7,8-diol 9,10-epoxide (BaP DE) and dA adducts from benzo[c]phenanthrene 3,4-diol 1,2-epoxide (BcPh DE) on DNA replication by exonuclease-deficient human mitochondrial DNA polymerase (pol gamma) with and without the p55 processivity subunit. The catalytic subunit alone primarily misincorporated dAMP and dGMP opposite the BaP DE-dG adducts, and incorporated the correct dTMP as well as the incorrect dAMP opposite the DE-dA adducts derived from both BaP and BcPh. In the presence of p55 the polymerase incorporated all four nucleotides and catalyzed limited translesion synthesis past BaP DE-dG adducts but not past BaP or BcPh DE-dA adducts. Thus, all these adducts cause erroneous purine incorporation and significant blockage of further primer elongation. Purine misincorporation by pol gamma opposite the BaP DE-dG adducts resembles that observed with the Y family pol eta. Blockage of translesion synthesis by these DE adducts is consistent with known BaP inhibition of mitochondrial (mt)DNA synthesis and suggests that continued exposure to BaP reduces mtDNA copy number, increasing the opportunity for repopulation with pre-existing mutant mtDNA and a resultant risk of mitochondrial genetic diseases.

Photodynamic action of thiopyronine on the respiration and fermentation in yeast

The efficiency of photodynamic treatment with thiopyronine (TP) on the respiration and fermentation of yeast cells, on the metabolic oxygen uptake of isolated mitochondrial preparations from yeast, and on the enzyme activity of alcohol dehydrogenase (ADH) in vivo and in vitro were studied. Respiration was inactivated by treatment with TP and visible light more at the initial stage than was the fermentation. Isolated mitochondria and ADH in vitro were not as sensitive to treatment as were respiration and fermentation in vivo. Inactivation patterns of respiration and fermentation in vivo showed that the inactivation was not due to damage to the DNA. The hindrance of respiration and fermentation might be one of main causes of cell-death resulting from photodynamic treatment.