Nicotine mediates hypochlorous acid-induced nuclear protein damage in mammalian cells.

Activated neutrophils secrete hypochlorous acid (HOCl) into the extracellular space of inflamed tissues. Because of short diffusion distance in biological fluids, HOCl-damaging effect is restricted to the extracellular compartment. The current study aimed at investigating the ability of nicotine, a component of tobacco and electronic cigarettes, to mediate HOCl-induced intracellular damage.

Amino acid chloramine damage to proliferating cell nuclear antigen in mammalian cells.

Unlabelled: Amino acid chloramines (AACLs) are reactive secondary products of activated neutrophils. To understand AACL damage in cell nuclei, we exploited proliferating cell nuclear antigen (PCNA) as a nuclear protein damage reporter, using western blotting and mass spectrometry. Chloramines of proline, arginine, and glycine caused significant damage to PCNA in cells.

Nuclear targets of photodynamic tridentate ruthenium complexes.

Octahedral ruthenium complexes, capable of photodynamic singlet oxygen production at near 100% efficiency, were shown to cause light-dependent covalent crosslinking of p53 and PCNA subunits in mammalian cells and cell lysates. Azide, a singlet oxygen quencher, greatly reduced the p53 photocrosslinking, consistent with the idea that singlet oxygen is the reactive oxygen species involved in p53 photocrosslinking. A photodynamically inactive ruthenium complex, [Ru(tpy)(2)](2+) (tpy = [2,2';6',2'']-terpyridine), had no effect on p53 or PCNA photocrosslinking.

Ubiquitin-family modifications of topoisomerase I in camptothecin-treated human breast cancer cells.

Camptothecins kill mammalian cells by stabilizing topoisomerase I-DNA strand passing intermediates that are converted to lethal double strand DNA breaks in DNA replication fork collisions. Camptothecin-stabilized topoisomerase I-DNA cleavage intermediates in mammalian cells are uniquely modified by ubiquitin-family proteins. The structure, composition, and function of these ubiquitin-family modifications are poorly understood.

PCNA damage caused by antineoplastic drugs.

Structurally diverse chemotherapeutic and chemopreventive drugs, including camptothecin, doxorubicin, sanguinarine, and others, were found to cause covalent crosslinking of proliferating cell nuclear antigen (PCNA) trimers in mammalian cells exposed to fluorescent light. This PCNA damage was caused by both nuclear and cytoplasmically localizing drugs. For some drugs, the PCNA crosslinking was evident even with very brief exposures to laboratory room lighting.

Deubiquitination by proteasome is coordinated with substrate translocation for proteolysis in vivo.

The 26S proteasome mediates degradation of protein substrates labeled with polyUb chains. After recognition by the 19S proteasome regulatory complex, polyUb chains are disassembled and substrates are processed in the 20S core of proteasome. However, the exact relationship of degradation-associated deubiquitination to substrate processing remains unclear.

DNA sequence specificity for topoisomerase II poisoning by the quinoxaline anticancer drugs XK469 and CQS.

The two known antineoplastic quinoxaline topoisomerase II poisons, XK469 (NSC 697887) and CQS (chloroquinoxaline sulfonamide, NSC 339004), were compared for DNA cleavage site specificity, using purified human topoisomerase IIalpha and human topoisomerase IIbeta. The DNA cleavage intensity pattern for topoisomerase IIalpha poisoning by CQS closely resembled that of VM-26, despite the lack of any apparent common pharmacophore. In contrast, the topoisomerase IIalpha DNA cleavage intensity patterns of XK469 and CQS were very different from one another despite the similar overall structures of the two drugs.