Preliminary study on structure and chemical characteristics of deoxyguanoside-benzoquinone adducts / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To detect the structure and chemical characteristics of the adduct from the reaction of p-benzoquinone (BQ) with deoxyguanoside (dGMP).</p><p><b>METHODS</b>dGMP and calf thymus DNA were reacted with BQ in buffered solutions with neutral pH, the reaction products were separated and purified by high performance liquid chromatograph (HPLC), and then characterized by UV spectroscopy and mass spectrometry.</p><p><b>RESULTS</b>The reaction of BQ with dGMP yielded two adduct products (Ad(1) and Ad(2) respectively). The characterized results of Ad(1) suggested that BQ reacted at the N-1 and N(2) position of dGMP by losing one H(2)O molecule, the molecular weight of Ad(1) was 437, and the molecular formula was C(16)H(16)O(8)N(5)P. Ad(1) could also be detected from calf thymus DNA reacted with BQ in vitro, which possessed the same elution profile by HPLC analysis. Meanwhile, Ad(2) was detected in the experimental condition. It was proposed that Ad(2) was formed by BQ reacted at the N-9 position of dGMP by losing one molecule of deoxyribose, the molecular weight was 241, and the molecular formula was C(11)H(7)O(2)N(5).</p><p><b>CONCLUSION</b>The structure of one major adduct from reaction of BQ with DNA is (3'-OH)-1, N(2)-C(6)H(5)CH-2'-deoxyguanosine-5'-monophosphate.</p>

In vitro and in vivo inhibition of telomerase activity from Chinese hamster V79 cells.

While studying the inhibition of telomerase activity in Chinese hamster V79 cells using polymerase chain reaction (PCR) based telomeric repeat amplification protocol (TRAP) assay, we had earlier observed that 7-deaza deoxy guanosine triphosphate (7-deaza dGTP) and oligonucleotide (TTAGGG)4 inhibited telomerase activity in vitro. In the present study, we report inhibition of telomerase activity by modified base 7-deaza deoxy adenosine triphosphate (7-deaza dATP) and phosphorothioate TTAGGG (PS-TTAGGG). Both the compounds inhibited telomerase activity in a concentration dependent manner; 8.5 microM of 7-deaza dATP and 0.1 microM of PS-TTAGGG being the concentration for 50% of the maximum inhibition. This observation supports our earlier hypothesis that incorporation of a modified nucleotide into telomere possibly interferes with the recognition of the telomerase and TTAGGG interferes with the RNA component of telomerase. We have further shown that treatment of cells with nicotinamide (NA) and benzamide (BA), well known inhibitors of poly (ADP-ribose) polymerase, reduced telomerase activity. We speculate that modification of the telomeric binding proteins or other components by poly (ADP-ribosyl)ation may be involved in such inhibition.