ABSTRACT
It has been proposed that considerable DNA damage may be caused by endogenous metabolites produced during the body's normal metabolic processes. Several metabolites including L-3,4-dihydroxyphenylalanine and dopamine have been previously shown to lead to oxidative DNA breakage in the presence of copper ions. 5-hydroxytryptamine or serotonin is an important neurotransmitter in brain and spinal cord and is involved in the control of sleep and consciousness, aggression and mood. In this paper we show that serotonin is also capable of causing strand cleavage in DNA in the presence of Cu(II) through an oxidative mechanism. Serotonin reduces Cu(II) to Cu(I) which is accompanied by the generation of hydroxyl radical. Spectroscopic data indicate that serotonin is able to bind to DNA and copper ions. Relative DNA cleavage efficiency and copper binding ability of serotonin and structurally related molecules tryptophan and melatonin indicates that the phenolic group in serotonin is required for strand cleavage activity.
Subject(s)
Central Nervous System/metabolism , Copper/metabolism , DNA Damage/physiology , DNA/metabolism , Hydroxyl Radical/metabolism , Oxidative Stress/physiology , Serotonin/metabolism , Animals , Cattle , Copper/pharmacology , DNA/drug effects , Melatonin/metabolism , Melatonin/pharmacology , Oxidation-Reduction , Plasmids/drug effects , Plasmids/genetics , Plasmids/metabolism , Serotonin/pharmacology , Single-Strand Specific DNA and RNA Endonucleases/drug effects , Single-Strand Specific DNA and RNA Endonucleases/metabolism , Thymus Gland/drug effects , Thymus Gland/metabolism , Tryptophan/metabolism , Tryptophan/pharmacologyABSTRACT
The capacity of promoter DNA of two yeast genes to be unwound was studied. Both promoters, those of the CYC1 and DED1 genes, contain long oligopurine.oligopyrimidine (R.Y) tracts. The two promoters were cloned into negatively supercoiled plasmids, and their sensitivity to single-strand specific nuclease P1 was examined. Extensive P1 cleavage was located within the R.Y tracts, and cleavage sites were mapped. The extent of cleavage was only slightly dependent on P1 concentration, indicating a slow conversion of an intermediate form of DNA into the P1 reactive state. The cleavage required negative supercoiling and was suppressed by NaCl, MgCl2 and spermine. Two-dimensional topoisomer analysis showed that six superhelical turns were opened in the plasmids examined. The results indicate that at sufficient torsional stress, the R.Y tracts can intermittently undergo a transition into an unwound, ready-to-separate state. The oligopurine.oligopyrimidine tracts may thus serve as DNA unwinding centers in the gene promoters where they reside.
