IDENTIFICATION OF ESTROGEN-MODIFIED NUCLEOSIDES FROM CALF THYMUS DNA REACTED WITH 6-HYDROXYESTROGEN 6-SULFATES

Two estrogen sulfates, pyridinium 3-methoxyestra-1,3,5(10)-trien-6 alp ha-yl sulfate (3MeE-6 alpha-S) and its GP-isomer (3MeE-6 beta-S), synt hesized as model compounds to demonstrate the carcinogenesis of estrog en, were found to react with calf thymus DNA to produce steroid-modifi ed DNA adducts. Digestion of the DNA by nuclease P1 and phosphodiester ase I followed by alkaline phosphatase gave a deoxyribonucleoside frac tion, of which N-2-[3-methoxyestra-1,3,5( 10)-trien-6 alpha-yl]deoxygu anosine, N-2-[3-methoxyestra-1,3,5( 10)-trien-6 beta-yl]deoxyguanosine , N-6-[3-methoxyestra-1,3,5(10)-trien-6 alpha-yl]deoxyadenosine, and N -6-[3-methoxyestra-1,3,5(10)trien-6 alpha-yl]deoxyadenosine (identifie d as a base adduct) were identified using HPLC by comparing them with authentic specimens prepared by reacting dG; and dA with both sulfates . No steroid-dC adduct was detected in the digestion products of the D NA adduct, although dC reacted with the sulfates to form N-4-[3-methox yestra-1,3,5(10)-trien-G beta-yl] deoxycytidine, These results mean th at estrogen B-sulfate has an ability to modify DNA via the amino group of a guanine or adenine residue in DNA. The present studies imply tha t a sequential metabolism (hydroxylation and sulfation) at the Cs-posi tion of the estrogen molecule causes damage to DNA.