title: Alkylation of isolated chromatin with N-methyl-N-nitrosourea and N-ethyl-N-nitrosourea.
abstract: When isolated chromatin is incubated with the carcinogens N-methyl-N-nitrosourea (MeNU) and N-ethyl-N-nitrosourea (EtNU), DNA and chromosomal proteins become alkylated to increasingly greater extents as the carcinogen concentrations increase. With either MeNU or EtNU, the core and linker DNA of chromatin are alkylated to essentially identical extents. Alkylation of chromatin DNA as well as free DNA is drastically reduced at physiological ionic strengths (e.g. 0.15 M NaCl). The presence of 0.15 M NaCl, on the other hand, enhances alkylation of chromosomal proteins. While EtNU is much less reactive to DNA than MeNU, alkylation of chromosomal proteins relative to that of chromatin DNA has been found to be markedly greater with EtNU than with MeNU. Such a difference in their relative reactivities toward DNA and proteins may be related to the known difference of carcinogenic potency between these N-nitroso compounds.
mesh_terms: D000478:Alkylation; D000818:Animals; D002250:Carbon Radioisotopes; D002843:Chromatin / Q000187:drug effects* / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D005038:Ethylnitrosourea / Q000378:metabolism / Q000633:toxicity*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008770:Methylnitrosourea / Q000378:metabolism / Q000633:toxicity*; D009607:Nitrosourea Compounds / Q000633:toxicity*; D009994:Osmolar Concentration; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D002250:Carbon Radioisotopes; D002843:Chromatin; D009607:Nitrosourea Compounds; D008770:Methylnitrosourea; D004247:DNA; D005038:Ethylnitrosourea