We have earlier reported that alkylation of DNA by the chemical carcinogen dimethyl sulphate, which mainly alkylates N-7 of guanine and N-3 of adenine, causes the formation of partially denatured regions in double-stranded DNA (Rizvi RY, Alvi NK & Hadi SM, Biosci. Rep.2, 315–322, 1982). It is known that the major site of alkylation in DNA by N-ethyl-N-nitrosourea (EtNu) are the phosphate groups. N-methyl-N-nitrosourea (MeNu), on the other hand, causes the alkylation of mainly guanine residues. We have therefore studied the effect of these two alkylating carcinogens on the secondary structure of DNA. DNA aikylated with increasing concentrations of EtNu and MeNu was subjected to alkaline and S1 nuclease hydrolysis. Thermal melting profiles of alkylated DNA were also determined using S1 nuclease. The results indicated that alkylation by the two alkylating agents had a differential effect on the secondary structure of DNA. EtNu-alkylated DNA was found to be more thermostable than native DNA at neutral pH. It was however more alkali-labile than MeNu-alkylated DNA. The greater stability of EtNu-alkylated DNA was considered to be due to abolition of negative charges on phosphate alkylation.
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September 01 1984
Effect of alkylation with N-methyl-N-nitrosourea and N-ethyl-N-nitrosourea on the secondary structure of DNA
R. Y. Rizvi;
R. Y. Rizvi
1Biochemistry Division, Chemistry Department, Aligarh Muslim University, Aligarh-202001, India
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S. M. Hadi
S. M. Hadi
1Biochemistry Division, Chemistry Department, Aligarh Muslim University, Aligarh-202001, India
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Publisher: Portland Press Ltd
Received:
July 25 1984
Online ISSN: 1573-4935
Print ISSN: 0144-8463
© 1984 The Biochemical Society
1984
Biosci Rep (1984) 4 (9): 729–735.
Article history
Received:
July 25 1984
Citation
R. Y. Rizvi, S. M. Hadi; Effect of alkylation with N-methyl-N-nitrosourea and N-ethyl-N-nitrosourea on the secondary structure of DNA. Biosci Rep 1 September 1984; 4 (9): 729–735. doi: https://doi.org/10.1007/BF01128813
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