DNA methylation in normal and tumour virus-transformed cells in tissue culture. I. The level of DNA methylation in BHK21 cells and in BHK21 cells transformed by polyoma virus (PyY cells).

Abstract The proportion of the cytosine moieties in DNA which are methylated to 5-methylcytosine at the macromolecular level has been determined in BHK21 cells and compared with the proportion of this minor base in the DNA of polyoma virustransformed BHK21 cells under identical conditions. Almost twice as much 5-methylcytosine was detected in the DNA of the PyY cells as was present in the BHK21 cells, both quantities being calculated relative to the total cytosine in the DNA of the relevant cell line. The possibility that 5-methylcytosine could also arise from the amination of thymine within the DNA was investigated. No evidence for the operation of this pathway was detected within the experimental limits, which would have detected 0.2 % amination of the thymine of either cell line. When the cells were grown at lower densities the proportion of 5-methylcytosine in the DNA of both cell lines was increased, but the difference between the levels in each cell line was maintained. The possibility that the level of 5-methylcytosine in DNA in mammalian cells could alter with their rate of DNA synthesis, or their degree of contact inhibition, was investigated by synchronising the cells with deoxyadenosine. Different levels of methylation were observed in both cell lines at different rates of DNA synthesis.

[1]  R. Burdon.  Methylation of Nucleic Acids in Krebs II Ascites Tumour Cells , 1966, Nature.

[2]  E. Chargaff,et al.  Studies on the nucleotide arrangement in deoxyribonucleic acids. IV. Patterns of nucleotide sequence in the deoxyribonucleic acid of rye germ and its fractions. , 1960, Biochimica et biophysica acta.

[3]  E. Chargaff,et al.  The composition of the pentose nucleic acids of yeast and pancreas. , 1948, The Journal of biological chemistry.

[4]  A. Newton,et al.  A simple paper chromatographic method for separation of methylated adenines and cytosine from the major bases found in nucleic acids. , 1971, Analytical biochemistry.

[5]  P. R. Srinivasan,et al.  Deoxyribonucleic acid methylase of mammalian tissues. , 1968, Biochemistry.

[6]  N. Morris,et al.  Deoxyribonucleic acid methylase activity in rat spleen. , 1968, The Journal of biological chemistry.

[7]  I. Macpherson,et al.  Polyoma transformation of hamster cell clones--an investigation of genetic factors affecting cell competence. , 1962, Virology.

[8]  H. Eagle,et al.  Amino acid metabolism in mammalian cell cultures. , 1959, Science.

[9]  H. Bond,et al.  Density-Gradient centrifugation of DNA in a fixed-angle rotor: A higher order of resolution , 1966 .

[10]  G. R. Wyatt.  The purine and pyrimidine composition of deoxypentose nucleic acids. , 1951, The Biochemical journal.

[11]  G. Marin,et al.  Reversion in Polyoma-transformed Cells: Retransformation, Induced Antigens and Tumorigenicity , 1969, Journal of virology.

[12]  B. Vanyushin,et al.  Rare Bases in Animal DNA , 1970, Nature.

[13]  R. Burdon,et al.  Enzymic modification of chromosomal macromolecules. II. The formation of histone epsilon-N-trimethyl-L-lysine by a soluble chromatin methylase. , 1971, Biochimica et biophysica acta.

[14]  R. Burdon.  Enzymic modification of chromosomal macromolecules. I. DNA and protein methylation in mouse tumour cell chromatin. , 1971, Biochimica et biophysica acta.

[15]  M. Stoker.  Characteristics of normal and transformed clones arising from BHK21 cells exposed to polyoma virus. , 1962, Virology.

[16]  B. Sanwal,et al.  MODERN METHODS OF PLANT ANALYSIS , 1955 .

[17]  N. Xeros.  Deoxyriboside Control and Synchronization of Mitosis , 1962, Nature.

[18]  J. Smith,et al.  Polynucleotides from Deoxyribonucleic Acids , 1952, Nature.

[19]  L. Crawford,et al.  THE NUCLEIC ACID OF SIMIAN VIRUS 40. , 1964, Virology.

[20]  B. Vanyushin,et al.  DNA‐methylase in loach embryos (Misgurnus fossilis) , 1971, FEBS letters.

[21]  E. Chargaff,et al.  Nucleic Acids , 2020, Definitions.

[22]  R. Burdon,et al.  The in vivo methylation of DNA in mouse fibroblasts. , 1969, Biochimica et biophysica acta.

[23]  E. Winocour,et al.  On the 5-methylcytosine found in the DNA extracted from polyoma virus☆ , 1967 .