Published in Zeitschrift für Naturforschung C
Different ways for studying DNA synthesis and DNA methylation were investigated. On the one hand the reactions were measured by incorporation of several specific precursors, taking into ac count that pool alterations might influence the results. The best way to avoid this is the direct conversion of DNA cytosine to DNA 5-methyl-cytosine by using [...
Published in Proceedings of the National Academy of Sciences of the United States of America
A cytosine-specific DNA methylase activity, which is normally absent in the Escherichia coli B strain, was found to be induced in these cells by infection with bacteriophage varphiX174. In vivo experiments revealed a single 5-methylcytosine residue in the phage DNA molecule and 5-methylcytosine residues in the infected host DNA, in addition to the ...
Published in Proceedings of the National Academy of Sciences of the United States of America
Methyl groups placed on varphiXsB1 replicative form DNA by the Escherichia coli B modification enzyme are located in the overlap between fragments Mbo II-3 and Alu I-2, a 61-base-pair DNA segment. Mutations that led to loss of susceptibility to restriction by E. coli B occurred within this segment at three positions spanning 14 nucleotides. A seque...
Published in BBA Section Nucleic Acids And Protein Synthesis
Cells of the mosquito Aedes albopictus have 5.6 pg DNA cell. This DNA is 58 mol% (A + T) and has about 0.03 mol% each of 5-methylcytosine and 6-methylaminopurine. The DNA is largely degraded by the restriction enzyme HpaII showing the virtual absence of the sequence CMeCGG. Small amounts of enzymic activity recovered largely in non-nuclear fraction...
Published in BBA Section Nucleic Acids And Protein Synthesis
After injecting rats with di[ 14C]methylnitrosamine we have prepared liver chromatin and have examined firstly, the methylation level of the DNAase I-degradable fraction of the DNA and secondly, the level of methylation and the stability of methylated sites in chromatin RNA. Our results show that the level of 7-methylguanine in the degradable DNA i...
Published in BBA Section Nucleic Acids And Protein Synthesis
O 6-Methyldeoxyguanosine and O 6-ethyldeoxyguanosine are weak inhibitors (of approximately equal potency) of the removal of O 6-methylguanine from methylated DNA by a rat liver enzyme in vitro. When administered to rats, O 6-ethyldeoxyguanosine retarded the removal from liver DNA of the O 6-methylguanine which had been produced by pretreatment with...
Published in BBA Section Nucleic Acids And Protein Synthesis
A specific class of DNA sequences, the inverted repetitive sequences, forms a double-stranded structure within a single linear polynucleotide chain in denatured DNA. The reassociation process is unimolecular and occurs very fast. Quantitative analyses have shown that in mouse P815 cells these sequences comprise about 4% of the nuclear DNA and are i...
Published in BBA Section Nucleic Acids And Protein Synthesis
Mitochondrial DNAs from yeast, Neurospora, rat and calf do not contain internally methylated cytosine in -CCGG- sequences.
Published in BBA Section Nucleic Acids And Protein Synthesis
An improved method of purification of DNA methylase from Krebs II ascites cells is reported. The enzyme sediments at 8.3 S on glycerol-gradients and a major band on SDS polyacrylamide gel electrophoresis has a molecular weight of 184 000. Aggregation occurs at low salt and this may interfere with enzymic activity. The preferred double stranded DNA ...
Published in Proceedings of the National Academy of Sciences of the United States of America
Methylation patterns of Chlamydomonas chloroplast DNAs (chlDNAs) were examined in the vegetative, gametic, and zygotic stages of the life cycle. Restriction endo-nuclease fragment patterns produced by EcoRI, BamHI, Hpa II, and Msp I were compared; the last two cleave DNA at the sequence C-C-G-G, but Hpa II is blocked by prior methylation of the int...
