The mealybug chromosome system I: Unusual methylated bases and dinucleotides in DNA of aPlanococcus species |
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Authors: | Dileep N Deobagkar K Muralidharan Sushilkumar G Devare Krishna K Kalghatgi H Sharat Chandra |
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Institution: | (1) Microbiology and Cell Biology Laboratory ICMR Centre for Genetics and Cell Biology, Indian Institute of Science, 560 012 Bangalore;(2) Laboratory of Cellular and Molecular Biology, National Cancer Institute, NIH, 20205, MD, USA;(3) Department of Chemical Engineering, Yale University, 06520 New Haven, CT, USA |
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Abstract: | The methylation status of the nuclear DNA from a mealybug, aPlanococcus species, has been studied. Analysis of this DNA by High Performance Liquid Chromatography and Thin Layer Chromatography revealed
the presence of significant amounts of 5-—methylcytosine. Since analysis of DNA methylation using the Msp I/Hpa II system
showed only minor differences in susceptibility of the DNA to the two enzymes, it seemed possible that 5-methylcytosine (5mC)
occurred adjacent to other nucleotides in addition to its usual position, next to guanosine. This was verified by dinucleotide
analysis of DNA labelledin vitro by nick translation. These data show that the total amount of 5-methylcytosine in this DNA is slightly over 2.3 mol %, of
which 0.61% occurs as the dinucleotide 5mCpG, 0.68% as 5mCpA, 0.59% as 5mCpT and 0.45% as 5mCpC. 5mCpG represents approximately
3.3% of all CpG dinucleotides. The experimental procedure would not have permitted the detection of 5mCp5mC, if it occurs
in this system. Unusually high amounts of 6-methyladenine (approximately 4 mol %) and 7-methylguanine (approximately 2 mol
%) were also detected, 6-methyladenine and 7-methylguanine occurred adjacent to all four nucleotides. The total G+C content
was 33.7% as calculated from dinucleotide data and 32.9% as determined from melting profiles. |
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Keywords: | Mealybug (Planococcus) chromosome imprinting chromosome inactivation diffuse centromere DNA methylation 7-methylguanine |
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