The inactive X chromosome in the human female is enriched in 5-methylcytosine to an unusual degree and appears to contain more of this modified nucleotide than the remainder of the genome.
By employing a procedure that combines ELISA and photoacoustic spectroscopy, we have examined the content of 5-methylcytosine (m(5)C) in DNA of individuals who differed from one another in the number of X chromosomes in their genomes. The results show that the human inactive X chromosome (Xi) contains very high amounts of this modified nucleotide. We estimate that in the 46,XX female there is more m(5)C in Xi (~ 3.6 x 10(7)) than in all the remaining chromosomes put together (~ 2.1 x 10(7)). Our results also suggest that nearly one-fifth of all cytosines in Xi are methylated and that, in addition to CpG methylation, there is extensive non-CpG methylation as well.
Deobagkar
Deepti D
DD
Department of Zoology, University of Pune, Pune 411 007, India. dddeo@unipune.ernet.in
Chandra
H Sharat
HS
D044503:5-Methylcytosine / Q000378:metabolism*; D041321:Chromosomes, Human, X; D018899:CpG Islands; D004247:DNA / Q000378:metabolism*; D019175:DNA Methylation; D018900:Dinucleotide Repeats; D005260:Female; D005333:Fetus / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D015894:Genome, Human; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism
D044503:5-Methylcytosine; D004247:DNA