Inactive X chromosome has the highest concentration of unmethylated Hha I sites.
A procedure enabling the highly sensitive detection of accessible restriction endonuclease sites on metaphase chromosomes is described. The procedure is based on the following: (i) a terminal deoxynucleotidyltransferase is used to add a biotinylated nucleotide (Bio-11-dUTP) tail to the 3' hydroxyl terminus generated by the action of a restriction enzyme and (ii) the biotinylated oligonucleotide is detected by a peroxidase-based immunocytochemical method. When used with the 5-methylcytosine-sensitive enzyme Hha I, it gives rise to a pattern close to R and T banding on autosomes. In addition, the staining of one X chromosome in females appears very unusual by its pattern and its strong intensity. This procedure, as applied on a case with a polysomy X chromosome, provides direct evidence of an overall hypomethylation of the inactive X chromosomes.
Viegas-Pequignot
E
E
Centre National de la Recherche Scientifique Unité Associée 620, Institut Curie, Paris, France.
Dutrillaux
B
B
Thomas
G
G
D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts; D006801:Humans; D007150:Immunohistochemistry; D008214:Lymphocytes; D008297:Male; D008677:Metaphase; D008745:Methylation; D014960:X Chromosome
D004247:DNA; D015252:Deoxyribonucleases, Type II Site-Specific; C037130:GCGC-specific type II deoxyribonucleases