ISSN:
0730-2312
Keywords:
rDNA
;
lymphoblastoid
;
methylation
;
hypermethylation
;
DNA
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
In human lymphoplastoid cell line (Z83) in which rDNA genes on chromosomes 22 are amplified but transcribed at a low level, immunocytological studies with antibodies to 5 methylcytidine provided evidence for hypermethylation of the rDNA. The extent of methylation of the 5′ flanking sequence of the ribosomal DNA was examined by comapring the size of restriciton fragments obtained by digestion of genomic DNA with EcoRI and Hpall or EcoRI and Mpsl. Southern blots indicated hypermethylation of the 5′ flanking sequences of many copies of rRNA genes in these cells, but not in a control lymphoblastoid cell line without rDNA amplification. Results obtained with somatic hybird human-hamster cell line, in which the rRNA genes on the single human chromosomes 22 are inactive, showed that only a small fraction of the CCGG sites in the 5′ flanking sequences of the transcriptionally silent rRNA genes in this hybird were methylated. Since inactive rRNA genes can show such a minimal level of methylation, it is likely that the extreme hypermethylation of the apmlified rRNA genes in Z83 association with their inactivation rather than following it. © 1992 Wiley-Liss, Inc.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcb.240500404
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