Methylation patterns in the isochores of vertebrate genomes

5-Methylcytosine (5mC) levels were determined in compositional DNA fractions corresponding to different isochore families from the genomes of Xenopus, chicken, mouse and human, four vertebrates which show different isochore patterns. The results obtained indicate that: (i) positive correlations exis...

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Bibliographic Details
Published in:Gene 1997-12, Vol.205 (1), p.119-124
Main Authors: Cacciò, Simone, Jabbari, Kamel, Matassi, Giorgio, Guermonprez, Fanny, Desgrès, Jean, Bernardi, Giorgio
Format: Article
Language:English
Subjects:
5-methylcytosine
Animals
chickens
CpG dinucleotides
CpG Islands - genetics
cpg ratio
cytosine
DNA Methylation
Genome
Humans
mice
nucleotide sequences
species differences
Vertebrate evolution
Vertebrates - genetics
Xenopus laevis
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Summary:5-Methylcytosine (5mC) levels were determined in compositional DNA fractions corresponding to different isochore families from the genomes of Xenopus, chicken, mouse and human, four vertebrates which show different isochore patterns. The results obtained indicate that: (i) positive correlations exist between the 5mC levels and the GC levels of isochores within any given genome; and (ii) DNA from Xenopus isochore families is twice as methylated as DNA from the isochores having the same GC levels from mouse, human and chicken. Moreover, the positive correlations holding between CpG levels and the GC 3 levels of coding sequences of warm-blooded vertebrates were shown to comprise two regions with a border at approx. 75% GC 3. The correlation corresponding to the higher region (which comprises only very rare high GC 3 values in the case of Xenopus) has a higher slope than that corresponding to the lower GC 3 values, a phenomenon due in all likelihood, to the increasing contribution of CpG islands. Finally, the observed/expected CpG ratio is higher in Xenopus than in warm-blooded vertebrates.
ISSN:0378-1119
1879-0038
DOI:10.1016/S0378-1119(97)00560-X