Non-methylated islands in fish genomes are GC-poor.
In the vertebrate genomes studied to date the 5' end of many genes are associated with distinctive sequences known as CpG islands. CpG islands have three properties: they are non-methylated; the dinucleotide CpG occurs at the frequency predicted by base composition; and they are GC-rich. Unexpectedly we have found that CpG islands in certain fish only have the first two properties; that is, their GC-content is not elevated compared to bulk genomic DNA. Based on this finding, we speculate that the GC-richness of CpG islands in vertebrates other than fish is a passive consequence of a higher mutation rate in regions of open chromatin under conditions where the nucleotide precursor pools are biased.
Cross
S
S
Research Institute for Molecular Pathology, Vienna, Austria.
Kovarik
P
P
Schmidtke
J
J
Bird
A
A
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D003596:Cytosine / Q000032:analysis*; D004247:DNA / Q000032:analysis; D015226:Dinucleoside Phosphates / Q000378:metabolism; D004330:Drosophila / Q000235:genetics; D005399:Fishes / Q000235:genetics*; D006147:Guanine / Q000032:analysis*; D006801:Humans; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D008745:Methylation; D008969:Molecular Sequence Data; D051381:Rats
D000199:Actins; D003596:Cytosine; D004247:DNA; D015226:Dinucleoside Phosphates; D006147:Guanine; D008668:Metallothionein; C015772:CpG dinucleotide