Patent ID: 7985550

Claim:
A method for isolating methylated CpG islands comprising the steps of (a) digesting eukaryotic genomic DNA with a first restriction endonuclease which recognizes a recognition sequence found in A/T rich regions of DNA or found in CpG island-poor regions of DNA; (b) digesting the eukaryotic genomic DNA with a second restriction endonuclease which recognizes a 4 base-pair sequence in unmethylated C/G rich regions; (c) isolating DNA fragments of at least 1 kb formed by the steps of digesting and inserting the fragments into bacterial vectors; (d) transforming non-methylating, non-restricting bacteria with the bacterial vectors to propagate the vectors and render the fragments' progeny unmethylated; (e) digesting the unmethylated fragments with a third restriction endonuclease which recognizes a sequence of at least 6 base pair in G/C rich regions; and (f) isolating the resulting fragments and inserting said fragments into bacterial vectors to form a library of sequences which are enriched for sequences derived from methylated CpG islands in the eukaryotic genome.