The restriction enzyme EheI (GGC/GCC) is sensitive to CpG methylation.

Ehel cleaves the site GGC/GCC and is an isoschizomer of Narl (GG/CGCQ and Bbel (GGCGC/C) (1 -4) . Here I show that Ehel is methyl sensitive and will not cleave its CpG methylated site (GC^CGCC). Narl and Bbel are also CpG methyl sensitive (5—7). Ehel methyl sensitivity is shown by digesting mixtures of methylated X DNA and unmethylated plasmid DNA and viceversa (Figure 1). I also digest eukaryotic DNAs with Ehel. Figure 1 shows a digest of Physarum rDNA (which has published methylation patterns, ref. 6) and a digest of adenovinis DNA (which is unmethylated and is a standard substrate for Narl, ref. 8). Ehel readily cleaves its unmethylated sites, including those in X and pBR322 (1, 2 and this paper). Bbel is slow and Narl very slow to cleave some unmethylated sites including the one in X DNA (5, 8 and my unpublished results). Ehel readily cleaves its unmethylated sites and does not cleave GCHZGCC sites. Ehel should be very reliable for long range restriction mapping and methylation pattern mapping of eukaryotic genomes.