Genome-wide hydroxymethylation tested using the HELP-GT assay shows redistribution in cancer

S Bhattacharyya, Y Yu, M Suzuki… - Nucleic acids …, 2013 - academic.oup.com
S Bhattacharyya, Y Yu, M Suzuki, N Campbell, J Mazdo, A Vasanthakumar, TD Bhagat
Nucleic acids research, 2013academic.oup.com
hydroxymethylcytosine (5-hmC) is a recently discovered epigenetic modification that is
altered in cancers. Genome-wide assays for 5-hmC determination are needed as many of
the techniques for 5-methylcytosine (5-mC) determination, including methyl-sensitive
restriction digestion and bisulfite sequencing cannot distinguish between 5-mC and 5-hmC.
Glycosylation of 5-hmC residues by beta-glucosyl transferase (β-GT) can make CCGG
residues insensitive to digestion by MspI. Restriction digestion by HpaII, MspI or MspI after β …
Abstract
5-hydroxymethylcytosine (5-hmC) is a recently discovered epigenetic modification that is altered in cancers. Genome-wide assays for 5-hmC determination are needed as many of the techniques for 5-methylcytosine (5-mC) determination, including methyl-sensitive restriction digestion and bisulfite sequencing cannot distinguish between 5-mC and 5-hmC. Glycosylation of 5-hmC residues by beta-glucosyl transferase (β-GT) can make CCGG residues insensitive to digestion by MspI. Restriction digestion by HpaII, MspI or MspI after β-GT conversion, followed by adapter ligation, massive parallel sequencing and custom bioinformatic analysis allowed us determine distribution of 5-mC and 5-hmC at single base pair resolution at MspI restriction sites. The resulting HpaII tiny fragment Enrichment by Ligation-mediated PCR with β-GT (HELP-GT) assay identified 5-hmC loci that were validated at global level by liquid chromatography-mass spectrometry (LC-MS) and the locus-specific level by quantitative reverse transcriptase polymerase chain reaction of 5-hmC pull-down DNA. Hydroxymethylation at both promoter and intragenic locations correlated positively with gene expression. Analysis of pancreatic cancer samples revealed striking redistribution of 5-hmC sites in cancer cells and demonstrated enrichment of this modification at many oncogenic promoters such as GATA6 . The HELP-GT assay allowed global determination of 5-hmC and 5-mC from low amounts of DNA and with the use of modest sequencing resources. Redistribution of 5-hmC seen in cancer highlights the importance of determination of this modification in conjugation with conventional methylome analysis.
Oxford University Press