UREA IMPROVES EFFICIENCY OF BISULFITE-MEDIATED SEQUENCING OF 5'-METHYLCYTOSINE IN GENOMIC DNA

The detection of 5'-methylcytosine by the bisulphite-mediated genomic sequencing method has considerably aided study of the role of methylat ion in areas such as X chromosome inactivation, genomic imprinting and cancer research. However on occasion difficulty has been experienced in obtaining complete conversion of cytosine to uracil in regions of t he target DNA. We report here a simple improvement to the method invol ving addition of urea to the bisulphite reaction, a step which greatly improves the reaction efficiency, presumably by maintaining the targe t DNA in single stranded form, thereby allowing complete and reliable conversion.