EVIDENCE FOR ADENINE METHYLATION WITHIN THE MOUSE MYOGENIC GENE MYO-D1

Previous studies have indicated that there may be uncleavable TaqI sit es (TCGA) within the mouse myogenic gene, Myo-D1, Fragments of DNA bea ring most of the presumed insensitive TaqI sites have been reproduced using PCR. The presence of each of the originally uncleavable TaqI sit es has been confirmed and each TaqI site has been shown to be sensitiv e to TaqI hydrolysis in PCR-synthesised genomic DNA. Since TaqI is inh ibited by methylation of the adenine residue within its recognition se quence (but not by cytosine methylation), it is suggested that specifi c adenine bases are methylated in the coding region of Myo-DI and main tained throughout cell division. The same TaqI recognition sequences a re insensitive to digestion in genomic DNA isolated from various mouse tissues including fetus, regenerating skeletal muscle and a myogenic cell line, all of which express Myo-D1. Thus, adenine methylation is n ot a modification of DNA following gametic fusion nor does it appear t o play a major role in regulation of Myo-D1 expression.