Human DNA methyltransferase 3a does not associate with microRNAs in the regulation of DNA methylation

Despite important roles in mammalian gene regulation, the critical targeting mechanism of DNA methylation for specific DNA sequences remains unclear. Recently, small non-coding RNAs were reported to be essential for DNA methylation in plants as well as in mice, suggesting that small non-coding RNAs might interact with DNA methyltransferases (DNMTs) to provide them with target sequence information. In the present study, we attempted to detect and isolate microRNAs by immunoprecipitation (IP) that might be associated with human DNMT3a. When analyzed by gel electrophoresis after radioisotope-labeling, DNMT3a IP revealed no detectable levels of microRNA. RNA from DNMT3a IP was also analyzed with microRNA microarray and with subsequent RT-PCR. The results showed no specific enrichment of candidate microRNAs in the DNMT3a IP. DNMT3a was not directly associated with microRNAs. But, other classes of small non-coding RNA could still be implicated with DNMTs in a specific tissue such as testis where such RNA species are highly abundant.