Imprinted small RNA genes.

Genomic imprinting is an epigenetic phenomenon that results in differential expression of both alleles, depending on their parent of origin. We have recently identified many imprinted small noncoding RNA genes belonging to the C/D RNA and microRNA gene families, both of which are usually known to play key roles in posttranscriptional metabolism of specific genes (e.g. C/D RNAs guide ribose methylation of target RNAs while microRNAs elicit either translational repression or RNA interference). Although the functional and evolutionary significance of this association between C/D RNA genes, microRNA genes and genomic imprinting is still highly elusive, these observations provide a framework for further analysis of the potential role of small noncoding RNAs in epigenetic control.