Partners in imprinting: noncoding RNA and polycomb group proteins.

Establishment of genomic imprints during early development involves concerted epigenetic mechanisms. Two recent studies by Terranova et al. (in this issue of Developmental Cell) and Pandey et al. (in a recent issue of Molecular Cell) have demonstrated that Polycomb group proteins (PcG) and the Kcnq1ot1 regulatory RNA, respectively, are indispensable for gene- and lineage-specific chromatin modification and compaction of the paternally imprinted Kcnq1 cluster.