Histone methylation and DNA methylation: a missed pas de deux in invertebrates?

Several Authors have reported that histone methylation interacts with DNA methylation creating a self-propagating epigenetic cycle for long-term transcriptional repression of methylated genome compartments. This phenomenon, observed in plant and vertebrate genomes, does not appear to hold true in invertebrates. In particular, both structural and functional evidences suggest that, in invertebrates, DNA methylation and histone methylation do not interact, thus inhibiting the intimate pas de deux observed in other eukaryotes.