Spreading the silence: epigenetic transcriptional regulation during Drosophila development.

In early Drosophila development a complex cascade of diffusible transcription factors generates an intricate expression pattern of developmental regulators such as the homeotic genes. The mechanism which subsequently maintains the pattern during the rest of development is mainly using epigenetic features for its function. Evidence comes from the analysis of the Polycomb-group (Pc-G), a class of genes which is responsible for maintaining the inactive state of expression.