Cell fate decisions can be maintained during long periods of developmental time by stable states of gene expression. The Polycomb group and trithorax group proteins of Drosophila are key transcriptional regulators that maintain stable expression states during development. Recent advances in knowledge about individual Polycomb group and trithorax group proteins, their mechanisms of action, and potential homologs in mice and humans are contributing to a greater understanding of their roles in gene expression and development.
Bibliographical noteFunding Information:
1 thank Rick Jones, Mike O'Connor, Welcome Bender, Anne Chiang, Ann Rougvie and Tom Hays for discussions and comments on the manuscript. 1 also thank Welcome Bender, Martha Soto, Hugh Brock, Peter Harte and Markus Noll for providing information prior to publication. I apologize to colleagues in the field since, due to space limitations, it was sometimes necessary to cite review articles rather than the primary literature. Also the effort to provide the most recent references to each PcG gene resulted in a lack of direct citations to the original discoveries of some of these genes; \[31,78\] and references therein should be consulted for this information. This work was supported by NSF grant IBN-9304936 and a University of Minnesota McKnight Land-Grant Professorship.