Trithorax-group proteins
Trithorax-group proteins are chromatin regulatory proteins which generally act to maintain gene expression. This group of proteins is rather heterogeneous and contains members that form several multiprotein chromatin complexes. One main activity of the Trithorax complex is to activate transcription by inducing trimethylation of lysine 4 of histone H3 at specific regulatory sites in their target chromatin. This active state is reinforced by acetylation of histone H4. In addition, some Trithorax-group proteins have chromating remodeling activity, using the energy of ATP to mobilize nucleosomes.
Polycomb-group proteins are the repressive couterpart to the Trithorax group proteins in that they also bind to the chromatin at the Hox genes and act to induce trimethylation of lysine 4 of histone H3, to prevent acetylation at histone H4, and to counteract nuclesome remodeling, thus maintaning silent states of gene expression.
References
- Chromatin organization and the Polycomb and Trithorax groups in The Interactive Fly
- Polycomb silencing mechanisms and the management of genomic programmes - Y. B. Schwartz, V. Pirrotta (Jan 2007); Nat. Rev. Genet. 8(1):9 (PMID 17173055)
- Genome Regulation by Polycomb and Trithorax Proteins. Schuettengruber, B., Chourrout, D., Vervoort, M., Leblanc, B., and Cavalli, G. (2007). Cell 128, 735-745 (PMID 17320510)
External links
- The Polycomb and Trithorax page of the Cavalli lab This page contains useful information on Polycomb and trithorax proteins, in the form of an introduction, links to published reviews, list of Polycomb and trithorax proteins, illustrative power point slides and a link to a genome browser showing the genome-wide distribution of these proteins in Drosophila melanogaster.