Polycomb-group proteins
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Polycomb-group proteins are a family of proteins first discovered in fruit flies that can remodel chromatin such that transcription factors cannot bind to promoter sequences in DNA. Polycomb group proteins play a role in silencing HOX genes through modulation of chromatin structure.[1]
In insects
In Drosophila, the Trithorax-group (trxG) and Polycomb-group (PcG) proteins act antagonistically and interact with chromosomal elements, termed Cellular Memory Modules (CMMs). Trithorax-group (trxG) proteins maintain the active state of gene expression while the Polycomb-group (PcG) proteins counteract this activation with a repressive function that is stable over many cell generations and can only be overcome by germline differentiation processes. Polycomb Gene complexes or PcG silencing involves at least three kinds of multiprotein complex PRC1, PRC2 and PhoRC which work together to carry out their repressive effect.
In mammals
In humans Polycomb Group gene expression is important in many aspects of development. Although pathogenic mutations in polycomb group genes have not been identified, abnormal levels of PcG proteins correlate with the severity and invasiveness of several cancer types. The mammalian PRC1 core complexes are very similar to Drosophila.
References
- ↑ Portoso M and Cavalli G (2008). "The Role of RNAi and Noncoding RNAs in Polycomb Mediated Control of Gene Expression and Genomic Programming". RNA and the Regulation of Gene Expression: A Hidden Layer of Complexity. Caister Academic Press. ISBN 978-1-904455-25-7.
- 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)
- Drosophila Genes in Development: Polycomb-group in the Homeobox Genes DataBase
- polycomb group proteins on humpath.com
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.
- polycomb+group+proteins at the US National Library of Medicine Medical Subject Headings (MeSH)