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Protosilencers as building blocks for heterochromatin
Author(s) -
Fourel Geneviève,
Lebrun Eléonore,
Gilson Eric
Publication year - 2002
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/bies.10139
Subject(s) - heterochromatin , biology , heterochromatin protein 1 , gene silencing , genetics , budding yeast , saccharomyces cerevisiae , telomere , dna , microbiology and biotechnology , yeast , gene , chromatin
DNA repetitions may provoke heterochromatinization. We explore here a model in which multiple cis ‐acting sequences that display no silencing activity on their own (protosilencers) may cooperate to establish and maintain a heterochromatin domain efficiently. Protosilencers, first defined in budding yeast, have now been found in a wide range of genomes where they appear to stabilize and to extend the propagation of heterochromatin domains. Strikingly, isolated or moderately repeated protosilencers can also be found in promoters where they participate in transcriptional activation and have insulation functions. This suggests that the proper juxtaposition of a threshold number of protosilencers converts them from neutral or transactivating elements into ones that nucleate heterochromatin. Interactions might be transient or permanent, and are likely to occur over distances by looping. This model provides a conceptual framework for as varied phenomena as telomere‐driven silencing in Drosophila , X inactivation in mammals, and rDNA silencing in S. cerevisiae . It may also account for the silencing that occurs when multiple copies of a transgene are inserted in tandem. BioEssays 24:828–835, 2002. © 2002 Wiley Periodicals, Inc.