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Mol Cell Biol. 2005 May;25(10):3864-74.

The human beta-globin locus control region can silence as well as activate gene expression.

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Division of Hematology, Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.


Using recombinase-mediated cassette exchange to test multiple transgenes at the same site of integration, we demonstrate a novel chromatin context-dependent silencer activity of the beta-globin locus control region (LCR). This silencer activity requires DNase I hypersensitive sites HS2 and HS3 but not HS4. After silencing, the silenced cassettes adopt a typical closed chromatin conformation (histone H3 and H4 deacetylation, histone H3-K4 methylation, DNA methylation, and replication in late S phase). In the absence of the LCR at the same site of integration, the chromatin remains decondensed. We demonstrate that the LCR is necessary but not sufficient to trigger these chromatin changes. We also provide evidence that this novel silencing activity is caused by transcriptional interference triggered by activation of transcription in the flanking sequences by the LCR.

[Indexed for MEDLINE]
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