Molecular Biology

Activation from Within

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Science  15 Jan 2010:
Vol. 327, Issue 5963, pp. 251
DOI: 10.1126/science.327.5963.251-e

The protein complexes that wrap DNA come in two flavors: core histones and variant histones. Although the H2A histone variant MacroH2A1 is known for its role in repressing transcription in the context of X chromosome inactivation, Gamble et al. describe an activating effect of this factor on autosomal gene expression. They have used chromatin immunioprecipitation and genomic tiling arrays (ChIP-chip) to map the distribution of MacroH2A1 in human primary fibroblasts and a breast cancer cell. MacroH2A1 associates with large chromatin domains (greater than 500 kb) with boundaries near transcription start sites; when MacroH2A1 sits within a transcribed region, repression is often the result, but some genes, such as those involved in responding to serum starvation, are instead protected from silencing.

Genes Dev. 24, 21 (2010).

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