The establishment of heterochromatin is an important way for cells to repress transcription. Yet not much is known about the control of heterochromatin spreading into euchromatic domains. Therefore, researchers at Duke University used the Awesome Power of Yeast (Epi)Genetics to study how specific DNA sequences affect heterochromatin spreading. Their results are published in the April 10, 2009 issue of PLoS Genetics.
To establish de novo heterochromatin domains in the S. pombe genome, the investigators inserted the L5 element, which is known to nucleate heterochromatin in fission yeast, at specific sites. Then, the extent of ectopic heterochromatin spreading and the expression levels of nearby genes were examined.
Gene sequences, independent of transcription level, antagonized heterochromatin spreading from the L5 element. In contrast, intergenic and spacer DNA sequences promoted heterochromatin spreading. These results suggest that the sequence-dependent recruitment of transcription complexes or other mediators, nucleosome positioning, and/or selective pressures could attenuate or block heterochromatin spreading. Get all the details at PLoS Genetics, April 2009.