PerspectiveMolecular Biology

A New Direction for Gene Loops

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Science  02 Nov 2012:
Vol. 338, Issue 6107, pp. 624-625
DOI: 10.1126/science.1230576

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The textbook illustration of a gene depicts a linear structure, with flanking regulatory sequences—a promoter on the left and a terminator on the right, to start and stop transcription, respectively. However, recent analyses of chromatin architecture have revealed that the promoter and terminator elements are not necessarily separate in three-dimensional space, but can be juxtaposed to form “gene loops” (1, 2). Gene loops are not static structures; they form transiently in a transcription-dependent manner. But what function do they serve? On page 671 of this issue, Tan-Wong et al. report that gene loops restrict divergent transcription from inherently bidirectional promoters, repressing the synthesis of noncoding RNA (3).