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Plant Cell. 2009 Mar;21(3):832-42. doi: 10.1105/tpc.108.064329. Epub 2009 Mar 31.

Tissue- and expression level-specific chromatin looping at maize b1 epialleles.

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  • 1Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, 1098 XH Amsterdam, The Netherlands.


This work examines the involvement of chromatin looping in the transcriptional regulation of two epialleles of the maize (Zea mays) b1 gene, B-I and B'. These two epialleles are tissue-specifically regulated and are involved in paramutation. B-I and B' are expressed at high and low levels, respectively. A hepta-repeat approximately 100 kb upstream of the transcription start site (TSS) is required for both paramutation and high b1 expression. Using chromosome conformation capture, we show that the hepta-repeat physically interacts with the TSS region in a tissue- and expression level-specific manner. Multiple repeats are required to stabilize this interaction. High b1 expression is mediated by a multiloop structure; besides the hepta-repeat, other sequence regions physically interact with the TSS as well, and these interactions are epiallele- and expression level-specific. Formaldehyde-assisted isolation of regulatory elements uncovered multiple interacting regions as potentially regulatory.

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