title: Tissue- and expression level-specific chromatin looping at maize b1 epialleles.
abstract: 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.
authors.affiliation: Swammerdam Institute for Life Sciences, Universiteit van Amsterdam, 1098 XH Amsterdam, The Netherlands.
authors.forename: Marieke
authors.initials: M
authors.lastname: Louwers
authors.forename: Rechien
authors.initials: R
authors.lastname: Bader
authors.forename: Max
authors.initials: M
authors.lastname: Haring
authors.forename: Roel
authors.initials: R
authors.lastname: van Driel
authors.forename: Wouter
authors.initials: W
authors.lastname: de Laat
authors.forename: Maike
authors.initials: M
authors.lastname: Stam