Linking Stochastic Fluctuations in Chromatin Structure and Gene Expression
Figure 2
EM analysis of single gene molecules.
(A) PHO5 gene chromatin rings were formed by site-specific recombination in vivo [14]. Isolated chromatin rings were crosslinked with psoralen, denatured, and analyzed by EM. Positions of UASp1, UASp2, and the TATA box are indicated by a black, gray, and white circles, respectively; gray ovals represent nucleosomes; promoter nucleosomes are in light gray; RS refers to the recognition sequence for site-specific recombination; and lexA refers to a cluster of LexA operators for ring purification. (B) EM images of transcriptionally inactive PHO5 rings (pho4Δ pho80Δ). (C) EM images of transcriptionally active PHO5 rings (PHO4 pho80Δ). Black arrowheads indicate nucleosome-free DNA segments long enough to accommodate one or more nucleosomes. Bars denote 100 nm.