Tethered particle motion experiment investigating the histone chaperone-mediated nucleosome assembly process.

<p>(A) The schematic diagram illustrating the interaction between a 836-<i>bp</i> DNA molecule and histone in the presence of the histone chaperone, Nap1, allowing the formation of nucleosomes sequentially. The black wavy line denotes a DNA molecule anchored on a coverslip and attached to a streptavidin-labeled polystyrene bead (200 nm in diameter; drawn as a sphere) at the other. The circle denotes the histone components (H2A/H2B dimer, H3/H4 tetramer or histone octamer). The U-shaped figure denotes Nap1. The dash double-arrowed line represents the Brownian motion amplitude of tethered molecule. (B) A representative time trace for the DNA molecule in response to the addition of (i) buffer, (ii) 15 nM Nap1, (iii) 7.5 nM H2A/H2B dimer along with15 nM Nap1, (iv) 7.5 nM H3/H4 tetramer along with 15 nM Nap1, and (v) 7.5 nM histone octamer along with15nMNap1. The black line indicates the initiation of reaction. The hatched bar represents the expected BM amplitude for a 836-<i>bp</i> molecule in response to the addition of histone, which then forms the tetrasome or nucleosome. (C) The distribution of Brownian motion amplitude for the 836-<i>bp</i> DNA molecule in response to the addition of histone octamer along with Nap1 obtained from various different time traces (N = 38). Average BM amplitude of 67.9±4.4 nm, 53.5±4.3 nm, 40.1±5.3 nm, 27.3±2.4 nm and 15.0±4.6 nm, were obtained and these correspond to the status (i)–v) depicted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115007#pone.0115007.g001" target="_blank">Fig. 1(A)</a>.