Evidence for nonrandom behavior in 208-12 subsaturated nucleosomal array populations analyzed by AFM.
Evidence for nonrandom behavior in 208-12 subsaturated nucleosomal array populations analyzed by AFM.
复制标题
通过 AFM 分析 208-12 亚饱和核小体阵列群体中非随机行为的证据。
作者：
Yodh,JG;Lyubchenko,YL;Shlyakhtenko,LS;Woodbury,N;Lohr,D
原子力显微镜用于确定重建的亚饱和208-12核小体阵列中的种群分布。这些分布的特征随每个模板分子核小体的平均装载量（nav）而变化：当nav< 4时，分布呈现单峰，其宽度与随机装载过程的预期宽度相等；Atnav = 4 ~ 8时，分布比随机分布更宽，且较复杂；也就是说，它们包含多个峰值和/或肩部。此外，峰/肩通常出现在两个核小体间隔，即2,4,6或3,5,7核小体。这种双核小体的周期性在统计上是显著的。分布中这种离散特征的确切原因尚不清楚，但至少这些特征似乎表明在这些负荷水平下核小体占据的一些成对偏好。在这些中间水平（nav= 4−8）分布中，主峰包含的总模板比随机核小体装载过程所产生的模板的比例更大。这一特征表明，在这些中间群体水平上，模板之间存在一些相关核小体装载的趋势。与非乙酰化的核小体阵列相比，高乙酰化的核小体阵列在种群分布上仅显示出细微的差异，并证明了上述特征。原子力显微镜允许人们研究不固定的染色质阵列；我们发现208-12模板上的核小体在没有戊二醛固定时表现出显著的不稳定性。
Atomic force microscopy was used to determine the population distributions in reconstituted, subsaturated 208-12 nucleosomal arrays. The features found in these distributions vary with the average nucleosome loading per template molecule (nav): atnav< 4, the distributions show a single peak whose breadth is equal to that expected for a random loading process; atnav= 4−8, the distributions are broader than random distributions and are complex; i.e., they contain multiple peaks and/or shoulders. Moreover, the peaks/shoulders typically occur at two nucleosome intervals, i.e., 2, 4, 6 or 3, 5, 7 nucleosomes. This two-nucleosome periodicity is statistically significant. The precise cause for such discrete features within the distributions is unknown, but at least these features would seem to indicate some pairwise preference in nucleosome occupation at these loading levels. In these intermediate-level (nav= 4−8) distributions, the major peak contains a larger fraction of the total templates than a random nucleosome loading process would produce. This feature indicates that at these intermediate population levels there is some tendency for correlated nucleosome loading among the templates. Hyperacetylated nucleosomal arrays show only subtle differences in their population distributions compared to nonacetylated arrays and demonstrate the above features. AFM allows one to study unfixed chromatin arrays; we find that nucleosomes on the 208-12 template demonstrate significant lability when they are not glutaraldehyde-fixed.