核小体
质粒
PBR322电话
组蛋白
组蛋白八聚体
螺线管
碱基对
DNA
生物
连接器DNA
染色质
遗传学
分子生物学
物理
量子力学
作者
Shinwu Jeong,James D. Lauderdale,Arnold Stein
标识
DOI:10.1016/0022-2836(91)90597-y
摘要
We have found that histone H5 (or H1) induces physiological nucleosome spacings and extensive ordering on some plasmid constructions, but not on others, in a fully defined in vitro system. Plasmid pBR327 containing DNA insertions with lengths close to 300 basepairs permitted histone H5 to induce a remarkable degree of nucleosome alignment. Seventeen multiples of a unit 210(±4) base-pair repeat, covering the entire plasmid, were detected. Plasmid pBR327, not containing a DNA insert, permitted continuous alignment of only a few nucleosomes. These observations suggest that a necessary requirement in this system for histone H5 (or H1) -induced nucleosome alignment on small (<4 kb; 1 kb = 103 bases or base-pairs) circular plasmids may be that the total DNA length must be close to an integer multiple of the nucleosome repeat length generated, a type of boundary effect. Consistent with this hypothesis, five deletion constructs of pBR327 (not containing inserts), that spanned 64% of the plasmid, and possessed DNA lengths close to integer multiples of 210 base-pairs, permitted nucleosome alignment by histone H5. We have also found that plasmid length adjustment is not a sufficient condition for nucleosome alignment. For example, plasmids pBR322 and pUC18 did not permit nucleosome alignment when adjusted to near-integer multiples of 210 base-pairs. Also, for pBR327 that contained a length-adjusted deletion in one particular region, appreciable nucleosome alignment no longer occurred. These data suggest that a contiguous approximately 800 base-pair region of pBR327, interrupted in pBR322 and not present in pUC18, can nucleate histone H5-induced nucleosome alignment, which can then spread to adjacent chromatin. Supporting this idea, a positioned five-nucleosome array appears to originate in the required region. Additionally, on a larger (6·9 kb) plasmid construction, the “chromatin organizing region” of pBR327 and adjacent DNA on one side of it exhibited preferred H5-induced nucleosome alignment.
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