UNWINDING OF NUCLEOSOMAL DNA BY A DNA HELICASE
UNWINDING OF NUCLEOSOMAL DNA BY A DNA HELICASE
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DOI：
10.1074/jbc.270.5.2024
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发表时间：
1995-02-03
影响因子：
4.8
通讯作者：
KOWALCZYKOWSKI, SC
中科院分区：
文献类型：
--
作者：
EGGLESTON, AK;ONEILL, TE;KOWALCZYKOWSKI, SC
我们已经询问了DNA解旋酶是否可以解旋包含在分离的天然染色质和重组染色质中的DNA，所述重组染色质包含在线性串联重复序列上的规则间隔的核小体核心阵列。我们发现大肠杆菌recBCD酶能够解旋这些DNA底物并置换核小体，尽管随着模板上核小体密度的增加，酶解旋的速率和持续合成能力都受到抑制（最大分别为3倍和>25倍）。如果组蛋白八聚体是化学交联的，则观察到的解旋速率不受影响;从HeLa细胞核分离的天然染色质的解旋在接头组蛋白H1存在和不存在的情况下都发生。这些结果表明，当解旋酶解旋DNA时，它们通常通过清除DNA中的组蛋白或DNA结合蛋白来促进核过程。
We have asked whether a DNA helicase can unwind DNA contained within both isolated native chromatin and reconstituted chromatin containing regularly spaced arrays of nucleosome cores on a linear tandem repeat sequence, We find that Escherichia coli recBCD enzyme is capable of unwinding these DNA substrates and displacing the nucleosomes, although both the rate and the processivity of enzymatic unwinding are inhibited (a maximum of 3- and >25-fold, respectively) as the nucleosome density on the template is increased. The observed rate of unwinding is not affected if the histone octamer is chemically cross-linked; thus, dissociation, or splitting, of the histone octamer is not required for unwinding to occur, The unwinding of native chromatin isolated from HeLa cell nuclei occurs both in the absence and in the presence of linker histone H1, These results suggest that as helicases unwind DNA, they facilitate nuclear processes by acting to clear DNA of histones or DNA-binding proteins in general.