Formation of triple-stranded DNA at d(GA center dot TC)(n) sequences prevents nucleosome assembly and is hindered by nucleosomes
Formation of triple-stranded DNA at d(GA center dot TC)(n) sequences prevents nucleosome assembly and is hindered by nucleosomes
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DOI：
10.1074/jbc.271.50.31807
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发表时间：
1996-12-13
影响因子：
4.8
通讯作者：
Azorin, F
中科院分区：
文献类型：
--
作者：
Espinas, ML;JimenezGarcia, E;Azorin, F
简单重复d(GA.DNA序列经常在真核启动子中发现，在某些情况下，它们在体内被证明是无核小体的。这些序列表现出高度的结构多态，并能够采用几种类型的非B-DNA构象，在这里，我们表明这些序列的结构多样性影响它们被装入核小体的能力。核小体组装到携带d(GA.TC)(N)不同长度的序列(n=10和n=22)是非常有效的，然而，当简单的重复序列形成[CT(GA.TC)]三倍体，核小体组装要么被阻止，就像在d(GA.TC)(22)序列，或导致三链构象失稳，如d(GA.TC)(10)序列，类似地，当序列被组织成核小体时，三链DNA的形成被阻碍。只有在相对较高的离子强度(0.6M氯化钠)下，当核小体部分失稳并导致核小体颗粒破坏时，才能有效地形成三倍体DNA。这些结果表明，核小体组装和三倍体形成是相互竞争的过程。
Simple repeating d(GA . TC)(n) DNA sequences are frequently found at eukaryotic promoters, and in some cases they have been shown to be nucleosome free in vivo. These sequences show a high degree of structural polymorphism and are capable of adopting several types of non-B-DNA conformations, Here we show that the structural versatility of these sequences affects their ability to be packed into nucleosomes. Nucleosome assembly onto short double-stranded DNA fragments carrying d(GA . TC)(n) sequences of different length (n = 10 and n = 22) is very efficient, However, when the simple repeating sequence is forming a [CT(GA . TC)] tripler, nucleosome assembly is either prevented, as in the case of the d(GA . TC)(22) sequence, or results in the destabilization of the triple-stranded conformation, as in the case of the d(GA . TC)(10) sequence, Similarly, formation of triple-stranded DNA is hindered when the sequence is organized as nucleosomes. Efficient formation of tripler DNA occurs only at relatively high ionic strength (0.6 M NaCl), when the nucleosome is partially destabilized, and results in the disruption of the nucleosomal particle, These results indicate that nucleosome assembly and tripler formation are competing processes.