Bondarenko Vladimir A, Steele Louise M, Ujvári Andrea, Gaykalova Daria A, Kulaeva Olga I, Polikanov Yury S, Luse Donal S, Studitsky Vasily M
Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane, Room 405, Piscataway, New Jersey 08854, USA.
Mol Cell. 2006 Nov 3;24(3):469-79. doi: 10.1016/j.molcel.2006.09.009.
Nucleosomes uniquely positioned on high-affinity DNA sequences present a polar barrier to transcription by human and yeast RNA polymerase II (Pol II). In one transcriptional orientation, these nucleosomes provide a strong, factor- and salt-insensitive barrier at the entry into the H3/H4 tetramer that can be recapitulated without H2A/H2B dimers. The same nucleosomes transcribed in the opposite orientation form a weaker, more diffuse barrier that is largely relieved by higher salt, TFIIS, or FACT. Barrier properties are therefore dictated by both the local nucleosome structure (influenced by the strength of the histone-DNA interactions) and the location of the high-affinity DNA region within the nucleosome. Pol II transcribes DNA sequences at the entry into the tetramer much less efficiently than the same sequences located distal to the nucleosome dyad. Thus, entry into the tetramer by Pol II facilitates further transcription, perhaps due to partial unfolding of the tetramer from DNA.
独特定位在高亲和力DNA序列上的核小体，对人类和酵母RNA聚合酶II（Pol II）的转录形成了极性障碍。在一种转录方向上，这些核小体在进入H3/H4四聚体时提供了一个强大的、对因子和盐不敏感的障碍，这种障碍在没有H2A/H2B二聚体的情况下也能重现。以相反方向转录的相同核小体形成了一个较弱、更弥散的障碍，在较高盐浓度、TFIIS或FACT作用下，这种障碍在很大程度上得以缓解。因此，障碍特性由局部核小体结构（受组蛋白-DNA相互作用强度影响）和核小体内高亲和力DNA区域的位置共同决定。Pol II转录进入四聚体处的DNA序列的效率远低于位于核小体二分体远端的相同序列。因此，Pol II进入四聚体促进了进一步的转录，这可能是由于四聚体与DNA发生了部分解折叠。
