ROLE OF NUCLEOSOMAL CORES AND HISTONE-H1 IN REGULATION OF TRANSCRIPTION BY RNA POLYMERASE-II
ROLE OF NUCLEOSOMAL CORES AND HISTONE-H1 IN REGULATION OF TRANSCRIPTION BY RNA POLYMERASE-II
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DOI：
10.1126/science.1718039
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发表时间：
1991-10-11
期刊：
影响因子：
56.9
通讯作者：
KADONAGA, JT
中科院分区：
文献类型：
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作者：
LAYBOURN, PJ;KADONAGA, JT
染色质结构和转录活性之间的关系进行了检查，在体外转录分析的染色质重建组蛋白H1的存在或不存在。为了保持明确的模板DNA，纯化的组分用于染色质的重建。核小体核心的平均密度为每200个DNA碱基对1个核小体的重建导致基础RNA聚合酶II转录的轻微减少，为裸DNA模板获得的25%至50%。这种核小体介导的抑制是由于位于RNA起始位点的核小体核心，并且不能被序列特异性转录激活因子Sp1和GAL 4-VP 16抵消。当H1以每个核小体0.5 ~ 1.0个分子（200个碱基对的DNA）掺入染色质时，RNA合成减少到仅含核小体核心的染色质所观察到的1%~ 4%，并且这种H1介导的抑制可以通过添加Sp1或GAL 4-VP 16（抗抑制）来抵消。对于裸DNA模板，Sp1和GAL 4-VP-16分别使转录增加3倍和8倍（真激活）。然而，在H1抑制的染色质模板中，Sp1和GAL 4-VP 16介导的转录激活的幅度分别高出90倍和200倍以上，这是因为真实激活和抗抑制的综合作用。这些数据提供了直接的生化证据，支持和澄清先前提出的模型，其中有耗尽或重组的核小体核心和组蛋白H1的启动子区的活性基因。
The relation between chromatin structure and transcriptional activity was examined by in vitro transcription analysis of chromatin reconstituted in the absence or presence of histone H1. To maintain well-defined template DNA, purified components were used in the reconstitution of chromatin. Reconstitution of nucleosomal cores to an average density of 1 nucleosome per 200 base pairs of DNA resulted in a mild reduction of basal RNA polymerase II transcription to 25 to 50 percent of that obtained with naked DNA templates. This nucleosome-mediated repression was due to nucleosomal cores located at the RNA start site and could not be counteracted by the sequence-specific transcription activators Sp1 and GAL4-VP16. When H1 was incorporated into the chromatin at 0.5 to 1.0 molecule per nucleosome (200 base pairs of DNA), RNA synthesis was reduced to 1 to 4 percent of that observed with chromatin containing only nucleosomal cores, and this H1-mediated repression could be counteracted by the addition of Sp1 or GAL4-VP16 (antirepression). With naked DNA templates, transcription was increased by a factor of 3 and 8 by Sp1 and GAL4-VP-16, respectively (true activation). With H1-repressed chromatin templates, however, the magnitude of transcriptional activation mediated by Sp1 and GAL4-VP16 was 90 and more than 200 times higher, respectively, because of the combined effects of true activation and antirepression. The data provide direct biochemical evidence that support and clarify previously proposed models in which there is depletion or reconfiguration of nucleosomal cores and histone H1 at the promoter regions of active genes.