MECHANISM OF TRANSCRIPTIONAL ANTIREPRESSION BY GAL4-VP16
MECHANISM OF TRANSCRIPTIONAL ANTIREPRESSION BY GAL4-VP16
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DOI：
10.1101/gad.6.12a.2270
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发表时间：
1992-12-01
影响因子：
10.5
通讯作者：
KADONAGA, JT
中科院分区：
文献类型：
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作者：
CROSTON, GE;LAYBOURN, PJ;KADONAGA, JT
启动子和增强子结合因子似乎通过促进转录反应以及抵消染色质介导的抑制（抗抑制）而起作用。我们研究了混合激活剂GAL4-VP16的机制，通过使用H1-DNA复合物和重组含有h1的染色质模板，GAL4-VP16能够抵消组蛋白h1介导的抑制。GAL4 DNA结合区域本身足以破坏局部H1-DNA相互作用，但转录激活区域对于抗抑制是额外必要的。gal4 - vp16介导的抗抑制需要一种辅助因子，称为共抗抑制因子，该因子部分从果蝇胚胎中纯化。我们发现共抗抑制因子的活性对RNA酶a的消化很敏感，而且，来自果蝇胚胎的总RNA可以部分替代共抗抑制因子部分，这表明共抗抑制因子可能作为组蛋白受体（“组蛋白库”）发挥作用。这些发现提示了一种基因激活模型，其中序列特异性转录因子在启动子处破坏H1-DNA相互作用，促进H1转移到组蛋白受体，然后允许基础转录因子进入DNA模板。
Promoter- and enhancer-binding factors appear to function by facilitating the transcription reaction as well as by counteracting chromatin-mediated repression (antirepression). We have examined the mechanism by which a hybrid activator, GAL4-VP16, is able to counteract histone H1-mediated repression by using both H1-DNA complexes and reconstituted H1-containing chromatin templates. The GAL4 DNA binding domain alone was sufficient to disrupt local H1-DNA interactions, but a transcriptional activation region was additionally necessary for antirepression. GAL4-VP16-mediated antirepression required an auxiliary factor, denoted as a co-antirepressor, which was partially purified from Drosophila embryos. We have found that the co-antirepressor activity was sensitive to digestion with RNase A. Moreover, total RNA from Drosophila embryos could partially substitute for the co-antirepressor fraction, which indicated that the co-antirepressor may function as a histone acceptor ("histone sink"). These findings suggest a model for gene activation in which sequence-specific transcription factors disrupt H1-DNA interactions at the promoter to facilitate transfer of H1 to a histone acceptor, which then allows access of the basal transcription factors to the DNA template.