Buchman A R, Kornberg R D
Department of Cell Biology, Beckman Laboratories, Stanford University School of Medicine, California 94305.
Mol Cell Biol. 1990 Mar;10(3):887-97. doi: 10.1128/mcb.10.3.887-897.1990.
ABFI (ARS-binding protein I) is a yeast protein that binds specific DNA sequences associated with several autonomously replicating sequences (ARSs). ABFI also binds sequences located in promoter regions of some yeast genes, including DED1, an essential gene of unknown function that is transcribed constitutively at a high level. ABFI was purified by specific binding to the DED1 upstream activating sequence (UAS) and was found to recognize related sequences at several other promoters, at an ARS (ARS1), and at a transcriptional silencer (HMR E). All ABFI-binding sites, regardless of origin, provided weak UAS function in vivo when examined in test plasmids. UAS function was abolished by point mutations that reduced ABFI binding in vitro. Analysis of the DED1 promoter showed that two ABFI-binding sites combine synergistically with an adjacent T-rich sequence to form a strong constitutive activator. The DED1 T-rich element acted synergistically with all other ABFI-binding sites and with binding sites for other multifunctional yeast activators. An examination of the properties of sequences surrounding ARS1 left open the possibility that ABFI enhances the initiation of DNA replication at ARS1 by transcriptional activation.
ABFI（ARS结合蛋白I）是一种酵母蛋白，它能结合与多个自主复制序列（ARS）相关的特定DNA序列。ABFI还能结合位于一些酵母基因启动子区域的序列，包括DED1，DED1是一个功能未知的必需基因，其转录水平持续较高。通过与DED1上游激活序列（UAS）特异性结合纯化得到ABFI，发现它能识别其他几个启动子、一个ARS（ARS1）和一个转录沉默子（HMR E）处的相关序列。当在测试质粒中检测时，所有ABFI结合位点，无论其来源如何，在体内都提供弱UAS功能。体外降低ABFI结合的点突变消除了UAS功能。对DED1启动子的分析表明，两个ABFI结合位点与相邻的富含T的序列协同作用，形成一个强大的组成型激活剂。DED1富含T的元件与所有其他ABFI结合位点以及其他多功能酵母激活剂的结合位点协同作用。对ARS1周围序列特性的研究留下了ABFI通过转录激活增强ARS1处DNA复制起始的可能性。
