Motta M C, Caretti G, Badaracco G F, Mantovani R
Dipartimento di Genetica e Biologia dei Microrganismi, Università di Milano, Via Celoria 26, 20133 Milano, Italy.
J Biol Chem. 1999 Jan 15;274(3):1326-33. doi: 10.1074/jbc.274.3.1326.
NF-Y is a sequence-specific evolutionary conserved activator binding to CCAAT boxes with high affinity and specificity. It is a trimer formed by NF-YA and two putative histone-like subunits, NF-YB and NF-YC, showing similarity to histones H2B and H2A, respectively. We investigated the relationships between NF-Y and chromatin using an Artemia franciscana chromatin assembly system with plasmids containing the Major HistoCompatibility complex class II Ea promoter. The NF-Y trimer, but not single subunits, protects the Y box in the presence of reconstituted chromatin, and it can bind the target sequence during and after assembly. Using reconstitution assays with purified chicken histones, we show that NF-Y associates with preformed nucleosomes. Translational analysis of various Ea fragments of identical length in which the CCAAT box is at different positions indicated that the lateral fragment was slightly more prone to NF-Y binding. In competition experiments, NF-Y is able to prevent formation of nucleosomes significantly. These data support the idea that NF-Y is a gene-specific activator with a built-in capacity to interface with chromatin structures.
核因子Y（NF-Y）是一种序列特异性的进化保守激活因子，能以高亲和力和特异性结合CCAAT框。它是由NF-YA以及两个假定的类组蛋白亚基NF-YB和NF-YC形成的三聚体，分别与组蛋白H2B和H2A相似。我们使用卤虫染色质组装系统和含有主要组织相容性复合体II类Ea启动子的质粒，研究了NF-Y与染色质之间的关系。在重组染色质存在的情况下，NF-Y三聚体而非单个亚基能保护Y框，并且它在组装过程中和组装后都能结合靶序列。通过使用纯化的鸡组蛋白进行重组实验，我们表明NF-Y与预先形成的核小体相关联。对相同长度的各种Ea片段进行翻译分析，其中CCAAT框处于不同位置，结果表明侧翼片段稍微更易于与NF-Y结合。在竞争实验中，NF-Y能够显著阻止核小体的形成。这些数据支持这样一种观点，即NF-Y是一种具有与染色质结构相互作用内在能力的基因特异性激活因子。
