Mantovani R
Dipartimento di Genetica e Biologia dei Microrganismi, Università di Milano, Via Celoria 26, 20133 Milano, Italy.
Nucleic Acids Res. 1998 Mar 1;26(5):1135-43. doi: 10.1093/nar/26.5.1135.
The CCAAT box is one of the most common elements in eukaryotic promoters, found in the forward or reverse orientation. Among the various DNA binding proteins that interact with this sequence, only NF-Y (CBF, HAP2/3/4/5) has been shown to absolutely require all 5 nt. Analysis of a database with 178 bona fide NF-Y binding sites in 96 unrelated promoters confirms this need and points to specific additional flanking nucleotides (C, Pu, Pu on the 5'-side and C/G, A/G, G,A/C, G on the 3'-side) required for efficient binding. The frequency of CCAAT boxes appears to be relatively higher in TATA-less promoters, particularly in the reverse ATTGG orientation. In TATA-containing promoters the CCAAT box is preferentially located in the -80/-100 region (mean position -89) and is not found nearer to the Start site than -50. In TATA-less promoters it is usually closer to the +1 signal (at -66 on average) and is sometimes present in proximity to the Cap site. The consensus and location of NF-Y binding sites parallel almost perfectly a previous general statistical study on CCAAT boxes in 502 unrelated promoters. This is an indication that NF-Y is the major, if not the sole, CCAAT box recognizing protein and that it might serve different roles in TATA-containing and TATA-less promoters.
CCAAT框是真核生物启动子中最常见的元件之一，可正向或反向存在。在与该序列相互作用的各种DNA结合蛋白中，只有NF-Y（CBF、HAP2/3/4/5）已被证明绝对需要所有5个核苷酸。对一个包含96个不相关启动子中178个真正的NF-Y结合位点的数据库进行分析，证实了这种需求，并指出了有效结合所需的特定额外侧翼核苷酸（5'端为C、嘌呤、嘌呤，3'端为C/G、A/G、G、A/C、G）。CCAAT框在无TATA框的启动子中出现频率相对较高，尤其是反向的ATTGG方向。在含有TATA框的启动子中，CCAAT框优先位于-80/-100区域（平均位置-89），且在距起始位点-50以内未发现。在无TATA框的启动子中，它通常更靠近+1信号（平均在-66处），有时也存在于帽位点附近。NF-Y结合位点的共有序列和位置几乎与之前对502个不相关启动子中CCAAT框的一般统计研究完全一致。这表明NF-Y即使不是唯一的，也是主要的CCAAT框识别蛋白，并且它可能在含有TATA框和无TATA框的启动子中发挥不同作用。
