Florence B, Handrow R, Laughon A
Departments of Genetics, University of Wisconsin, Madison 53706.
Mol Cell Biol. 1991 Jul;11(7):3613-23. doi: 10.1128/mcb.11.7.3613-3623.1991.
The fushi tarazu (ftz) gene of Drosophila melanogaster encodes a homeodomain-containing transcription factor that functions in the formation of body segments. Here we report an analysis of the DNA-binding properties of the ftz homeodomain in vitro. We provide evidence that the homeodomain binds to DNA as a monomer, with an equilibrium dissociation constant of 2.5 x 10(-11) M for binding to a consensus binding site. A single ftz binding site occupies 10 to 12 bp, as judged by the ability of protein bound at one site to interfere with binding to an adjacent site. These experiments also demonstrated a lack of cooperative binding between ftz homeodomains. Analysis of single-nucleotide substitutions over an 11-bp sequence shows that a stretch of 6 bp is critical for binding, with an optimal sequence of 5'CTAATTA3'. These data correlate well with recent structural evidence for base-specific contact at these positions. In addition, we found that sequences flanking the region of direct contact have effects on DNA binding that could be of biological significance.
黑腹果蝇的无翅基因（ftz）编码一种含同源结构域的转录因子，其在体节形成中发挥作用。在此，我们报告了对ftz同源结构域体外DNA结合特性的分析。我们提供的证据表明，该同源结构域以单体形式与DNA结合，与共有结合位点结合的平衡解离常数为2.5×10⁻¹¹ M。根据一个位点结合的蛋白质干扰相邻位点结合的能力判断，单个ftz结合位点占据10至12个碱基对。这些实验还表明ftz同源结构域之间缺乏协同结合。对11个碱基对序列上的单核苷酸取代进行分析表明，一段6个碱基对的序列对结合至关重要，最佳序列为5'CTAATTA3'。这些数据与近期关于这些位置碱基特异性接触的结构证据高度相关。此外，我们发现直接接触区域两侧的序列对DNA结合有影响，这可能具有生物学意义。
