CONSTANS (CO) is a master regulator of flowering time, although the mechanisms underlying its role as a transcriptional regulator are not well understood. The DNA-binding domain of CO shares homology with that of NUCLEAR FACTOR YA (NF-YA), a subunit of the CCAAT-binding trimer NF-Y. Recent publications indicate that CO and its rice homolog HEADING DATE 1 (Hd1) form heterotrimers with the histone-fold subunits of NF-Y to efficiently bind promoter elements in the florigen genes. Differences in the DNA-binding specificities of NF-Y and NF-CO can be conceptualized based on our knowledge of the 3D structure of the NF-Y/CCAAT complex. Here we discuss the modes of assembly of NF-Y-like heterotrimers and possible models for their activity as flexible sequence-specific transcriptional regulators.

CONSTANS（CO）是开花时间的主要调节剂，尽管其作为转录调节剂的作用机理尚不清楚。CO的DNA结合结构域与CCAAT结合三聚体NF-Y的亚基NUCLEAR FACTOR YA（NF-YA）具有同源性。最近的出版物表明，CO及其水稻同源物HEADING DATE 1（Hd1）与NF-Y的组蛋白折叠亚基形成异源三聚体，以有效结合荧光原基因中的启动子元件。基于我们对NF-Y / CCAAT 3D结构的了解，可以概念化NF-Y和NF-CO的DNA结合特异性的差异复杂的。在这里，我们讨论了NF-Y样异源三聚体的组装模式，以及它们作为灵活的序列特异性转录调节因子的活性的可能模型。