Strauss J, Muro-Pastor M I, Scazzocchio C
Institut de Génétique et Microbiologie, Université Paris-Sud, URA D2225, Orsay, France.
Mol Cell Biol. 1998 Mar;18(3):1339-48. doi: 10.1128/MCB.18.3.1339.
The regulation of nitrate assimilation seems to follow the same pattern in all ascomycetes where this process has been studied. We show here by in vitro binding studies and a number of protection and interference techniques that the transcription factor mediating nitrate induction in Aspergillus nidulans, a protein containing a binuclear zinc cluster DNA binding domain, recognizes an asymmetrical sequence of the form CTCC GHGG. We further show that the protein binds to its consensus site as a dimer. We establish the role of the putative dimerization element by its ability to replace the analogous element of the cI protein of phage lambda. Mutagenesis of crucial leucines of the dimerization element affect both the binding ability of the dimer and the conformation of the resulting protein-DNA complex. This is the first case to be described where a dimer recognizes such an asymmetrical nonrepeated sequence, presumably by each monomeric subunit making different contacts with different DNA half-sites.
在所有已对硝酸盐同化作用进行研究的子囊菌中，硝酸盐同化作用的调控似乎遵循相同的模式。我们通过体外结合研究以及一系列保护和干扰技术表明，在构巢曲霉中介导硝酸盐诱导的转录因子是一种含有双核锌簇DNA结合结构域的蛋白质，它能识别CTCC GHGG形式的不对称序列。我们进一步表明，该蛋白质以二聚体形式与其共有位点结合。我们通过其取代噬菌体λ cI蛋白类似元件的能力确定了假定二聚化元件的作用。二聚化元件关键亮氨酸的诱变会影响二聚体的结合能力以及所得蛋白质 - DNA复合物的构象。这是首次描述的一种情况，即二聚体识别这样一个不对称的非重复序列，推测是每个单体亚基与不同的DNA半位点进行不同的接触。
