Tri cluster is responsible for the biosynthesis of trichothecenes in Trichoderma spp. Tri6 gene present within the cluster encodes for a transcriptional regulator and is vital for the expression of all other tri genes of the cluster. Tri6 encodes for a 218-amino-acid residues long protein which contains three zinc finger motifs. Tri6 is able to regulate and bind within the GTGA/TCAC promoter region of tri genes. Here we highlight the binding of tri6 with the regulatory DNA element present at the upstream of tri3 gene and effect of two quorum-sensing molecules tyrosol and farnesol on its binding. Analysis showed that tyrosol binds at sequence GTGA/TCAC specific for tri6 binding and thus do not allow tri6 to bind on promoter region. Interactions of tyrosol with zinc finger motif of tri6 protein also resulted in structural changes making tri6 unsuitable for binding with the regulatory DNA element of tri3 gene promoter resulting in downregulation of the gene. Structural changes also resulted in loss of zinc from zinc finger 2 motif. In contrast to the tyrosol, tri6-DNA complex could easily accommodate farnesol molecule without showing any interference with the functional conformation of the tri6-DNA complex. Therefore, tri gene expression seems not to be negatively regulated by the farnesol.

三簇负责木霉属中木霉菌的生物合成。存在于簇中的Tri6基因编码转录调节子，并且对于簇中所有其他三基因的表达至关重要。Tri6编码一个218个氨基酸残基的长蛋白，其中包含三个锌指基序。Tri6能够调节并结合在tri基因的GTGA / TCAC启动子区域内。在这里，我们强调了tri6与存在于tri3上游的调控DNA元件的结合基因和两个群体感应分子酪醇和法尼醇对其结合的影响。分析表明，酪醇在特异于tri6结合的序列GTGA / TCAC处结合，因此不允许tri6在启动子区域结合。酪醇与tri6蛋白的锌指基序的相互作用也导致结构变化，使得tri6不适合与tri3基因启动子的调节DNA元件结合，从而导致该基因的下调。结构变化还导致锌指2基序丢失锌。与酪醇相反，tri6-DNA复合物可以轻松容纳法尼醇分子，而不会显示出对tri6-DNA复合物功能构象的任何干扰。因此，三基因表达似乎不受法尼醇的负调控。