Xue D, Tu Y, Chalfie M
Department of Biological Sciences, Columbia University, New York, NY 10027.
Science. 1993 Sep 3;261(5126):1324-8. doi: 10.1126/science.8103239.
The POU-type homeodomain protein UNC-86 and the LIM-type homeodomain protein MEC-3, which specify neuronal cell fate in the nematode Caenorhabditis elegans, bind cooperatively as a heterodimer to the mec-3 promoter. Heterodimer formation increases DNA binding stability and, therefore, increases DNA binding specificity. The in vivo significance of this heterodimer formation in neuronal differentiation is suggested by (i) a loss-of-function mec-3 mutation whose product in vitro binds DNA well but forms heterodimers with UNC-86 poorly and (ii) a mec-3 mutation with wild-type function whose product binds DNA poorly but forms heterodimers well.
POU 型同源结构域蛋白 UNC-86 和 LIM 型同源结构域蛋白 MEC-3 在秀丽隐杆线虫中决定神经元细胞命运，它们作为异源二聚体协同结合到 mec-3 启动子上。异源二聚体的形成增加了 DNA 结合稳定性，因此也增加了 DNA 结合特异性。这种异源二聚体形成在神经元分化中的体内意义体现在以下两方面：（i）一个功能丧失的 mec-3 突变体，其产物在体外能很好地结合 DNA，但与 UNC-86 形成异源二聚体的能力较差；（ii）一个具有野生型功能的 mec-3 突变体，其产物结合 DNA 的能力较差，但形成异源二聚体的能力良好。
