Precise control of gene expression levels is essential for normal cell functions, yet how they are defined and tightly maintained, particularly at intermediate levels, remains elusive. Here, using a series of newly developed sequencing, imaging, and functional assays, we uncover a class of transcription factors with dual roles as activators and repressors, referred to as condensate-forming level-regulating dual-action transcription factors (TFs). They reduce high expression but increase low expression to achieve stable intermediate levels. Dual-action TFs directly exert activating and repressing functions via condensate-forming domains that compartmentalize core transcriptional unit selectively. Clinically relevant mutations in these domains, which are linked to a range of developmental disorders, impair condensate selectivity and dual-action TF activity. These results collectively address a fundamental question in expression regulation and demonstrate the potential of level-regulating dual-action TFs as powerful effectors for engineering controlled expression levels.

基因表达水平的精确控制对于正常细胞功能至关重要，但如何定义和严格维持它们，特别是在中间水平，仍然难以捉摸。在这里，使用一系列新开发的测序、成像和功能测定，我们发现了一类具有激活子和阻遏子双重作用的转录因子，称为凝液形成水平调节双作用转录因子（TF）。它们降低高表达但增加低表达以达到稳定的中间水平。双作用转录因子通过选择性划分核心转录单元的凝结物形成结构域直接发挥激活和抑制功能。这些结构域中的临床相关突变与一系列发育障碍有关，会损害冷凝物选择性和双重作用 TF 活性。这些结果共同解决了表达调节中的一个基本问题，并证明了水平调节双作用转录因子作为工程控制表达水平的强大效应器的潜力。