Liu Hanwenheng, Earley Brian, Mendoza Adelita, Hunt Patrick, Teng Sean, Schneider Daniel Luke, Kornfeld Kerry
Department of Developmental Biology, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO 63110, USA.
G3 (Bethesda). 2025 May 23. doi: 10.1093/g3journal/jkaf089.
Enhancers play critical roles in gene expression, but a full understanding of their complex functions has yet to be defined. The cellular response to excess zinc levels in Caenorhabditis elegans requires the HIZR-1 transcription factor, which binds the high-zinc activation (HZA) enhancer in the promoters of multiple target genes. Cadmium hijacks the excess zinc response by binding and activating HIZR-1. By analyzing the genome-wide transcriptional response to excess zinc and cadmium, we identified two positions in the genome where head-to-head oriented genes are both induced by metals. In both examples, a single predicted HZA enhancer is positioned between the two translational start sites. We hypothesized that a single enhancer can control both head-to-head genes, an arrangement that has not been extensively characterized. To test this hypothesis, we used CRISPR genome editing to precisely delete the HZAmT enhancer positioned between mtl-2 and T08G5.1; in this mutant, both head-to-head genes display severely reduced zinc-activated transcription, whereas zinc-activated transcription of more distant genes was not strongly affected. Deleting the HZAcF enhancer positioned between cdr-1 and F35E8.10 caused both head-to-head genes to display reduced cadmium-activated transcription, whereas cadmium-activated transcription of more distant genes was not strongly affected. These studies rigorously document that a single HZA enhancer can control two head-to-head genes, advancing our understanding of the diverse functions of enhancers.
增强子在基因表达中发挥着关键作用，但对其复杂功能的全面理解尚未明确。秀丽隐杆线虫对过量锌水平的细胞反应需要HIZR-1转录因子，该因子与多个靶基因启动子中的高锌激活（HZA）增强子结合。镉通过结合并激活HIZR-1来劫持过量锌反应。通过分析对过量锌和镉的全基因组转录反应，我们在基因组中确定了两个位置，在这两个位置上，头对头排列的基因均被金属诱导。在这两个例子中，一个预测的单一HZA增强子位于两个翻译起始位点之间。我们推测一个单一的增强子可以控制两个头对头排列的基因，这种排列方式尚未得到广泛研究。为了验证这一假设，我们使用CRISPR基因组编辑技术精确删除了位于mtl-2和T08G5.1之间的HZAmT增强子；在这个突变体中，两个头对头排列的基因的锌激活转录均显著降低，而距离更远的基因的锌激活转录没有受到强烈影响。删除位于cdr-1和F35E8.10之间的HZAcF增强子导致两个头对头排列的基因的镉激活转录降低，而距离更远的基因的镉激活转录没有受到强烈影响。这些研究严格证明了一个单一的HZA增强子可以控制两个头对头排列的基因，增进了我们对增强子多样功能的理解。
