Division of Geriatric Medicine, Department of Medicine, University of Pittsburgh, Pennsylvania, United States of America.
PLoS Genet. 2011 Jul;7(7):e1002179. doi: 10.1371/journal.pgen.1002179. Epub 2011 Jul 21.
The nuclear receptor DAF-12 has roles in normal development, the decision to pursue dauer development in unfavorable conditions, and the modulation of adult aging. Despite the biologic importance of DAF-12, target genes for this receptor are largely unknown. To identify DAF-12 targets, we performed chromatin immunoprecipitation followed by hybridization to whole-genome tiling arrays. We identified 1,175 genomic regions to be bound in vivo by DAF-12, and these regions are enriched in known DAF-12 binding motifs and act as DAF-12 response elements in transfected cells and in transgenic worms. The DAF-12 target genes near these binding sites include an extensive network of interconnected heterochronic and microRNA genes. We also identify the genes encoding components of the miRISC, which is required for the control of target genes by microRNA, as a target of DAF-12 regulation. During reproductive development, many of these target genes are misregulated in daf-12(0) mutants, but this only infrequently results in developmental phenotypes. In contrast, we and others have found that null daf-12 mutations enhance the phenotypes of many miRISC and heterochronic target genes. We also find that environmental fluctuations significantly strengthen the weak heterochronic phenotypes of null daf-12 alleles. During diapause, DAF-12 represses the expression of many heterochronic and miRISC target genes, and prior work has demonstrated that dauer formation can suppress the heterochronic phenotypes of many of these target genes in post-dauer development. Together these data are consistent with daf-12 acting to ensure developmental robustness by committing the animal to adult or dauer developmental programs despite variable internal or external conditions.
核受体 DAF-12 在正常发育、在不利条件下追求 dauer 发育的决策以及调节成年衰老中起作用。尽管 DAF-12 具有重要的生物学意义，但该受体的靶基因在很大程度上尚不清楚。为了鉴定 DAF-12 的靶基因，我们进行了染色质免疫沉淀，然后进行了全基因组平铺阵列杂交。我们鉴定出 1175 个基因组区域在体内被 DAF-12 结合，这些区域富含已知的 DAF-12 结合基序，并在转染细胞和转基因蠕虫中作为 DAF-12 反应元件发挥作用。这些结合位点附近的 DAF-12 靶基因包括一个广泛的异时和 microRNA 基因相互连接的网络。我们还鉴定了编码 miRISC 组件的基因，miRISC 是 microRNA 控制靶基因所必需的，它是 DAF-12 调节的靶基因。在生殖发育过程中，许多靶基因在 daf-12(0)突变体中失调，但这很少导致发育表型。相比之下，我们和其他人发现，null daf-12 突变增强了许多 miRISC 和异时靶基因的表型。我们还发现环境波动显著增强了 null daf-12 等位基因的微弱异时表型。在休眠期间，DAF-12 抑制许多异时和 miRISC 靶基因的表达，先前的工作表明 dauer 形成可以在 dauer 后发育过程中抑制许多这些靶基因的异时表型。这些数据表明，daf-12 通过将动物承诺为成年或 dauer 发育程序，确保了发育的稳健性，尽管内部或外部条件存在变化。
