DAF‐16 stabilizes the aging transcriptome and is activated in mid‐aged <i>Caenorhabditis elegans</i> to cope with internal stress

The roles and regulatory mechanisms of transcriptome changes during aging are unclear. It has been proposed that the transcriptome suffers decay during aging owing to age-associated down-regulation of transcription factors. In this study, we characterized the role of a transcription factor DAF-16, which is a highly conserved lifespan regulator, in the normal aging process of Caenorhabditis elegans. We found that DAF-16 translocates into the nucleus in aged wild-type worms and activates the expression of hundreds of genes in response to age-associated cellular stress. Most of the age-dependent DAF-16 targets are different from the canonical DAF-16 targets downstream of insulin signaling. This and other evidence suggest that activation of DAF-16 during aging is distinct from activation of DAF-16 due to reduced signaling from DAF-2. Further analysis showed that it is due in part to a loss of proteostasis(definition) during aging. We also found that without daf-16, dramatic gene expression changes occur as early as on adult day 2, indicating that DAF-16 acts to stabilize the transcriptome during normal aging. Our results thus reveal that normal aging is not simply a process in which the gene expression program descends into chaos due to loss of regulatory activities; rather, there is active transcriptional regulation during aging.