Elimination of the proliferating germline extends lifespan in C. elegans. This phenomenon provides a unique platform to understand how complex metazoans retain metabolic homeostasis when challenged with major physiological perturbations. Here, we demonstrate that two conserved transcription regulators essential for the longevity of germline-less adults, DAF-16/FOXO3A and TCER-1/TCERG1, concurrently enhance the expression of multiple genes involved in lipid synthesis and breakdown, and that both gene classes promote longevity. Lipidomic analyses revealed that key lipogenic processes, including de novo fatty acid synthesis, triglyceride production, desaturation and elongation, are augmented upon germline removal. Our data suggest that lipid anabolic and catabolic pathways are coordinately augmented in response to germline loss, and this metabolic shift helps preserve lipid homeostasis. DAF-16 and TCER-1 also perform essential inhibitory functions in germline-ablated animals. TCER-1 inhibits the somatic gene-expression program that facilitates reproduction and represses anti-longevity genes, whereas DAF-16 impedes ribosome biogenesis. Additionally, we discovered that TCER-1 is critical for optimal fertility in normal adults, suggesting that the protein acts as a switch supporting reproductive fitness or longevity depending on the presence or absence of the germline. Collectively, our data offer insights into how organisms adapt to changes in reproductive status, by utilizing the activating and repressive functions of transcription factors and coordinating fat production and degradation.

Histone post-translational modifications have been shown to contribute to DNA damage repair. Prior studies have suggested that specific H3K79 methylation states play distinct roles in the response to UV-induced DNA damage. To evaluate these observations, we examined the effect of altered H3K79 methylation patterns on UV-induced G1/S checkpoint response and sister chromatid exchange (SCE). We found that the di- and trimethylated states both contribute to activation of the G1/S checkpoint to varying degrees, depending on the synchronization method, although methylation is not required for checkpoint in response to high levels of UV damage. In contrast, UV-induced SCE is largely a product of the trimethylated state, which influences the usage of gene conversion versus popout mechanisms. Regulation of H3K79 methylation by H2BK123 ubiquitylation is important for both checkpoint function and SCE. H3K79 methylation is not required for the repair of double-stranded breaks caused by transient HO endonuclease expression, but does play a modest role in survival from continuous exposure. The overall results provide evidence for the participation of H3K79 methylation in UV-induced recombination repair and checkpoint activation, and further indicate that the di- and trimethylation states play distinct roles in these DNA damage response pathways.

Integrin adhesion complexes regulate cytoskeletal dynamics during cell migration. Adhesion activates phosphorylation of integrin-associated signaling proteins, including Cas (p130Cas, BCAR1), by Src-family kinases. Cas regulates leading-edge protrusion and migration in cooperation with its binding partner, BCAR3. However, it has been unclear how Cas and BCAR3 cooperate. Here, using normal epithelial cells, we find that BCAR3 localization to integrin adhesions requires Cas. In return, Cas phosphorylation, as well as lamellipodia dynamics and cell migration, requires BCAR3. These functions require the BCAR3 SH2 domain and a specific phosphorylation site, Tyr 117, that is also required for BCAR3 downregulation by the ubiquitin-proteasome system. These findings place BCAR3 in a co-regulatory positive-feedback circuit with Cas, with BCAR3 requiring Cas for localization and Cas requiring BCAR3 for activation and downstream signaling. The use of a single phosphorylation site in BCAR3 for activation and degradation ensures reliable negative feedback by the ubiquitin-proteasome system.