The ULK1-ATG13-FIP200 complex is essential for autophagy and mediates mTOR signaling. This study identifies a novel protein complex containing ULK1, ATG13, and FIP200, all of which are essential for starvation-induced autophagy. FIP200 and ATG13 are critical for the correct localization of ULK1 to the pre-autophagosome and the stability of ULK1. The complex enhances ULK1 kinase activity individually, but both are required for maximal stimulation. ATG13 and ULK1 are phosphorylated by the mTOR pathway in a nutrient starvation-regulated manner, indicating that the complex acts as a node for integrating autophagy signals into autophagosome biogenesis. The complex is required for ULK1 localization to the isolation membrane and for ULK1 kinase activity. The study also shows that ULK1 can phosphorylate ATG13 and FIP200, suggesting that these proteins are substrates of the ULK1 kinase. The ULK1-ATG13-FIP200 complex is essential for autophagy and is regulated by mTOR-mediated phosphorylation. The complex is similar to the yeast Atg1-Atg13-Atg17 complex, but there are some differences in the regulation of the complex. The study provides evidence that the ULK1-ATG13-FIP200 complex is essential for autophagy and that the complex is regulated by mTOR-mediated phosphorylation. The study also shows that the complex is required for ULK1 localization to the isolation membrane and for ULK1 kinase activity. The study provides evidence that the ULK1-ATG13-FIP200 complex is essential for autophagy and that the complex is regulated by mTOR-mediated phosphorylation. The study also shows that the complex is required for ULK1 localization to the isolation membrane and for ULK1 kinase activity.The ULK1-ATG13-FIP200 complex is essential for autophagy and mediates mTOR signaling. This study identifies a novel protein complex containing ULK1, ATG13, and FIP200, all of which are essential for starvation-induced autophagy. FIP200 and ATG13 are critical for the correct localization of ULK1 to the pre-autophagosome and the stability of ULK1. The complex enhances ULK1 kinase activity individually, but both are required for maximal stimulation. ATG13 and ULK1 are phosphorylated by the mTOR pathway in a nutrient starvation-regulated manner, indicating that the complex acts as a node for integrating autophagy signals into autophagosome biogenesis. The complex is required for ULK1 localization to the isolation membrane and for ULK1 kinase activity. The study also shows that ULK1 can phosphorylate ATG13 and FIP200, suggesting that these proteins are substrates of the ULK1 kinase. The ULK1-ATG13-FIP200 complex is essential for autophagy and is regulated by mTOR-mediated phosphorylation. The complex is similar to the yeast Atg1-Atg13-Atg17 complex, but there are some differences in the regulation of the complex. The study provides evidence that the ULK1-ATG13-FIP200 complex is essential for autophagy and that the complex is regulated by mTOR-mediated phosphorylation. The study also shows that the complex is required for ULK1 localization to the isolation membrane and for ULK1 kinase activity. The study provides evidence that the ULK1-ATG13-FIP200 complex is essential for autophagy and that the complex is regulated by mTOR-mediated phosphorylation. The study also shows that the complex is required for ULK1 localization to the isolation membrane and for ULK1 kinase activity.