TI - FIP200 , a ULK -interacting protein , is required for autophagosome formation in mammalian cells . AB - Autophagy is a membrane-mediated intracellular degradation system . The serine/threonine kinase Atg1 plays an essential role in autophagosome formation . However , the role of the mammalian Atg1 homologues UNC-51-like kinase ( ULK ) 1 and 2 are not yet well understood . We found that murine ULK1 and 2 localized to autophagic isolation membrane under starvation conditions . Kinase -dead alleles of ULK1 and 2 exerted a dominant-negative effect on autophagosome formation , suggesting that ULK kinase activity is important for autophagy . We next screened for ULK binding proteins and identified the focal adhesion kinase family interacting protein of 200 kD ( FIP200 ) , which regulates diverse cellular functions such as cell size , proliferation and migration . We found that FIP200 was redistributed from the cytoplasm to the isolation membrane under starvation conditions . In FIP200-deficient cells , autophagy induction by various treatments was abolished , and both stability and PHOSphorylation of ULK1 were impaired . These results suggest that FIP200 is a novel mammalian autophagy factor that functions together with ULKs .