Probably enhances ubiquitin ligase activity of RING-type zinc finger-containing E3 ubiquitin-protein ligases, possibly through recruitment and/or stabilization of the Ubl-conjugating enzyme (E2) at the E3:substrate complex. Acts as a regulator of retrograde transport via its interaction with VPS35. Recruited to retromer-containing endosomes and promotes the formation of 'Lys-63'-linked polyubiquitin chains at 'Lys-220' of WASHC1 together with TRIM27, leading to promote endosomal F-actin assembly (By similarity). Regulates the circadian clock by repressing the transcriptional activator activity of the CLOCK-ARNTL/BMAL1 heterodimer. Significantly promotes the cytoplasmic accumulation of CLOCK (PubMed:22208286). Interacts with TRIM27. Interacts with VPS35; leading to recruitment at retromer-containing endosomes (By similarity). Interacts with ARNTL/BMAL1 and PER2. Recruited to retromer-containing endosomes via interaction with VPS35. Colocalizes with CLOCK and ARNTL/BMLA1 in the cytoplasm, and with PER2 in the cytoplasm and nucleus. Expressed predominantly in late development stages and adult brain. Deficient mice show reduced embryonic viability, neonatal growth retardation, excessive weight gain after weaning, and increased adiposity with altered metabolism, including increased fasting insulin and elevated cholesterol, in adulthood. Mutant mice also show abnormalities in the circadian pattern of feeding behavior. Deficient mice show features similar to those of Prader-Willi syndrome in humans. Truncated N-terminus. Truncated N-terminus.