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 (PubMed:23452853). Regulates the circadian clock by repressing the transcriptional activator activity of the CLOCK-ARNTL/BMAL1 heterodimer. Significantly promotes the cytoplasmic accumulation of CLOCK (By similarity). Interacts with TRIM27. Interacts with VPS35; leading to recruitment at retromer-containing endosomes. Interacts with ARNTL/BMAL1 and PER2 (By similarity). 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 (By similarity). Expressed in placenta, fetal and adult brain. Not detected in heart and small intestine, very low levels in fibroblasts. Not expressed in brain of a Prader-Willi patient. The disease is caused by variants affecting the gene represented in this entry. All mutations occurred on the paternal allele. Imprinted, expressed from the paternal chromosome only.