Negative regulator in the hedgehog/smoothened signaling pathway (PubMed:10559945, PubMed:10564661, PubMed:10806483, PubMed:12068298, PubMed:12975309, PubMed:27234298, PubMed:15367681, PubMed:22365972, PubMed:24217340, PubMed:24311597, PubMed:28965847). Down-regulates GLI1-mediated transactivation of target genes (PubMed:15367681, PubMed:24217340, PubMed:24311597). Down-regulates GLI2-mediated transactivation of target genes (PubMed:24311597, PubMed:24217340). Part of a corepressor complex that acts on DNA-bound GLI1. May also act by linking GLI1 to BTRC and thereby targeting GLI1 to degradation by the proteasome (PubMed:10559945, PubMed:10564661, PubMed:10806483, PubMed:24217340). Sequesters GLI1, GLI2 and GLI3 in the cytoplasm, this effect is overcome by binding of STK36 to both SUFU and a GLI protein (PubMed:10559945, PubMed:10564661, PubMed:10806483, PubMed:24217340). Negative regulator of beta-catenin signaling (By similarity). Regulates the formation of either the repressor form (GLI3R) or the activator form (GLI3A) of the full-length form of GLI3 (GLI3FL) (PubMed:24311597, PubMed:28965847). GLI3FL is complexed with SUFU in the cytoplasm and is maintained in a neutral state (PubMed:24311597, PubMed:28965847). Without the Hh signal, the SUFU-GLI3 complex is recruited to cilia, leading to the efficient processing of GLI3FL into GLI3R (PubMed:24311597, PubMed:28965847). When Hh signaling is initiated, SUFU dissociates from GLI3FL and the latter translocates to the nucleus, where it is phosphorylated, destabilized, and converted to a transcriptional activator (GLI3A) (PubMed:24311597, PubMed:28965847). Required for normal embryonic development (By similarity). Required for the proper formation of hair follicles and the control of epidermal differentiation (By similarity). May form homodimers (PubMed:10564661). Part of a DNA-bound corepressor complex containing SAP18, GLI1 and SIN3 (By similarity). Part of a complex containing CTNNB1 (By similarity). Binds BTRC, GLI2, GLI3, SAP18 and STK36 (PubMed:10564661, PubMed:10806483). Binds both free and DNA-bound GLI1 (PubMed:10559945, PubMed:15367681, PubMed:24217340, PubMed:24311597, PubMed:28965847). Interacts with KIF7 (By similarity). Interacts with GLI3FL and this interaction regulates the formation of either repressor or activator forms of GLI3 (PubMed:24311597, PubMed:28965847). Its association with GLI3FL is regulated by Hh signaling and dissociation of the SUFU-GLI3 interaction requires the presence of the ciliary motor KIF3A (PubMed:24311597, PubMed:28965847). Interacts with ULK3; inactivating the protein kinase activity of ULK3 (PubMed:20643644). Interacts with RAB23 (PubMed:22365972). Ubiquitous in adult tissues. Detected in osteoblasts of the perichondrium in the developing limb of 12-week old embryos. Isoform 1 is detected in fetal brain, lung, kidney and testis. Isoform 2 is detected in fetal testis, and at much lower levels in fetal brain, lung and kidney. Polyubiquitinated at Lys-257 by the SCF(FBXL17) complex, leading to its subsequent degradation and allowing the release of GLI1 for proper hedgehog/smoothened signal transduction (PubMed:27234298). Ubiquitination is impaired by phosphorylation at Ser-342, Ser-346, Ser-352 and Thr-353 (PubMed:27234298). Phosphorylation at Ser-342, Ser-346, Ser-352 and Thr-353 prevents ubiquitination by the SCF(FBXL17) complex. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Major isoform. Belongs to the SUFU family.