Substrate recognition component of a SCF (SKP1-CUL1-F-box protein) E3 ubiquitin-protein ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of target proteins. Recognizes and binds to phosphorylated target proteins (PubMed:10066435, PubMed:10497169, PubMed:10644755, PubMed:10835356, PubMed:11238952, PubMed:11359933, PubMed:11994270, PubMed:12791267, PubMed:12902344, PubMed:14603323, PubMed:14681206, PubMed:14988407, PubMed:15448698, PubMed:15917222, PubMed:16371461, PubMed:25503564, PubMed:25704143, PubMed:9859996, PubMed:22087322). SCF(BTRC) mediates the ubiquitination of CTNNB1 and participates in Wnt signaling (PubMed:12077367, PubMed:12820959). SCF(BTRC) mediates the ubiquitination of phosphorylated NFKB1, ATF4, CDC25A, DLG1, FBXO5, PER1, SMAD3, SMAD4, SNAI1 and probably NFKB2 (PubMed:10835356, PubMed:11238952, PubMed:14681206, PubMed:14603323). SCF(BTRC) mediates the ubiquitination of NFKBIA, NFKBIB and NFKBIE; the degradation frees the associated NFKB1 to translocate into the nucleus and to activate transcription (PubMed:10066435, PubMed:10497169, PubMed:10644755). Ubiquitination of NFKBIA occurs at 'Lys-21' and 'Lys-22' (PubMed:10066435). SCF(BTRC) mediates the ubiquitination of CEP68; this is required for centriole separation during mitosis (PubMed:25704143, PubMed:25503564). SCF(BTRC) mediates the ubiquitination and subsequent degradation of nuclear NFE2L1 (By similarity). Has an essential role in the control of the clock-dependent transcription via degradation of phosphorylated PER1 and PER2 (PubMed:15917222). May be involved in ubiquitination and subsequent proteasomal degradation through a DBB1-CUL4 E3 ubiquitin-protein ligase. Required for activation of NFKB-mediated transcription by IL1B, MAP3K14, MAP3K1, IKBKB and TNF. Required for proteolytic processing of GLI3 (PubMed:16371461). Mediates ubiquitination of REST, thereby leading to its proteasomal degradation (PubMed:21258371, PubMed:18354482). SCF(BTRC) mediates the ubiquitination and subsequent proteasomal degradation of KLF4; thereby negatively regulating cell pluripotency maintenance and embryogenesis (By similarity). Protein modification; protein ubiquitination. Homodimer. Self-associates. Component of the SCF(BTRC) complex formed of CUL1, SKP1, RBX1 and a BTRC dimer. Direct interaction with SKP1 occurs via the F-box domain. Interacts with phosphorylated ubiquitination substrates SMAD3 and SMAD4. Interacts with phosphorylated ubiquitination substrates CTNNB1, NFKBIA, NFKBIB, NFKBIE, NFKB1/nuclear factor NF-kappa-B p105 subunit, ATF4, CDC25A, DLG1, FBXO5 and SNAI1; the interaction requires the phosphorylation of the 2 serine residues in the substrate destruction motif D-S-G-X(2,3,4)-S. Binds UBQLN1. Interacts with CDC34 and UBE2R2. Interacts with FBXW11. Interacts with CUL4A and DDB1. Part of a SCF(BTRC)-like complex lacking CUL1, which is associated with phosphorylated NKBIA and RELA; RELA interacts directly with NFKBIA. Interacts with the phosphorylated form of GLI3. Interacts with CLU. Interacts with PER1 (phosphorylated), PER2 (phosphorylated) and PER3. Interacts with phosphorylated ubiquitination substrate CEP68 (PubMed:25704143, PubMed:25503564). Interacts with ZC3H12A; this interaction occurs when ZC3H12A is phosphorylated in a IKBKB/IKKB-dependent manner (By similarity). Interacts with HSF1; this interaction occurs during mitosis and induces HSF1 ubiquitin-dependent degradation, a process inhibited by CDC20 (PubMed:18794143). Interacts with NFE2L1 (By similarity). Interacts with INAVA (PubMed:29420262). Interacts with IL10RA; this interaction leads to IL10RA ubiquitination and subsequent degradation (PubMed:22087322). Interacts with REST (PubMed:18354482). Interacts with KLF4; this interaction leads to KLF4 ubiquitination and subsequent degradation (By similarity). (Microbial infection) Interacts with vaccinia virus A49; this interaction inhibits NF-kappa-B activation. (Microbial infection) Interacts with HIV-1 Vpu. Expressed in epididymis (at protein level). The N-terminal D domain mediates homodimerization.