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CAND2/TIP120B is a large HEAT/ARM-repeat cullin-binding protein of the CAND family that regulates cullin-RING ligases (CRLs) and is not itself an enzyme; it is the muscle-enriched paralog of CAND1.
"Primary literature explicitly equates TIP120B with CAND2 and places it in the **CAND family** of large HEAT/ARM-repeat cullin-binding proteins involved in **cullin-RING ligase (CRL)** regulation (not an enzyme itself)."
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CAND-family proteins preferentially bind unneddylated cullins; CAND-bound cullins cannot be neddylated and neddylated cullins do not stably bind CAND, placing CAND2 in the NEDD8/CSN CRL-remodeling cycle.
"CAND-family proteins (classically CAND1, by inference also CAND2) preferentially associate with **unneddylated** cullins; structural/mechanistic work emphasizes that **CAND-bound cullins cannot be neddylated**, and **neddylated cullins do not stably bind CAND**"
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Human CAND2 binds the CUL1·RBX1 core and functions as an F-box-protein exchange factor that promotes SCF-mediated degradation, analogous to CAND1 but less efficient (higher KM / faster koff).
"a 2025 Nature Communications study (received Feb 2024) showing that human CAND2 can **promote SCF-mediated protein degradation** by functioning as an **F-box protein exchange factor** interacting with the CUL1·RBX1 core, analogous to CAND1 but less efficient"
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In skeletal muscle (C2C12), CAND2/TIP120B is induced during myogenic differentiation, binds CUL1, suppresses SCF-dependent ubiquitination and degradation of myogenin, and accelerates differentiation.
"is induced during myogenic differentiation,"
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CAND1 and CAND2 can contribute nonredundantly to optimal SCF activity; in the SCF(FBXL5)-IRP2 pathway loss of either slows IRP2 degradation, and ectopic CAND2 rescues an SCF substrate (p-IkBalpha) in CAND1/CAND2 double-knockout cells.
"in the **SCFFBXL5–IRP2** pathway, IRP2 half-life increased **2.8-fold in DKO**, **1.7-fold in CAND1-KO**, and **1.8-fold in CAND2-KO**, indicating both proteins contribute to optimal SCF function in that context"