Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex. May play a role in accumulation of expanded polyglutamine (polyQ) protein huntingtin (HTT). Protein modification; protein ubiquitination. Part of a SCF (SKP1-cullin-F-box) protein ligase complex consisting of FBXO25, SKP1, CUL1 and RBX1. Interacts directly with SKP1 and CUL1. Interacts (via C-terminus) with beta-actin (via N-terminus) (By similarity). In the nucleus, associates with a specific and novel subnuclear dot-like structure. Colocalized with SKP1. Expressed in all tissues tested, except striated muscle (at protein level). Expressed predominantly in the cerebral cortex, the hippocampus and the Purkinje cell layer of the brain. Intestine and kidney show also significant levels. Expressed in neuronal tissues of 14.5 dpc mice. The F-box is necessary for the interaction with SKP1.