In the host plant, component of SCF(virF) E3 ubiquitin ligase complexes, which mediate the ubiquitination and subsequent proteasomal degradation of target proteins such as the host VIP1, after its implication in T-DNA translocation to the host nucleus (By similarity). Required for the formation of tumors of a wild-type size on certain plant species only. Component of SCF(virF) E3 ubiquitin ligase complexes. Interacts with host VIP1 and SKP1A (By similarity). Interacts with Arabidopsis thaliana ENAP1/VFP3 and VFP5 in the host cell nucleus (PubMed:26571494).