Down-regulates ESR1 protein levels through the ubiquitination-proteasome pathway, regardless of the presence of 17 beta-estradiol. Also involved in 17 beta-estradiol-induced ESR1 degradation. Controls PGR protein levels through a similar mechanism. May predict the clinical outcome of tamoxifen therapy of breast cancer patients. Patients with tumors that highly express CUEDC2 do not respond to tamoxifen treatment as effectively as those with tumors with low expression. Belongs to the CUEDC2 family. Note: This description may include information from UniProtKB.