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Attachment of one or more ubiquitins (Ubs) to various intracellular proteins has a number of roles in plants including the selective removal of regulatory proteins by the 26S proteasome. The final step in this modification is performed by ubiquitin‐protein ligases (E3s) that promote Ub transfer to appropriate targets. One important family of E3s is defined by the presence of a HECT domain, an active site first found at the C‐terminus of the human E3 (E6‐AP). Using a consensus HECT domain as the query, we identified a family of seven HECT‐containing ubiquitin‐protein ligases (UPL1–UPL7) in Arabidopsis thaliana that can be grouped into four subfamilies. The UPL3 and UPL4 subfamily encodes approximately 200‐kDa proteins with four Armadillo repeats similar to those in the nuclear pore protein importin‐α, suggesting that these E3s identify their targets through binding to nuclear localization sequences. Although …