Walleye dermal sarcoma (WDS) is a benign tumor of walleye fish that develops and completely regresses seasonally. The retrovirus associated with this disease, walleye dermal sarcoma virus, encodes three proteins: gag, pol, and env. The gag protein is responsible for the structural components of the virus, while the pol protein is involved in the replication of the virus. The env protein is responsible for the attachment of the virus to the host cell. The study of WDS virus is important for understanding the mechanisms of tumor development and regression in fish, and may also provide insights into the development of similar tumors in humans.