E3 ubiquitin-protein ligase which promotes ubiquitination and subsequent degradation of host MHC-I and CD4 molecules, presumably to prevent lysis of infected cells by cytotoxic T-lymphocytes and NK cell. Binds target molecules through transmembrane interaction. The result of this ubiquitination is the enhancement of the endocytosis of the target chain and the delivery to the lysosome, where it is proteolytically destroyed (By similarity). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. The RING-CH-type zinc finger domain is required for E3 ligase activity. Belongs to the poxviridae LAP protein family.