Probable E3 ubiquitin-protein ligase, component of the TRAMP (TRF4) complex which has a poly(A) RNA polymerase activity and is involved in a post-transcriptional quality control mechanism limiting inappropriate expression of genetic information. Polyadenylation is required for the degradative activity of the exosome on several of its nuclear RNA substrates. 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. Component of the TRAMP complex (also called TRF4 complex) composed of at least HUL4, MTR4, PAP2/TRF4 and either AIR1 or AIR2. Belongs to the HUL4 family.