May function as a transcriptional repressor. May also function as a ubiquitin ligase. Functions in cell survival and proliferation through control of the cell cycle. 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. Protein modification; protein ubiquitination. A small fraction is detected in the cytoplasm.