E3 ubiquitin-protein ligase mediating 'Lys-48'-linked polyubiquitination of LIMK1 and its subsequent targeting to the proteasome for degradation. Negatively regulates axonal outgrowth through regulation of the LIMK1 turnover. Mediates 'Lys-6' and 'Lys-27'-linked polyubiquitination of AR/androgen receptor thereby modulating its transcriptional activity. May also bind DNA and function as a transcriptional regulator. 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. Interacts with AR (By similarity). Interacts with LIMK1. Localizes to the PML nuclear bodies in Sertoli cells. Widely expressed with higher expression in the testis in both germ cells and Sertoli cells. Expressed in the floor plate and ventral portions of the developing neural tube of 12.5 dpc to 13 dpc mouse embryos. Found in developing neuronal projections (at protein level). Belongs to the RNF12 family.