E3 ubiquitin ligase catalyzing the covalent attachment of ubiquitin moieties onto substrate proteins (PubMed:28378844). Promotes the polyubiquitination and proteasome-dependent degradation of RELA/p65, thereby suppressing RELA-mediated NF-kappa-B transactivation and negatively regulating inflammatory responses (PubMed:28378844). Plays a role in the regulation of spermiation and in male fertility (PubMed:28008940). 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 PDLIM2 (via LIM zinc-binding domain) (PubMed:28378844). Interacts with RELA (PubMed:28378844). Highly expressed in the testis, and lower expression in the brain, thymus, heart, lung, liver, spleen, kidney, ovary, uterus, and seminal vesicle (at protein level) (PubMed:28008940). Expressed in primary immune cells, such as CD4-positive and CD8-positive T cells, CD19-positive B cells and CD11c-positive dendritic cells, and in embryonic fibroblasts (at protein level) (PubMed:28378844). Male and female knockout mice are viable with a lighter birthweight than wild-type animals (PubMed:28008940). Causes infertility in male mice, whereas female mice are fertile, but display reduced fecundity (PubMed:28008940). Leads to abnormal sperms characterized by low number, poor motility, and aberrant morphology (PubMed:28008940). Sperms have deformed heads with abnormal or missing acrosomes, disorganized axonemal structure, and disorganized flagellar structure (PubMed:28008940). Complete loss of the axoneme doublets in one side of the fibrous sheath and disordered assembly of axoneme doublets (PubMed:28008940). Causes failure of sperm release (spermiation failure) and misarrangement of ectoplasmic specialization in testes, thus impairing spermiogenesis and spermiation (PubMed:28008940). Disrupted arrangement of ectoplasmic specialization, the adhesion junction found in Sertoli cells at sites of attachment to elongated spermatids or neighboring Sertoli cells in the testes, and decreased expression of Espn (PubMed:28008940). The outer dense fiber, which is an important component of flagellae, is absent or improperly arranged in epididymal sperms (PubMed:28008940). Decreased expression levels of Odf2 in spermatogenesis (PubMed:28008940).