Transcriptional activator (PubMed:15556296, PubMed:31932482). Binds DNA on GT-box consensus sequence 5'-TTGGTT-3' (PubMed:15556296). Plays a role in spermiogenesis (PubMed:31932482). Interacts with TAF4B. Expressed widely in testis, in both germline and somatic cells (PubMed:31932482). Seems to have particularly strong expression in meiotic spermatocytes, postmeiotic round spermatids and Sertoli cells (PubMed:31932482). Not detected in elongating spermatids or mature sperm (at protein level) (PubMed:31932482). Expressed in testis, ovary, spleen, lung, brain, liver and kidney (PubMed:15556296, PubMed:31932482). Expressed in D3 embryonic stem cells and F9 embryonal carcinoma cells (PubMed:15556296). During development, expression in the brain decreases gradually (PubMed:15556296). Shows increasing expression in testis from 16.5 dpc onwards, with maximum expression at postnatal day 21 (PubMed:31932482). Viable, with no gross morphological or behavioral phenotypes. Males are infertile with complete absence of mature sperm. Spermiogenesis arrests at the round spermatid stage, accompanied by extensive apoptosis within the seminiferous tubules. Expression of spermiogenesis-associated genes TNP1, TNP2, PRM1 and PRM2 in testis is significantly reduced. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.