Transcription factor required in complex with TAF3 for the differentiation of myoblasts into myocytes. The complex replaces TFIID at specific promoters at an early stage in the differentiation process. Interacts with TAF3. Present in the cytoplasm during cytokinesis. Expressed in myotubes and myofibers (at protein level). Expressed in a wide variety of tissues with highest levels in heart, lung, liver, uterus and placenta and especially the gonads. Expression is higher in the ovary than the testis, and within the ovary expression is localized to the oocytes. Belongs to the TBP family.