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 (By similarity). Interacts with TAF3. Present in the cytoplasm during cytokinesis. Ubiquitously expressed in all tissues examined with highest levels in heart, lung, ovary, spleen and testes. Belongs to the TBP family.