The TAF3 protein is part of the basal transcription factor TFIID. Recently it was shown that a PHD finger in the C-terminus of the protein directly binds to trimethylated histone H3 lysine four, a histone mark associated with promoters that are actively being transcribed. Transcription initiation factor TFIID subunit 3 is a protein that in humans is encoded by the TAF3 gene.

The highly conserved RNA polymerase II transcription factor TFIID (see TAF1; MIM 313650) comprises the TATA box-binding protein (TBP; MIM 600075) and a set of TBP-associated factors (TAFs), including TAF3. TAFs contribute to promoter recognition and selectivity and act as antiapoptotic factors (Gangloff et al., 2001 [PubMed 11438666]).[supplied by OMIM, May 2009].
Function: Transcription factor TFIID is one of the general factors required for accurate and regulated initiation by RNA polymerase II. TFIID is a multimeric protein complex that plays a central role in mediating promoter responses to various activators and repressors. Required in complex with TBPL2 for the differentiation of myoblasts into myocytes. The complex replaces TFIID at specific promoters at an early stage in the differentiation process.