TATA Box Binding Protein Associated Factor 1A (TAF1A)

Initiation of transcription by RNA polymerase I requires the formation of a complex composed of the TATA-binding protein (TBP) and three TBP-associated factors (TAFs) specific for RNA polymerase I. This complex, known as SL1, binds to the core promoter of ribosomal RNA genes to position the polymerase properly and acts as a channel for regulatory signals.TAF1A encodes the smallest SL1-specific TAF. Two transcripts encoding different isoforms have been identified.Western blot analysis confirmed that TAF1A is expressed as a 48-kD protein. Analysis of SL1 subunit interactions showed that all 3 TAF1 proteins bind to TBP and to each other. However, binding of the SL1 complex to TBP excluded binding of the RNA polymerase II transcription factor TFIID to TBP.