TATA Box Binding Protein Associated Factor 1B (TAF1B)

Eukaryotic RNA polymerases are unable to initiate RNA synthesis in the absence of additional proteins called general transcription factors, or GTFs. The multisubunit complex SL1 is required for RNA polymerase I to synthesize ribosomal RNA. SL1 consists of TATA box-binding protein (TBP), which is a universal GTF for all 3 RNA polymerases, and 3 TBP-associated factors (TAFs).The TAF1B cDNA encodes a deduced 556-amino acid protein, which the authors suggested is missing a few amino acids at the N terminus. Western blot analysis confirmed that TAF1B is expressed as a 63-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.