TATA box-binding protein-associated factor RNA polymerase I subunit A is an enzyme that in humans is encoded by the TAF1A gene. This gene encodes a subunit of the RNA polymerase I complex, Selectivity Factor I (SLI). The encoded protein is a TATA box-binding protein-associated factor that plays a role in the assembly of the RNA polymerase I preinitiation complex. Alternate splicing results in multiple transcript variants encoding multiple isoforms.
Component of the transcription factor SL1/TIF-IB complex, which is involved in the assembly of the PIC (preinitiation complex) during RNA polymerase I-dependent transcription. The rate of PIC formation probably is primarily dependent on the rate of association of SL1/TIF-IB with the rDNA promoter. SL1/TIF-IB is involved in stabilization of nucleolar transcription factor 1/UBTF on rDNA. Formation of SL1/TIF-IB excludes the association of TBP with TFIID subunits.