General transcription factor that functions at the core of the DNA-binding multiprotein factor TFIID. Binding of TFIID to the TATA box is the initial transcriptional step of the pre-initiation complex (PIC), playing a role in the activation of eukaryotic genes transcribed by RNA polymerase II. Component of a BRF2-containing transcription factor complex that regulates transcription mediated by RNA polymerase III. Component of the transcription factor SL1/TIF-IB complex, which is involved in the assembly of the PIC (pre-initiation complex) during RNA polymerase I-dependent transcription. The rate of PIC formation probably is primarily dependent on the rate of association of SL1 with the rDNA promoter. SL1 is involved in stabilization of nucleolar transcription factor 1/UBTF on rDNA. Binds DNA as monomer. Belongs to the TFIID complex together with the TBP-associated factors (TAFs). Part of a TFIID-containing RNA polymerase II pre-initiation complex that is composed of TBP and at least GTF2A1, GTF2A2, GTF2E1, GTF2E2, GTF2F1, GTF2H2, GTF2H3, GTF2H4, GTF2H5, GTF2B, TCEA1, ERCC2, ERCC3, TAF1, TAF2, TAF3, TAF4, TAF5, TAF6, TAF7, TAF8, TAF9, TAF10, TAF11, TAF12 and TAF13. Component of the transcription factor SL1/TIF-IB complex, composed of TBP and at least TAF1A, TAF1B, TAF1C and TAF1D. Association of TBP to form either TFIID or SL1/TIF-IB appears to be mutually exclusive. Interacts with TAF1A, TAF1B and TAF1C. Interacts with TFIIB, NCOA6, DRAP1, DR1 and ELF3. Interacts with SPIB, SNAPC1, SNAPC2 and SNAPC4. Interacts with UTF1. Interacts with BRF2; this interaction promotes recruitment of BRF2 to TATA box-containing promoters. Interacts with UBTF. Interacts with GPBP1. Interacts with CITED2. Interacts with ATF7IP. Interacts with LLPH. Interacts with HSF1 (via transactivation domain). Interacts with GTF2B (via C-terminus); this interaction with promoter-bound TBP guides RNA polymerase II into the pre-initiation complex (PIC). Interacts with PAX5 (By similarity). Belongs to the TBP family.