The TFIID basal transcription factor complex plays a major role in the initiation of RNA polymerase II (Pol II)-dependent transcription (By similarity). TFIID recognizes and binds promoters via its subunit tbp-1, a TATA-box-binding protein, and promotes assembly of the pre-initiation complex (PIC) (By similarity). The TFIID complex consists of tbp-1 and TBP-associated factors (TAFs), including taf-5 (By similarity). Essential for early embryonic development, but not required for transcription of some genes; probably acts via activating transcription initiation by RNA Pol II, as part of the TFIID complex (PubMed:12458202). Component of the TFIID basal transcription factor complex, composed of TATA-box-binding protein tbp-1, and a number of TBP-associated factors (TAFs). Expressed in embryos (at protein level). RNAi-mediated knockdown causes arrested development at 90-100 cells and inhibits differentiation (PubMed:12458202). The two E cell daughters (E2 cells), which form the endoderm, divide abnormally early (PubMed:12458202). Phosphorylation of the RNA Pol II large subunit C-terminal domain (CTD) is reduced significantly in embryos (PubMed:12458202). Reduces expression of a range of genes, including let-858, rps-5, hsp16.2, and pes-10, but has little or no effect on expression of cki-2 and sur-5 (PubMed:12458202). Has little or no effect on levels of the TFIID subunits taf-10 and taf-4 (PubMed:12458202). Belongs to the WD repeat TAF5 family. The gene name for this protein was previously taf-4 (PubMed:11963920). The nomenclature was changed in PMID:11963920 and so readers should take care to avoid confusion (PubMed:11963920).