The TBP-like factor CeTLF is required to activate RNA polymerase II transcription during C-elegans embryogenesis

Metazoans possess two TATA-binding protein homologs, the general transcript ion factor TBP and a related factor called TLF. Four models have been propo sed for the role of TLF in RNA polymerase II (Pol Il) transcription: (1) TL F and TBP function redundantly, (2) TLF antagonizes TBP, (3) TLF is a tissu e-specific TBP, or (4) TLF and TBP have distinct activities. Here we report that CeTLF is required to express a subset of Pol II genes and associates with at least one of these genes in vivo. CeTLF is also necessary to establ ish bulk transcription during early embryogenesis. Since CeTLF and CeTBP ar e expressed at comparable levels in the same cells, these findings suggest CeTLF performs a unique function in activating Pol II transcription distinc t from that of CeTBP.