Fractionation of yeast extracts on heparin-agarose revealed the presence of a DNA footprinting activity that interacted specifically with the 5'-upstream region of TEFI and TEF2 genes coding for the protein synthesis elongation factor EF-la, and of the ribosomal protein gene RPSIA.
Most class B (II) promoter regions from higher eukaryotes contain the TATA box and upstream and enhancer elements. Both the upstream and enhancer elements and their cognate factors have regulatory functions, whereas the TATA sequence interacts with the TATA box factor BTF1 to position RNA polymerase B and its ancillary initiation factors (STF, BTF2 and BTF3) to direct the initiation of transcription approximately 30 base pairs downstream. In many respects, class B promoter regions from the unicellular eukaryote Saccharomyces cerevisiae are similarly organized, containing upstream activating sequences that bear many similarities to enhancers. Although they are essential for initiation, the yeast TATA sequences are located at variable distances and further from the start sites (40-120 base pairs), whose locations are primarily determined by an initiator element. The basic molecular mechanisms that control initiation of transcription are known to be conserved from yeast to man: the yeast transcriptional transactivator GAL4 can activate a minimal TATA box-containing promoter in human HeLa cells, and a human inducible enhancer factor, the oestrogen receptor, can activate a similar minimal promoter in yeast. This striking evolutionary conservation prompted us to look for the presence in yeast of an activity that could possibly substitute for the human TATA box factor. We report here the existence of such an activity in yeast extracts.
Fractionation of transcription extracts has led to the identification of multiple transcription factors specific for each form of nuclear RNA polymerase. Accurate transcription in vitro of the yeast U6 RNA gene by RNA polymerase C requires at least two factors. One of them was physically and functionally indistinguishable from transcription factor IID (TFIID or BTF1), a pivotal component of polymerase B transcription complexes, which binds to the TATA element. Purified yeast TFIID (yIID) or bacterial extracts that contained recombinant yIID were equally competent to direct specific transcription of the U6 gene by RNA polymerase C. The results suggest the formation of a hybrid transcription machinery, which may imply an evolutionary relation between class B and class C transcription factors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.