Activation and Repression Mechanisms in Yeast
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Excerpt
In eukaryotes, gene expression depends on activatorproteins that bind enhancer elements and stimulate transcription by RNA polymerase II (pol II) (Struhl 1995;Zawel and Reinberg 1995). This general requirement foractivators is inferred from numerous observations invivo that intact promoters are much more efficientlytranscribed than core promoter derivatives containingonly the TATA and initiator elements. The pol II transcription machinery is complex and has a molecularweight comparable to that of a ribosome. The pol II machinery is composed of two basic components, TFIIDand the pol II holoenzyme. The TFIID complex, whichcontains the TATA-binding protein (TBP) and TBP-associated factors (TAFs), specifically binds the core promoter region; TBP interacts with high affinity and specificity for TATA elements, whereas certain TAFs caninteract with some specificity for initiator and downstream elements (Burley and Roeder 1996; Verrijzer andTjian 1996; Burke and Kadonaga 1997). The pol IIholoenzyme contains the core subunits of the enzyme,basic transcription factors (e.g., TFIIB), as well as Srb,Med, and a variety of other proteins (Koleske and Young1995; Myers et al. 1998)...
