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Unformatted text preview: I. How s it different from prokaryotic (remember, PolII, sigma factor, -10 and -30 binding sites etc.): A. There s a nuclear membrane between the transcription machinery and the translation machinery- transcription and translation are no longer coupled B. Processing of mRNA (splicing, 5 cap, polyA tail) 1. Can get multiple splice variants C. Often requires remodeling of chromatin to overcome repression caused by nucleosomes and bundling of DNA D. Requires general transcription factors to get ANY transcription (not just RNA Pol and sigma anymore, now need TFII s) E. May require transcription factors speciFc to the gene F. Different polymerases for different RNA types 1. mRNA uses RNAPII, this is what we talk about G. More complicated promoter . Promoters can include many protein binding sites. Remember that these are DNA sequences , not proteins. These sequences can be present in many different combinations depending on the specic promoter. 1. Core promoter- 60bp around start site, serves as binding site for general transcription factors, namely TFIID and sometimes TFIIB a) TATA box- binding site for TBP (TBP is a subunit of TFIID that bends DNA) b) BRE (Beta Recognition Element)- a binding site for TFIIB 2. Proximal promote r- parts of the promoter that are close to the start site (includes core promoter) 3. Upstream Activating sequence- regulates TFIID binding to core promoter in yeast. Usually composed of binding sites for TF s 4. Insulator- chromatin boundary marker and/or enhancer blocker. Prevents cross-activation or repressing of genes by blocking the action of enhancers or silencers. 5. Enhancer- binding site for activating proteins (transcription factors) a) function independently of their orientation because they act over large distances making a huge loop of DNA b) Often cell-type specic- a specic enhancer can drive expression of a class of genes needed for a specic cell type c) Activating proteins are generally referred to as Transcription factors (not the general ones- TF s specic for this gene) 6. Silencer- binding site for repressing proteins II. General transcription machinery A. RNAPII does the actual catalysis of phosphodiester bonds to make RNA 1. Has a C-terminal domain (CTD) composed of 7amino acid repeat 2. CTD gets phosphorylated B. ive general transcription factors...
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- Fall '09