week_9_lecture_1

2 tfiih phosphorylation of rnap ii ctd tfiih p

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Unformatted text preview: on by TFIID and the rest of GTFs and RECALL XP - XERODERMA PIGMENTOSUM • HUMAN EXCISION HUMAN REPAIR REPAIR • XPC-hHR23B XPC-hHR23B complex recognizes complex damage, binds & damage binds melts DNA melts • TFIIH helicase melts TFIIH more more • Endonucleases Endonucleases directed by RPA to RPA cut out damaged strand strand • DNA pol fills, ligase DNA seals seals Weaver 2002 Molecular Biology Ed. 2 TFIIH PHOSPHORYLATION OF RNAP II CTD TFIIH P labelled ATP added added 32 Weaver 2002 Molecular Biology Ed. 2 • TFIIH kinase phosphorylates CTD RNAP II tail TFIIH unphosphorylated preinitiation form (Pol IIA) ---> phosphorylated elongation form (Pol IIO) phosphorylated [Pol IIB lacks CTD and cannot be phosphorylated] • CTD tail alone (freed from RNAP with chymotrypsin [+Chym]) CTD phosphorylated by addition of TFIIH (+H) phosphorylated In vivo, transcription initiation requires additional proteins, including the Mediator complex A new set of factors stimulates RNA pol II elongation and RNA proofreading TFIIH P-TEFb Various proteins are through to stimulate elongation by pol II. One of these, kinase P-TEFb, is recruited to polymerase by transcriptional activators and, once bound, phosphorylates the serine residue at position 2 of the CTD repeats. Another factor, SPT5 (a universally conserved transcription factor across all three kingdoms of life), displaces initiation factors. Important because some promoters in higher eukaryotes recruit initiation complex effectively, but polymerase remains paused just after initiating transcription. Such promoters seem to be associated with genes that are poised to be expressed rapidly or in a highly coordinated fashion, and their expression is regulated through the recruitment of specific activators of the P-TEFb kinase, which releases them from their pause. β -GLOBIN PROMOTER: MUTAGENESIS REVEALS -GLOBIN UPSTREAM ELEMENTS UPSTREAM GC box GC (-90) CAAT box CAAT (approx -75) (approx TAT A box • Nucleotide changes introduced at every position 100bp Nucleotide upstream of β -GLOBIN start - most caused down mutations & clustered in 3 short regions: TATA box; CAAT TATA CAAT box (also associated with up mutations); GC box box GC (GGGCGG consensus) (GGGCGG β -GLOBIN PROMOTER: MUTAGENESIS REVEALS -GLOBIN UPSTREAM ELEMENTS UPSTREAM GC box GC (-90) CAAT box CAAT (approx -75) (approx TAT A box • 2 upstream elements are actually more effective upstream more components of the promoter than TATA components • CAAT box: one of first co...
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This note was uploaded on 03/26/2014 for the course MBB 321 taught by Professor Davidson during the Spring '11 term at Simon Fraser.

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