Unformatted text preview: anscription Kornberg and co-workers (2004) bound RNAP II to a set of
synthetic oligos (partial ds DNA template and a 10 nt RNA product
terminating in 3’-dA to trap polymerase in translocation state.
Soaked crystals of this complex with correct or mismatched
nucleotides striking differences revealed (A site and E site) Part of Rpb1 of Rpb1
Network of contacts with the
GTP substrate in A site.
The tripper loop of Rpb1
positions the substrate for
incorporation and discriminates
against improper nucleotides.
of Rpb2 With the Rpb4/7 in place the clamp is forced shut. Because initiation
occurs with the 12-subunit enzyme, with its clamp shut, it appears that the
promoter DNA must melt before the template DNA strand can descend
into the enzyme active site. It also appears that Rpb4/7 extends the dock
region of the polymerase, making it easier for certain general transcription
factors to bind, thereby facilitating transcription initiation OVERVIEW: RNAP II TRANSCRIPTION
OVERVIEW: • • Unlike prokaryote transcription: (1) RNAP II requires general factors at
promoter for basal transcription; (2) promoters can be controlled by
upstream factors, ubiquitous DNA-binding proteins that act on
promoters with consensus binding seq; (3) inducible factors activated at
specific times or in specific tissues regulate promoters at response
Eukaryote transcription unit: many regulatory seq found several kb upEukaryote
or downstream; no defined terminators; initial transcript contains coding
& noncoding regions EUKARYOTIC TRANSCRIPTION UNIT (RNAPII)
• PROMOTER: TATA box centered ~25bp upstream of
– Includes short elements (<10bp) that bind
transcription factors within ~200bp of start-site
– binds general transcription factors similar for all Pol II
• ENHANCERS: elements up to several kb up/downstream
-stimulate transcription initiation; bind specific
transcription MINIMUM REQUIREMENTS FOR RNAP II
• • (i) Generic RNAP II promoter: shortest nt sequence that supports
RNAP II transcriptional initiation - basal transcription apparatus
– Initiator (Inr): transcript start pt - no consensus seq; promoters
with just Inr are recognized by RNAP II
– many promoters have TATA box: ~25bp upstream from start site,
only element with fixed position & found in all eu...
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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.
- Spring '11