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RNA po lymerase I prom oter region
The RNA polymerases promoters
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RNA polymerase III co re promoter
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Promoters used by RNA polymerase II have different
structures
depending upon the particular combination of transcription
factors that arerequired to build a functional transcriptional
complex at each promoter.
Nevertheless, these different structures can be viewed as a
combination
of a relatively limited number of specific sequence
elements.
Some of the common elements that have been described in class
II
eukaryotic promoters are the following:
The TATA Boxlocated approximately 30bp upstream of the
start-
point of transcription is found in many promoters. The
consenus
sequence of this element is TATAAAA(so it resembles the
TATAAT
sequence of the prokaryotic -10 regionbut please do not mix them
up).
RNA po lymerase II promoter
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RNA polym erase II promoter
The TATA box appears to be more important for selecting the
startpoint of transcription (i.e. positioning the enzyme) than
for
defining the promoter.
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The RNA polym erase II transcr ip t ional complex
http://bp2.blogger.com/_DZH2cmCoois/RgBKOBa8fwI/AAAAAAAABj4/Bn5Fc9ufJ2g/s1600-h/figure+21-13.jpg
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The holoenzyme consists of the RNA polymerase II complex,
the
regulatory complexes and the following transcription
factors:
1- TFIIBis a single polypeptide. It can bind both upstream
and
downstream of the TATA box. It recruits TFIIF-RNAPII to the
complex. It
may interact directly with RNAP II.
2- TFIIE is a complex of two subunits. It recruits TFIIH to the
complex
thereby priming the initiation complex for promoter clearance
andelongation.
3- TFIIFalso has two subunits - RAP38 & RAP74. The latter
has a
helicase activity and may therefore be involved in melting the
DNA at the
promoter to expose the template strand.
4- TFIIHis a complex of 9 subunits. One of the subunits has a
kinase
activity that carries out the phosphorylation that is required
for promoter
clearance
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Transc ript ion ini t iat ion
by RNA polym erase II
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Expression of mRNA in
Eukaryot ic c el ls requires
transcr ip t ion , mod if icat ion,
processing , nuc leo-cytoplasm ic
transport and translat ion
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The structure and formation of the 5 RNA cap
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Polyadenylat ion
and term ination
