General Transcription Factors:
Introduce the concept of general transcription factors (GTFs) and their role in transcription initiation.
Explain how GTFs help RNA polymerase bind to the promoter and initiate transcription.
Highlight the significance of GTFs in regulating gene expression in var...
Chapter 7 Operon and Chapter 8: Major Shift in Transcription
RNA Processing II: Capping and Polyadenylation
RNA Splicing 1
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AL-RAISALMILL M. ALAWI
●The order of addition of the general transcription factors (and RNA
GENERAL TRANSCRIPTION FACTORS polymerase) to the preinitiation complex in vitro is as follows:
● Eukaryotic RNA polymerases, rely on proteins called transcription ○ TFIID (or TFIIA 1 TFIID)
factors to show them the way to their respective promoters ○ TFIIB
SUCH FACTORS ARE GROUPED INTO TWO CLASSES: ○ TFIIF 1 polymerase II
● general transcription factors ○ TFIIE
● gene-specific transcription factors (activators). ○ TFIIH. The V
● General transcription factors and the three polymerases alone ● Figure 11.2 shows the results of a footprinting study on the DA and ●
allow for only minimal transcription control, whereas Activators DAB complexes.
help cells exert exquisitely fine control over transcription. ● Reinberg and colleagues used two different reagents to cut the ●
11.1 Class II Factors protein–DNA complexes:
● The general transcription factors combine with RNA polymerase to ○ 1.) 1,10-phenanthroline (OP)-copper ion complex, which
form a preinitiation complex that is competent to initiate creates hydroxyl radicals ●
transcription as soon as nucleotides are available. ○ 2.) DNase I
● This tight binding involves the formation of an open promoter ● RNA polymerase II is a very big protein, so we would expect it to
complex in which the DNA at the transcription start site has melted cover a large stretch of DNA and leave a big footprint. ●
to allow the polymerase to read it. STRUCTURE AND FUNCTION OF TFIID ●
The Class II Preniation Complex ● TFIID is a complex protein containing a TATA-box binding protein
● Contains: polymerase II and six general transcription factors named (TBP) and 13 core TBP-associated factors (TAFs, or more
TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. specifically, TAFIIs). The T
● `Class II general transcription factors and RNA polymerase II bind ● The subscript “II” was traditionally used when the context was ●
in a specific order to the growing preinitiation complex, at least in unclear, because TBP also participates in the transcription of class I
vitro. and III genes and is associated with different TAFs (TAFIs and
● Danny Reinberg, as well as Phillip Sharp and their colleagues: TAFIIIs) in class I and III preinitiation complexes, respectively.
○ performed DNA gel mobility shift and DNase and hydroxyl ● The TATA-Box-Binding Protein (TBP) binds to the minor groove
radical footprinting experiments of the TATA box and is highly evolutionarily conserved:
● Figure 11.1a presents the results of a gel mobility shift assay ○ Yeast, fruit flies, plants, and humans have
performed by Danny Reinberg and Jack Greenblatt and their TATA-box-binding domains that are more than 80%
colleagues using TFIIA, TFIID, TFIIB, and TFIIF, as well as RNA identical in amino acid sequence.
polymerase II. ○ These domains encompass the carboxyl-terminal 180 ●
Four Distinct Preiniitiation Complexes amino acids of each protein
● Transcription factors bind to class II promoters in the following order ● Tjian’s group demonstrated the importance of the
in vitro: carboxyl-terminal 180 amino acids of TBP when they showed by
● They added TFIID and TFIIA to the DNA containing the adenovirus DNase I footprinting that a truncated form of human TBP. ●
major late promoter binds to the TATA box forming the DA complex ● How does the TBP in TFIID bind to the TATA box?
● TFIIB in addition to D and A it forms a DAB complex ● Diane Hawley and Robert Roeder, showed convincingly that the
● Next, TFIIF helps RNA polymerase bind to a region extending from TBP in TFIID binds to the minor groove of the TATA box. ●
at least position -34 to position +17, two new complexes appeared ● How does TFIID associate with the TATA box minor groove?
now it is DABPolF complex ● Nam-Hai Chua, Roeder, and Stephen Burley and colleagues TATA-
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