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9.3
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1The mechanisms that regulate transcription initiation and
elongation by RNA polymerase [blank_start]II[blank_end] have been studied extensively
because this polymerase is the one that transcribes
mRNAs.- AII
2Today the transcription start site for a newly characterized
mRNA is generally determined simply by identifying
the DNA sequence encoding the 3′-capped nucleotide of the
encoded mRNA.- ATrue
- BFalse
3Several different types of DNA sequences can function as
[blank_start]promoters[blank_end] for RNA polymerase II- Apromoters
4Several different types of DNA sequences can function as
promoters for RNA polymerase II, telling the polymerase
where to initiate transcription of an RNA complementary
to the template strand of a double-stranded DNA molecule.
These sequences include [blank_start]TATA[blank_end] boxes, [blank_start]initiators[blank_end], and [blank_start]CpG[blank_end]
islands.- ATATA
- Binitiators
- CCpG
5In all these highly transcribed
genes, a conserved sequence called the TATA box was found
about 26–31 bp upstream of the transcription start site
(Figure 9-16). Mutagenesis studies have shown that a singlebase
change in this nucleotide sequence drastically [blank_start]decreases[blank_end] in vitro transcription of the gene adjacent to it.- Adecreases
6If the base pairs between the TATA box and the normal transcription
start site are deleted, transcription begins at the same point regardless.- ATrue
- BFalse
7In contrast to the conserved TATA box sequence, however,
only an extremely degenerate initiator consensus sequence
has been defined- ATrue
- BFalse
8CG-rich sequences are bound by histone octamers more
[blank_start]weakly[blank_end] than CG-poor sequences because [blank_start]more[blank_end] energy is required
to bend them into the small-diameter loops required
to wrap around the histone octamer forming a [blank_start]nucleosome[blank_end]
(see Figure 8-24). As a consequence, CpG islands coincide
with nucleosome-[blank_start]free[blank_end] regions of DNA.- Aweakly
- Bmore
- Cnucleosome
- Dfree
9a current hypothesis
is that the general transcription factors discussed in the
next section can bind to them because CpG islands [blank_start]exclude[blank_end]
nucleosomes.- Aexclude
- Binclude
10Another remarkable feature of CpG islands is that transcription
from these elements is initiated in both directions,
even though only transcription of the sense strand yields an
mRNA.- ATrue
- BFalse
11Initiation of transcription by RNA polymerase II requires
several initiation factors.- ATrue
- BFalse
12Initiation Factors: They are called [blank_start]general transcriptionfactors[blank_end] because they are required at most, if not all,
promoters of genes transcribed by RNA polymerase [blank_start]II[blank_end].- Ageneral transcriptionfactors
- BII
13These factors that regulate
elongation in the promoter-proximal region provide a
mechanism for controlling gene transcription in addition
to the regulation of transcription initiation. This overall
strategy for regulating transcription at both the [blank_start]initiation[blank_end]
and [blank_start]elongation[blank_end] steps in the promoter-proximal region is
similar to the regulation of the trp operon in E. coli (see
Figure 9-7), although the molecular mechanisms involved
are distinct.- Ainitiation
- Belongation
14Three principal types of promoter sequences have been
identified in eukaryotic DNA. The [blank_start]TATA box[blank_end] is prevalent
in highly transcribed genes. [blank_start]Initiator[blank_end] promoters are found
in some genes, and [blank_start]CpG islands[blank_end], the promoters for about
70 percent of protein-coding genes in vertebrates, are characteristic
of genes transcribed at a [blank_start]low[blank_end] rate.- ATATA box
- BInitiator
- CCpG islands
- Dlow
15Transcription of protein-coding genes by Pol II is initiated
by sequential binding of the following in the indicated order:
[blank_start]TFIID[blank_end], which contains the TBP subunit that binds to TATA
box DNA; [blank_start]TFIIA[blank_end] and [blank_start]TFIIB[blank_end]; a complex of Pol II and TFIIF;
TFIIE; and finally, [blank_start]TFIIH[blank_end] (see Figure 9-19).- ATFIID
- BTFIIA
- CTFIIB
- DTFIIH
16The helicase activity of a TFIIH subunit helps to separate
the DNA strands at the transcription start site in most promoters,
a process that requires hydrolysis of ATP. As Pol II
begins transcribing away from the start site, its [blank_start]CTD[blank_end] is phosphorylated
on [blank_start]serine 5[blank_end] by the [blank_start]TFIIH[blank_end] kinase domain.- ACTD
- Bserine 5
- CTFIIH
17In metazoans, [blank_start]NELF[blank_end] and [blank_start]DSIF[blank_end] associate with Pol II after
initiation, inhibiting elongation fewer than 100 bp from the
transcription start site. Inhibition of elongation is relieved
when [blank_start]cyclin T–CDK9[blank_end] (also called P-TEFb) associates with
the [blank_start]elongation complex[blank_end] and CDK9 [blank_start]phosphorylates[blank_end] subunits
of NELF, DSIF, and serine 2 of the Pol II CTD.- ANELF
- BDSIF
- Ccyclin T–CDK9
- Delongation complex
- Ephosphorylates
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- Advanced Cell Biology I (Unit 1) Quiz on 9.3, created by Brooks Johnson on 01/06/2020.
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- Brooks Johnson
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