Control of Gene Expression
Chapter 16
Genes and Development
Proteins can determine the
DNA sequence by binding
the major groove of DNA.
Proteins binding the minor
groove cannot determine
the exact sequence of bases.
Prokaryotic gene regulation
Lac Operon
Prokaryotic gene regulation
Trp Operon
Biosynthesis of the amino acid typtophan
Therefore, the regulation is the opposite of the lac operon.
Eukaryotic gene regulation
Enhancer (DNA sequence)
Looping
Activator (protein)
ATP
ADP + Pi
ATP -dependent
remodeling factor
1. Nucleosome sliding
2. Remodeled nucleosome
3. Nucleosome displacement
4. Histone replacement
RNA Polymerase II
microRNA gene
Pri-microRNA
Nucleus
Pre-microRNA
Drosha
Exportin 5
Cytoplasm
Dicer
Mature miRNA
RISC
mRNA
RISC
mRNA cleavage
mRNA
RISC
Inhibition of translation
RISC
Exogenous dsRNA, transposon, virus
Repeated cutting
by dicer
siRNAs
siRNA
in RISC
Ago
+
RISC
mRNA
Cleavage of target mRNA
Ago
RISC
RNA polymerase II
DNA
3´
5´
Primary RNA transcript
1. Initiation of
transcription
Most control of
gene expression
is achieved
by regulating
the frequency
of transcription
initiation.
Cut
intron
5´ cap
Exons
Introns
3´ poly-A tail
Mature RNA transcipt
2. RNA splicing
Gene expression
can be controlled
by altering the
rate of splicing in
eukaryotes.
Alternative splicing
can produce
multiple mRNAs
from one gene.
Large
subunit
3´ poly-A tail
Nuclear
pore
mRNA
Small
subunit
3´
5´
3. Passage through
the nuclear
membrane
Gene expression
can be regulated
by controlling
access to or
efficiency of
5´ cap
transport channels.
4. Protein synthesis
Many proteins take
part in the
translation process,
and regulation
of the availability
of any of them alters
the rate of gene
expression by
speeding or slowing
protein synthesis.
P
P
Completed
polypeptide
chain
6. Posttranslational
modification
Phosphorylation
or other chemical
modifications can
alter the activity
of a protein after
it is produced.
RISC
5. RNA interference
Gene expression
is regulated by
small RNAs. Protein
complexes
containing siRNA
and miRNA target
specific mRNAs for
destruction or inhibit
their translation.
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