REGULATION OF GENE EXPRESSION

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REGULATION OF GENE EXPRESSION
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TRANSCRIPTIONAL REGULATION
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NEGATIVE REGULATION OF TRANSCRIPTION
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PUTTING IT ALL TOGETHER
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Q Is it relevant that the lacI gene is adjacent
to the lac operon?
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NEGATIVE REGULATION
REPRESSIBLE TRANSCRIPTION
Active repressor
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THE trp OPERON
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Positive Regulation
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Transcriptional Activator
Enhancer
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Building more complex genetic switches
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POST-TRANSCRIPTION INITIATION GENE REGULATION
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DsrA acts as an Anti-antisense RNA, allowing high
level RpoS translation
Low level translation
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Both RprA and DsrA can interact with the RpoS
Leader to stimulate translation
DsrA
5--ACACAUCA GAUUUCCUGGUGUAACGAAUUUUUUAAGUGCUUCUUG
--3
rpoS
?
?
CCCAAAUGCCUAAAGGGGAACAUUGCUUAAAGUUUUACGUUCGCA--5
63 nt
rpoS
Translation high
GGG U ACGGGU CC CCUU
A C A G A AUG
G A
G
G
U A
RprA
A A
G A
G C
5--UAAGCAUGGAAAUCCCCU AACGAAUUGCUGUGUGUA--3

rpoS
?
CCCAAAUGCCUAAAGGGGAACAUUGCUUAAAGUUUUACGUUCGCA--5
63 nt
rpoS
Translation high
GGG U ACGGGU CC CCUU
A C A G A AUG
G A
G
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Why use multiple RNAs to regulate RpoS?

• DsrA and RprA are synthesized in response to
  different signals.
• One small RNA can simultaneously regulate
  multiple targets, integrating different
  regulatory networks.

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Multiple small RNAs allow multiple inputs
into RpoS Translation
Other sRNAs
Cell surface stress
RprA
DsrA
Low temperature
RpoS translation
Hns translation
Other targets?
Other targets?
Oxidative stress
OxyS
Other targets?
FhlA translation
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GLOBAL MECHANISMS OF REGULATING TRANSCRIPTION
DNA methylation 5 CpG 3
Q Has the sequence of the DNA changed?