Phage Strategies

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Phage Strategies

• Timothy G. Standish, Ph. D.

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The l Regulatory Region
N utilization right
Terminator right
N utilization left
Terminator left
Repressor
Positive regulator
Anti-repressor
Anti-terminator
Positive regulator
c clear referring to the clear plaques
resulting from functional c genes
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The l Regulatory Region
Promoter Represser Establish-ment
Promoter/ Operator right
Promoter/ Operator left
Promoter Represser Maintainence
Repressor
Positive regulator
Anti-repressor
Anti-terminator
Positive regulator
c clear referring to the clear plaques
resulting from functional c genes
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The l Regulatory RegionInfection
Host RNA Polymerase recognizes PL and PR and
begins transcription of the N and cro proteins
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The l Regulatory RegionInfection -
Establishment of Lysogeny
Host RNA Polymerase recognizes PL and PR and
begins transcription of the N and cro proteins
As they are the very first genes to be expressed,
N and cro are called immediate early genes.
cro
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The l Regulatory RegionInfection -
Establishment of Lysogeny
pN binds to nut sites allowing transcription
through tR1 and tL
cro
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The l Regulatory RegionInfection -
Establishment of Lysogeny
pN binds to nut sites allowing transcription
through tR1 and tL
cro
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The l Regulatory RegionInfection -
Establishment of Lysogeny
The cII and cIII proteins are produced. In vivo a
protein called HflA rapidly breaks down cII
unless it is combined with cIII. cII up
regulates transcription from PRE.
cro
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The l Regulatory RegionInfection -
Establishment of Lysogeny
Transcription from PRE makes mRNA complementary
to the cro mRNA thus inhibiting cro translation
cro
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The l Regulatory RegionInfection -
Establishment of Lysogeny
The transcript from PRE provides a 3
untranslated region with an efficient ribosome
binding site before the start of the cI gene,
thus cI repressor is efficiently produced.
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The l Regulatory RegionInfection -
Establishment of Lysogeny
The repressor gene product of cI binds to OR and
OL preventing transcription from PR and PL.
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The l Regulatory RegionInfection -
Establishment of Lysogeny
The repressor up-regulates expression from PRM
maintaining repressor production and preventing
expression of any other proteins and establishing
lysogeny.
cI
cI
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The l Repressor Protein

• Repressor protein has two functional domains
• An amino acid (residue) 1-92 N-terminal DNA
  binding domain which binds to OR and OL
• A C-terminal protein binding domain essential for
  dimerization running from amino acids 132-236
• A 40 residue connector runs Between the two
  domains

Repressor only binds DNA efficiently when it is a
dimer
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The l Regulatory RegionInfection -
Establishment of The Lytic Cycle
Host RNA Polymerase recognizes PL and PR and
begins transcription of the N and cro proteins
As they are the very first genes to be expressed,
N and cro are called immediate early genes.
cro
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The l Regulatory RegionInfection -
Establishment of The Lytic Cycle
Host RNA Polymerase recognizes PL and PR and
begins transcription of the N and cro proteins
cI
cro
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The l Regulatory RegionInfection -
Establishment of The Lytic Cycle
Host RNA Polymerase recognizes PL and PR and
begins transcription of the N and cro proteins
5CATACGTTAAATCTATCACCGCAAGGGATAAATATCTAACACCGTGC
GTGTTGACTATTTTACCTCTGGCGGTGATAATGGTTGCATG3 3ATG
TGCAATTTAGATAGTGGCGTTCCCTATTTATAGATTGTGGCACGCACAA
CTGATAAAATGGAGACCGCCACTATTACCAACGTAC5
cI
cro
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The l Regulatory RegionInfection -
Establishment of The Lytic Cycle
5CATACGTTAAATCTATCACCGCAAGGGATAAATATCTAACACCGTGC
GTGTTGACTATTTTACCTCTGGCGGTGATAATGGTTGCATG3 3ATG
TGCAATTTAGATAGTGGCGTTCCCTATTTATAGATTGTGGCACGCACAA
CTGATAAAATGGAGACCGCCACTATTACCAACGTAC5
cI
cro
The N terminus of the repressor binds to OR1 and
2 with high affinity
The N terminus of the repressor binds to OR1 and
2 with high affinity
The N terminus of the repressor binds to OR1 and
2 with high affinity
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The l Regulatory RegionInfection -
Establishment of The Lytic Cycle
Host RNA Polymerase recognizes PL and PR and
begins transcription of the N and cro proteins
5CATACGTTAAATCTATCACCGCAAGGGATAAATATCTAACACCGTGC
GTGTTGACTATTTTACCTCTGGCGGTGATAATGGTTGCATG3 3ATG
TGCAATTTAGATAGTGGCGTTCCCTATTTATAGATTGTGGCACGCACAA
CTGATAAAATGGAGACCGCCACTATTACCAACGTAC5
cI
cro
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The l Regulatory RegionInfection -
Establishment of The Lytic Cycle
OR3 CTATCACCGCAAGGGATAA OR2 CTAACACCGTGCGTGTTGA OR
1 TTACCTCTGGCGGTGATAA OL3 TAACCATCTGCGGTGATAA OL2
TTATCTCTGGCGGTGTTGA OL1 ATACCACTGGCGGTGATAC
OR3 CTATCACCGCAAGGGATAA OR2 CTAACACCGTGCGTGTTGA OR
1 TTACCTCTGGCGGTGATAA OL3 TAACCATCTGCGGTGATAA OL2
TTATCTCTGGCGGTGTTGA OL1 ATACCACTGGCGGTGATAC CON -
TAYCWCYGGCGGTGWTR-
Right and left operator sites share a common
consensus sequence.
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(No Transcript)