Engineering of ribozymes with useful activities in … Mueller.pdfEngineering of ribozymes with...
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Engineering of ribozymes with useful activities in the ancient RNA world
Sabine Müller
Ernst‐Moritz‐Arndt Universität Greifswald,
Institut für Biochemie,
Lehrstuhl für Bioorganische Chemie
DNA habitats and their RNA inhabitants, 3‐5 July 2014, Salzburg, Austria
Our “RNA world”
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Synthesis !Modified nucleosides and nucleotides
!Modified long‐mer RNAs
!DNA/RNA modifiers
!Trinucleotide synthons (gene libraries)
Engineering !Self‐processing RNAs !Twin ribozymes
!Aptazymes
!RNA aminoacylase ribozyme
Selection in vitro !Aptamers for diagnostics and therapy
!Ribozymes
Functional studies !Ribozymes
!Riboswitches
RNA
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Engineering of RNA activity
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• Aminoacylation • Signal transduction • Self‐ligation • Topology change /oligomerization • Recombination
Xu et al., ChemBioChem, 2014 Strohbach et al., Angew. Chem. Int. Ed., 2006; Electroanalysis, 2008
The hairpin ribozyme
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‐derived from Tobacco Ringspot
Virus Satellite RNA
‐positively charged co‐factors
(Mg2+) required for activity
‐bent active conformation with
contacts between loop A and
loop B
‐catalyzes the reversible
cleavage of a specific
phosphodiester bond
‐internal equlibrium is shifted
towards ligation
C AC A C U - 5'
5'- A A A G A GA
G AA
G U G A AC GC GA UG C
A GA A A C
A
CA
UU
A UA
UG
A UC G
U 3'A
Loop B
Loop A
U G
H-1 H-2H-3
H-4C G
GU
U
U U U UC C3'-
substrate strand
ribozymestrand
! smu_Salzburg_07/2014
Catalytic strategies used by the hairpin ribozyme
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! General acid‐base catalysis
! Electrostatic stabilization of the charged transition state
! Conformational effects facilitating the formation of the
in‐line geometry
OO A-1
OOPO OO
O G+1
OHO
H
OO
A-1
OOPO O
OO G+1
OHO
OO A-1
OOP
-O O
OO G+1
OHO
H
HB B
A H A
Timothy et al., RNA, 2011 smu_Salzburg_07/2014
Ligation profits from structural stabilization
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Minimal motif Three‐way junction Four‐way junction
Ligation
Cleavage
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kcleave
= 0.2 min‐1
klig = 0.4 min‐1
kcleave
= 0.5 min‐1
klig = 2.9 min‐1
Favoring cleavage/ligation by structural manipulation
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Hairpin ribozymes with stable secondary (and tertiary) structure favor ligation, while hairpin ribozymes that are less stable, however stable enough to fold into a catalytically competent structure, favor cleavage.
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Autocatalytic self‐ligation
8 Gwiazda et al., Biochimie, 2012 smu_Salzburg_07/2014
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Can we program an RNA molecule to run through a cascade of cleavage and ligation reactions and to change its topology?
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Initial purpose: making circular RNA
Pieper et al. (2007) Chem. Biol.; Petkovic & Müller (2013) FEBS Lett. smu_Salzburg_07/2014
Hairpin Ribozyme Dimerization … and Concatemerization?
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Hairpin ribozym dimers were identified previously! S. E. Butcher & J. M. Burke, 1994, Biochemistry 33, 992‐999.
C AC A C U - 5'
5'- A A A G A GA
G AA
G U G A AC GC GA UG C
A GA A A C
A
CA
UU
A UA
UG
A UC G
U 3'A
Loop B
Loop A
U G
H-1 H-2H-3
H-4C G
GU
U
U U U UC C3'-
substrate strand
ribozymestrand
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Product spectrum
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103
83 94 92
186 175
166 177
! Analysis of oligomers (Sequencing, conc. variation, 2D PAGE, exonuclease digestion)
! Imaging (Stefan Block, Mihaela Delcea, ZIK HIKE)
! Further evaluation/optimization of the system using computer‐aided prediction (Ivo
Hofacker, Christoph Flamm, Vienna University)
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Concentration dependence
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% Intensity
Concentration
RNA species
0.4 µM 2 µM 10 µM No.
linear trimer ? 1.2 2.0 4.5 e
circular dimer ? 8.2 7.3 7.0 d
circular 83mer 8.1 6.7 9.5 c
linear dimer 4.2 13.6 16.2 b
linear 83mer 78.3 70.5 62.8 a
smu_Salzburg_07/2014 Petkovic & Müller, FEBS Lett., 2013
2D gel analysis
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a 100b b c 200b d 300b
2 dimensionndb)a) 1 dimensionst
a
b
c
d
100b
200b
300b
1 2 3 a b c d
native denaturingdenaturing
smu_Salzburg_07/2014 Petkovic & Müller, FEBS Lett., 2013
Exonuclease assay
15 Petkovic & Müller, FEBS Lett., 2013
ladder 0 min 2 min
control
4 min
PDE I PDE I co co PDE I
a
e
d
c
b
cyclic
monomer
dimer
l‐83 ladder
Summary: self‐processing hairpin ribozyme variants
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… programmed self-cleavage and self-ligation for topology change ! circular species and concatemers … computer-aided design towards preferential circularization/oligomerization … external control of activity and sequence flexibility ! Technology for the synthesis of functional circular RNAs
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Two RNA cleavage reactions and two ligations Activity control by stability modulation of the twin ribozyme-substrate/product complexes Up to 53 % yield of fragment exchange
Ribozyme mediated RNA recombination
Welz et al. (2003) Angew. Chem. smu_Salzburg_07/2014
Twin ribozymes
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! Facile dissociation of the red sequence versus stable binding of the blue sequence
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Thermodynamics and kinetics of fragment exchange
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Tm = 38 °C
KD = 6.7 µM
kon = 5.2 105 M‐1 s‐1
koff = 5 s‐1
Tm = 73 °C
KD = 6.2 nM
kon = 6.7 105 M‐1 s‐1
koff = 0.01 s‐1
smu_Salzburg_07/2014 Ivanov et al., FEBS J., 2005
Twin ribozyme mediated RNA recombination
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Welz et al., Angew. Chem. Int. Ed. 2003, 42, 2424‐2427; Ivanov et al., FEBS J., 2005, 272, 4464‐4474. Balke et al., ChemMedChem,
2014, just accepted
Drude et al., Biochem. Biophys. Res. Comm., 2007, 363, 24‐29
Vauléon et al., ChemBioChem 2005, 6, 2158‐2162
45 %
20 %
5‐30%
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Hairpin ribozyme mediated recombination
21 Robert Hieronymus
functional part
functional part
functional part functional part
non‐functional part
non‐functional part
Non‐functional
RNAs
Functional ribozyme
Recombination reaction
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Summary: RNA recombination
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Twin ribozymes mediate two cleavages and two ligation events in a strictly controlled manner !fragment exchange !activity control by stability modulation of the twin ribozyme-substrate/product complexes
Hairpin ribozyme Mediates recombination of two non-functional RNAs by two cleavages and one ligation event !Generation of functional hammerhead ribozyme (self-cleavage)
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Conclusions
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• Self‐assembly and ligation • Response to external stimuli • Oligomerization and topology change • Recombination
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Greifswald
AG Bioorganische Chemie, Institut für Biochemie
Ernst‐Moritz‐Arndt Universität Greifswald
DFG, BMWi
Darko
Robert
and ….Jiacui Xu, Denise Strohbach, Sonja Petkovic….
Collaborators Vienna University
Ivo Hofacker
Christoph Flamm
Stefan Badelt
ZIK HIKE Greifswald
Mihaela Delcea
Stephan Block
Thanks to All!