Growing Trees on the Right Compost

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Growing Trees on the Right Compost

• Cédric Notredame
• Comparative Bioinformatics Group
• Bioinformatics and Genomics Program

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Manguel M, Samaniego F.J., Abraham Walds Work
on Aircraft Suvivability, J. American
Statistical Association. 79, 259-270, (1984)
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What s in a Multiple Sequence Alignment
Evolution Inertia Common Ancestry Shows up In
the sequences
Selection Important Features Are Preserved
Functional Constraint Same Function Same
Sequence Convergence
Phylogenetic Footprint, Evolutionary Trace
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Why So Much Interest For Multiple Alignments ?
Extrapolation
Structure Prediction
Motifs/Patterns
SNP Analysis
Profiles
Regulatory Elements
Phylogeny
Reactivity Analysis
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Whats in a Multiple Alignment ?

• The MSA contains what you put inside
• Structural Similarity
• Evolutive Similarity
• Sequence Similarity
• You can view your MSA as
• A record of evolution
• A summary of a protein family
• A collection of experiments made for you by
  Nature

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Producing The Right Alignment

• Multiple Sequence Alignments Influence
  Phylogenetic Trees
• Choice of Method is not Neutral
• Different Methods
• Different Alignments
• Different Trees
• Using The Right Models insures Producing the
  right Tree

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Model Based Alignments vs Naïve Alignments

• Naïve Alignment
• Lexicographic Alignment
• Maximizing the number of identities
• At best using a substitution matrix
• Model Based Alignments
• Using a model
• Protein structure information
• RNA Structure information
• Combining/Confronting Modeling methods
• Template based Alignments
• Model based Alignments through the use of
  Templates

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T-Coffee and Model Based Alignments

• T-Coffee Algorithm
• Expresso Aligning Protein Structures
• R-Coffee Aligning RNA structures
• M-Coffee Combining methods

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T-Coffee An extension of the progressive
Alignment Algorithm
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T-Coffee and Concistency
SeqA GARFIELD THE LAST FAT CAT
SeqB GARFIELD THE FAST CAT
SeqC GARFIELD THE VERY FAST CAT
SeqD THE FAT CAT
SeqA GARFIELD THE LAST FA-T CAT SeqB GARFIELD THE
FAST CA-T --- SeqC GARFIELD THE VERY FAST
CAT SeqD -------- THE ---- FA-T CAT
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T-Coffee and Concistency
SeqA GARFIELD THE LAST FAT CAT Prim. Weight
88 SeqB GARFIELD THE FAST CAT --- SeqA GARFIELD
THE LAST FA-T CAT Prim. Weight 77 SeqC
GARFIELD THE VERY FAST CAT SeqA GARFIELD THE
LAST FAT CAT Prim. Weight 100 SeqD --------
THE ---- FAT CAT SeqB GARFIELD THE ---- FAST CAT
Prim. Weight 100 SeqC GARFIELD THE VERY FAST
CAT SeqC GARFIELD THE VERY FAST CAT Prim.
Weight 100 SeqD -------- THE ---- FA-T CAT
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T-Coffee and Concistency
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T-Coffee and Concistency
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T-Coffee and Concistency
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T-Coffee and Concistency
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T-Coffee and Concistency
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T-Coffee and Concistency
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When Sequences Are not Enough3D-Coffee and
Expresso
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3D-Coffee Combining Sequences and Structures
Within Multiple Sequence Alignments
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3D-Coffee Combining Sequences and Structures
Within Multiple Sequence Alignments
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Expresso Finding the Right Structure
Sources
BLAST
BLAST
SAP
Templates
Templates
Template Alignment
Source Template Alignment
Library
Remove Templates
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3D-Coffee Combining Sequences and Structures
Within Multiple Sequence Alignments
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Incorporating RNA Information Within the T-Coffee
Algorithm
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ncRNAs Can Evolve Rapidly
CCAGGCAAGACGGGACGAGAGTTGCCTGG CCTCCGTTCAGAGGTGCATA
GAACGGAGG -------------------
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R-Coffee Modifying T-Coffee at the Right Place

• Incorporation of Secondary Structure information
  within the Library
• Two Extra Components for the T-Coffee Scoring
  Scheme
• A new Library
• A new Scoring Scheme

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R-Coffee Extension
TC Library
G
C
G G Score X C C Score Y
G
C
G
C
G
C

• Goal Embedding RNA Structures Within The
  T-Coffee Libraries
• The R-extension can be added on the top of any
  existing method.

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R-Coffee Structural Aligners
Method Avg Braliscore Net Improv. direct
T R T R -----------------------------------
------------------------ Stemloc 0.62 0.75 0.76
104 113Mlocarna 0.66 0.69 0.71
101 133Murlet 0.73 0.70 0.72
-132 -73Pmcomp 0.73 0.73 0.73
142 145T-Lara 0.74 0.74 0.69 -36
-8 Foldalign 0.75 0.77 0.77 72
73 -----------------------------------------------
------------ Dyalign --- 0.63 0.62
--- --- Consan --- 0.79 0.79
--- --- ------------------------------------------
----------------- Improvement R-Coffee wins -
R-Coffee looses over 170 test sets
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R-Coffee Regular Aligners
Method Avg Braliscore Net Improv. direct
T R T R -----------------------------------
------------------------ Poa 0.62 0.65 0.70
48 154Pcma 0.62 0.64 0.67 34 120Prrn 0.64
0.61 0.66 -63 45ClustalW 0.65 0.65 0.69 -7
83Mafft_fftnts 0.68 0.68 0.72 17
68ProbConsRNA 0.69 0.67 0.71 -49
39Muscle 0.69 0.69 0.73 -17
42Mafft_ginsi 0.70 0.68 0.72 -49
39 -----------------------------------------------
------------
Improvement R-Coffee wins - R-Coffee looses
over 388 test sets
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Choosing the right modeling methodM-Coffee
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Combining Many MSAs into ONE
ClustalW
MAFFT
T-Coffee
MUSCLE
???????
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Comparing Methods
MAFFT
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Where to Trust Your Alignments
Most Methods Disagree
Most Methods Agree
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What To Do Without Structures
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Conclusion

• Model Based Alignments Give the best Accuracy
• Template based alignment is a very efficient way
  to turn Naïve aligners into model based aligners
• Sequence Alignments are not necessarily reliable
  over their entire lengths

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www.tcoffee.org

• Fabrice Armougom (CNRS, FR)
• Sebastien Moretti (CNRS, FR)
• Olivier Poirot (CNRS, FR)
• Frederic Reinier (CRS4, IT)
• Karsten Suhre (CNRS, FR)
• Vladimir Saudek (Sanofi-Aventis, FR)
• Des Higgins (UCD, IE)
• Orla OSullivan (UCD, IE)
• Iain Wallace (UCD, IE)
• Victor Jongeneel (SIB/VitalIT, CH)
• Bruno Nyfler (VitalIT, CH)
• Roger Hersch (EPFL, CH)
• Pierre Dumas (EPFL, CH)
• Basile Schaeli (EPFL, CH)

www.tcoffee.org cedric.notredame_at_europe.com
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www.tcoffee.org
www.tcoffee.org cedric.notredame_at_europe.com
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Building and Using Models
35.67 Angstrom
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Computing the Correct Alignment is a Complicated
Problem
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Stochastic Optimization
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Stochastic Optimization

• Exploration of Complex Optimization Problems With
  Multiple Constraints
• Genomic Alignments
• RNA Alignments
• Generation of Population of Suboptimal Solutions
• Qualityf( optimality )
• Specification of Concistency Objective Function
  of T-Coffee

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Three Types of Algorithms

• Progressive ClustalW
• Iterative Muscle
• Concistency Based T-Coffee and Probcons

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T-Coffee and Concistency

• Each Library Line is a Soft Constraint (a wish)
• You cant satisfy them all
• You must satisfy as many as possible (The easy
  ones)

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Concistency Based Algorithms T-Coffee

• Gotoh (1990)
• Iterative strategy using consistency
• Martin Vingron (1991)
• Dot Matrices Multiplications
• Accurate but too stringeant
• Dialign (1996, Morgenstern)
• Concistency
• Agglomerative Assembly
• T-Coffee (2000, Notredame)
• Concistency
• Progressive algorithm

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How Good Is My Method ?
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Structures Vs Sequences
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Validation Using BaliBase
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Too Many Methods for ONE AlignmentM-Coffee
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Estimating the Accuracy of your MSA
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What To Do Without Structures
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3D-Coffee Combining Sequences and Structures
Within Multiple Sequence Alignments
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Expresso Finding the Right Structure
Why Not Using Structure Based Alignments
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Template Based Multiple Sequence Alignments
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Template Based Multiple Sequence Alignments
Sources
-Structure -Profile -
Template Aligner
-Structure -Profile -
Templates
Templates
Template Alignment
Source Template Alignment
Library
Remove Templates
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Method Score Templates Prefab Homstrad
-------------------------------------------------
------------- ClustalW Matrix ---- 61.80 ----
Kalign Matrix ---- 63.00 ---- MUSCLE Matrix
---- 68.00 45.0 --------------------------------
------------------------------ T-Coffee Consisten
cy ---- 69.97 44.0 ProbCons Consistency ---- 7
0.54 ---- Mafft Consistency ---- 72.20 ---- M-
Coffee Consistency ---- 72.91 ---- MUMMALS Consi
stency ---- 73.10 ---- -------------------------
------------------------------------- Clustal-db
Matrix Profiles ---- ---- PRALINE Matrix Profi
les ---- 50.2 PROMALS Consistency Profiles 79.00
---- SPEM Matrix Profiles 77.00 ---- ---------
--------------------------------------------------
--- EXPRESSO Consistency Structures ---- 71.9
T-Lara Consistency Structures ---- ---- ------
--------------------------------------------------
------ Table 1. Summary of all the methods
described in the review. Validation figures were
compiled from several sources, and selected for
the compatibility. Prefab refers to some
validation made on Prefab Version 3. The HOMSTRAD
validation was made on datasets having less than
30 identity. The source of each figure is
indicated by a reference. The EXPRESSO figure
comes from a slightly more demanding subset of
HOMSTRAD (HOM39) made of sequences less than 25
identical.
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Improving The Evaluation
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How Do We Perform In The Twilight Zone?

• Concistency Based Methods Have an Edge
• Hard to tell Methods Apart
• Sequence Alignment is NOT solved

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More Than Structure based Alignments

• Structural Correctness Is Only the Easy Side of
  the Coin.
• In practice MSA are intermediate models used to
  generate other models

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Conclusion

• Template based Multiple Sequence Alignments
• Projecting any relevant information onto the
  sequences
• Using this Information
• Need for new evaluation procedures
• Functional Analysis
• Phylogenetic Analysis
• Homology Search (Profiles)
• Homology Modelling
• Integrating data ? Making sure your bits of data
  can fight with one another

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Turning Data into Models

• Data
• Columbus, considered that the landmass occupied
  225, leaving only 135 of water (Marinus of
  Tyre, 70 AD).
• Columbus believed that 1 represented only 56
  miles (Alfraganus, XIth century)
• He knew there was an island named Japan off the
  cost of China
• Model
• Circumference of the Earth as 25,255 km at most,
• Canary Island to Japan 3,700 km (Reality
  12,000 km.)

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The More Structures The Merrier
Average Improvement over T-Coffee
Struc/Seq Ratio
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The Right Mixt of Methods
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3D-Coffee Combining Sequences and Structures
Within Multiple Sequence Alignments
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Applications
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Looking-Up The DNA Behind The Sequences PROTOGENE
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SAR Analysis

• Correlate Alignment Variations with Reactivity
• Application to the Human Kinome
• Collaboration with Sanofi-Aventis
• Main Issue
• Training problem ? Proper Benchmarking

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ncRNA Multiple Alignments with R-Coffee

• Laundering the Genome Dark Matter
• Cédric Notredame
• Comparative Bioinformatics Group
• Bioinformatics and Genomics Program

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No Plane Today
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ncRNAs Comparison

• And ENCODE said
• nearly the entire genome may be represented in
  primary transcripts that extensively overlap and
  include many non-protein-coding regions
• Who Are They?
• tRNA, rRNA, snoRNAs,
• microRNAs, siRNAs
• piRNAs
• long ncRNAs (Xist, Evf, Air, CTN, PINK)
• How Many of them
• Open question
• 30.000 is a common guess
• Harder to detect than proteins
• .

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ncRNAs can have different sequences and Similar
Structures
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ncRNAs are Difficult to Align

• Same Structure ?Low Sequence Identity
• Small Alphabet, Short Sequences ? Alignments
  often Non-Significant

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Obtaining the Structure of a ncRNA is difficult

• Hard to Align The Sequences Without the Structure
• Hard to Predict the Structures Without an
  Alignment

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The Holy Grail of RNA ComparisonSankoff
Algorithm
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The Holy Grail of RNA ComparisonSankoff
Algorithm

• Simultaneous Folding and Alignment
• Time Complexity O(L2n)
• Space Complexity O(L3n)
• In Practice, for Two Sequences
• 50 nucleotides 1 min. 6 M.
• 100 nucleotides 16 min. 256 M.
• 200 nucleotides 4 hours 4 G.
• 400 nucleotides 3 days 3 T.
• Forget about
• Multiple sequence alignments
• Database searches

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The next best Thing Consan

• Consan Sankoff a few constraints
• Use of Stochastic Context Free Grammars
• Tree-shaped HMMs
• Made sparse with constraints
• The constraints are derived from the most
  confident positions of the alignment
• Equivalent of Banded DP

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Going Multiple.

• Structural Aligners

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Game Rules

• Using Structural Predictions
• Produces better alignments
• Is Computationally expensive
• Use as much structural information as possible
  while doing as little computation as possible

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Adapting T-Coffee To RNA Alignments
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T-Coffee and Concistency
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T-Coffee and Concistency
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T-Coffee and Concistency
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T-Coffee and Concistency
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Consistency Conflicts and Information
X
X
Z
Z
Y
Y
W
Z
Z
W
Y is unhappy
X is unhappy
Partly Consistent ? Less Reliable
Fully Consistent ? More Reliable
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R-Coffee Scoring Scheme
R-Score (CC)MAX(TC-Score(CC), TC-Score (GG))
G
C
G
C
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Validating R-Coffee
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RNA Alignments are harder to validate than
Protein Alignments

• Protein Alignments ? Use of Structure based
  Reference Alignments
• RNA Alignments ?No Real structure based reference
  alignments
• The structures are mostly predicted from
  sequences
• Circularity

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BraliBase and the BraliScore

• Database of Reference Alignments
• 388 multiple sequence alignments.
• Evenly distributed between 35 and 95 percent
  average sequence identity
• Contain 5 sequences selected from the RNA family
  database Rfam
• The reference alignment is based on a SCFG model
  based on the full Rfam seed dataset (100
  sequences).

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BraliBase SPS Score
Number of Identically Aligned Pairs
RFam MSA
SPS
Number of Aligned Pairs
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BraliBase SCI Score
R N A p f o l d
Covariance
((()))((..)) DG Seq1
((()))((..)) DG Seq2
((()))((..)) DG Seq3
((()))((..)) DG Seq4
((()))((..)) DG Seq5
((()))((..)) DG Seq6
RNAlifold
Average DG Seq X Cov
SCI
((()))((..)) ALN DG
DG ALN
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BRaliScore

• Braliscore SCISPS

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RM-Coffee Regular Aligners
Method Avg Braliscore Net Improv. direct
T R T R -----------------------------------
------------------------ Poa 0.62 0.65 0.70
48 154Pcma 0.62 0.64 0.67 34 120Prrn 0.64
0.61 0.66 -63 45ClustalW 0.65 0.65 0.69 -7
83Mafft_fftnts 0.68 0.68 0.72 17
68ProbConsRNA 0.69 0.67 0.71 -49
39Muscle 0.69 0.69 0.73 -17
42Mafft_ginsi 0.70 0.68 0.72 -49
39 -----------------------------------------------
------------ RM-Coffee4 0.71 / 0.74 / 84
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How Best is the Best.
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Range of Performances
Effect of Compensated Mutations
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Conclusion/Future Directions

• T-Coffee/Consan is currently the best MSA
  protocol for ncRNAs
• Testing how important is the accuracy of the
  secondary structure prediction
• Going deeper into Sankoffs territory predicting
  and aligning simultaneously

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Credits and Web Servers

• Andreas Wilm
• Des Higgins
• Sebastien Moretti
• Ioannis Xenarios
• Cedric Notredame
• CGR, SIB, UCD

www.tcoffee.org cedric.notredame_at_europe.com
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