Approximation Algorithms for Optimal RNA Secondary Structures Common to Multiple Sequences

Takeyuki TAMURA
Tatsuya AKUTSU

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E90-A    No.5    pp.917-923
Publication Date: 2007/05/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e90-a.5.917
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Discrete Mathematics and Its Applications)
Category: 
Keyword: 
computational biology,  RNA secondary structure prediction,  approximation algorithms,  

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Summary: 
It is well known that a basic version (i.e., maximizing the number of base-pairs) of the RNA secondary structure prediction problem can be solved in O(n3) time by using simple dynamic programming procedures. For this problem, an O(n3(log log n)1/2/(log n)1/2) time exact algorithm and an O(n2.776+(1/ε)O(1)) time approximation algorithm which has guaranteed approximation ratio 1-ε for any positive constant ε are also known. Moreover, when two RNA sequences are given, there is an O(n6) time exact algorithm which can optimize structure and alignments. In this paper, we show an O(n5) time approximation algorithm for optimizing structure and alignments of two RNA sequences with assuming that the optimal number of base-pairs is more than O(n0.75). We also show that the problem to optimize structure and alignments for given N sequences is NP-hard and introduce a constant-factor approximation algorithm.


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