MOTIVATION: Enhancing expression levels of a target protein is an important goal in synthetic biology. A widely used strategy is to integrate multiple copies of genes encoding a target protein into a host organism genome. Integrating highly similar sequences, however, can induce homologous recombination between them, resulting in the ultimate reduction of the number of integrated genes. RESULTS: We propose a method for designing multiple protein-coding sequences (i.e. CDSs) that are unlikely to induce homologous recombination, while encoding the same protein. The method, which is based on multi-objective genetic algorithm, is intended to design a set of CDSs whose nucleotide sequences are as different as possible and whose codon usage frequencies are as highly adapted as possible to the host organism. We show that our method not only successfully designs a set of intended CDSs, but also provides insight into the trade-off between nucleotide differences among gene copies and codon usage frequencies. AVAILABILITY AND IMPLEMENTATION: Our method, named Tandem Designer, is available as a web-based application at http://tandem.trahed.jp/tandem/ . CONTACT: : [email protected] or [email protected]. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

MOTIVATION: An important problem in synthetic biology is to design a nucleotide sequence of an mRNA that confers a desirable expression level of a target protein. The secondary structure of protein-coding sequences (CDSs) is one potential factor that could have both positive and negative effects on protein production. To elucidate the role of secondary structure in CDSs, algorithms for manipulating secondary structure should be developed. RESULTS: We developed an algorithm for designing a CDS with the most stable secondary structure among all possible ones translated into the same protein, and implemented it as the program CDSfold. The algorithm runs the Zuker algorithm under the constraint of a given amino acid sequence. The time and space complexity is O(L(3)) and O(L(2)), respectively, where L is the length of the CDS to be designed. Although our algorithm is slower than the original Zuker algorithm, it could design a relatively long (2.7-kb) CDS in approximately 1 h. AVAILABILITY AND IMPLEMENTATION: The CDSfold program is freely available for non-commercial users as stand-alone and web-based software from http://cdsfold.trahed.jp/cdsfold/ CONTACTS: [email protected] or [email protected] SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.