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P R Courtois

Publications and source records attributed to P R Courtois.

3 recordsLinked to original sources

Fast analysis of genomic homologies: primate immunodeficiency virus.

We have recently published a new probabilistic algorithm which performs genomic comparisons on a huge scale. In the present paper it was applied to immunodeficiency viral sequences extracted from international gene databanks. During global sequence analysis of human (HIV1 and HIV2) and simian viruses by means of dot-matrix representation, series of homology were obtained which permitted the definition of families of viruses overlapping the species divisions. Sequences of interest were characterized to the lexical base sentence through successive zoomings. Strain-to-strain comparison confirmed subfamily classifications and led, for example, to the identification of divergent LTR sequences. By way of example, we described the application of the algorithm to the ANT70C and MVP5180 HIV1-O viruses, for which the observed differences were shown to correspond to a deletion in the U3 region, situated between the LEF and NF-kappaB sites. It was of interest to consider these data in a tentative phylogenetic interpretation.

Algorithms↗

A probabilistic algorithm for interactive huge genome comparison.

We designed a new probabilistic algorithm, named PAGEC (probabilistic algorithm for genome comparison), which allowed a highly interactive study of long genomic strings. The comparison between two nucleic acid sequences is based on the creation of multiple index tables, which drastically reduces processing time for huge genomes, e.g. 13 min for a 4 Mb/4 Mb comparison. PAGEC lowered the need for memory when compared with other types of algorithm and took into account the low resolution of the final representation (paper or computer screen). Considering that standard printers permit a 300 d.p.i. resolution, the loss of computed information due to the probabilistic conception of the algorithm was not usually noticeable in the present study, mainly due to increased genomic sizes. Refinement was possible through an interactive zooming system, which enabled the visualization of the lexical base sequences of a considered part of both of the studied genomes. Biological examples of computation based on yeast and animal nucleic acid sequences presented in this paper reveal the flexibility of the PAGEC program, which is a valuable tool for genetic studies as it offers a solution to an important problem that will become even more important as time passes.

Algorithms↗