Influence of
tandemly repeated sequences on genome dynamics: study of the molecular evolution
of the Saccharomyces cerevisiae DUP240 family.
Bénédicte Wirth,
Laurence Despons, Véronique Leh-Louis, Serge Potier, Jean-Luc Souciet
FRE 2326 ULP/CNRS, Institut de Botanique, 28, rue Goethe, Strasbourg, 67083,
France (wirth@gem.u-strasbg.fr)
The Saccharomyces
cerevisiae
S288C DUP240
ORFs constitute a large multigenic family with 10 members which encode putative
proteins of about 240 amino acids of unknown function. The DUP240 ORFs are located on four
chromosomes and most paralogs are arranged as tandem repeats, five ORFs are
tandemly repeated on chromosome I and two on chromosome VII. A comparative
analysis of these two regions realized in 15 S. cerevisiae strains coming from
various environments revealed an important polymorphism in the DUP240 ORFs sequences and their
organization. The nucleotidic sequence alterations observed are generally due
to silent or non synonymous mutations, suggesting that these putative proteins
indeed have a function in the yeast biological cycle. We demonstrated a huge polymorphism
in the organization of the tandem repeats, since the DUP240 ORFs number and order
change between strains. Moreover new DUP240 paralogs were
identified. In addition the reshaping events observed seem to be specific to
the DUP240
ORFs, since the tandem adjacent regions are conserved in all the 15 strains.
The intra- and interchromosomal rearrangements characterized at the DUP240 loci probably involved
various molecular mechanisms such as homologous recombination, non-homologous
DNA end-joining, gene conversion and duplication of ORFs units. The combination
of such mechanisms may give rise to new DUP240 paralogs. So the
tandemly repeated DUP240 ORFs seem to be sites of gene birth and death.