Research Groups

Yeast Molecular Genetics

Research Interests and Description

Research Interests

Genome dynamics in yeast: DNA integration, aneuploidy and chromosomal translocation.

Description of Research

Our Group has pioneered the field of chromosomal translocations induced in vivo, by implementing the bridge-induced translocation (BIT) methodology to construct different mutants carrying ad hoc chromosome translocations at pre-defined DNA points, using the yeast S. cerevisiae as a cellular eukaryotic model system (Tosato et al. 2005). The BIT system pre-empties the question whether the translocation caused the cellular defects or was the result of them, establishing a clear temporal order. A first, most important conclusion deriving from our observations is that a single translocation event leads to a successive cascade of molecular events eventually ensuing in genomic instability. From an evolutionary point of view, that is probably why GCRs (gross chromosomal rearrangements) formation is normally suppressed by many factors, as it is usually strongly deleterious to the cells. These first results are important for the manipulation and stable maintenance of Yeast Artificial Chromosomes (YACs) the use of which is at the basis of modern genome manipulation technologies like recombineering (Bruschi et al. 2006). A noticeable observation is that the genomic modifications following the primary event of translocation seem to become a continuous phenomenon up to the number of cell divisions that usually coincides with cell senescence, providing a thought-provoking indication of one of the molecular mechanisms for evolution in being (Laun et al., 2007). Chromosome translocation is generating severe alterations at both genomic and transcriptomic level when it happens between two heterologous chromosomes (Nikitin et al., 2008). However, this effect is greatly diminished when BIT happens between two homologous chromosomes, although with the important result that, in the DNA integration process, a loss of heterozygosity (LOH) is generated on one of the recombinant chromosomes, preventing duplication of the region between the two recombining loci (Tosato et al., 2009). We have now evidence that an analogous alteration to genomic homeostasis happens at the proteomic level, with the de-regulation of the level of many proteins involved in almost all the cellular functions. In this area, the first complete proteomic analysis, based on the 2D gel electrophoretic technique coupled with MALDI-TOF mass-spectrometry analysis, provided us with a general view of the differential protein profile between parental and translocant strains. This study revealed the altered expression of at least 24 proteins involved in energy metabolism, stress response, cell cycle, amino acids and cell wall biosynthesis in the translocant strains (Nikitin et al. 2009). We are currently defining the genes architect of the BIT system, concentrating on those that have influence in the various aspects of DNA recombination and repair  using a variety of methods, including the FUN staining, indicating the functionality of cytological physiology (Fig. 1). This should bring more insights into genetic adaptation following gross chromosomal rearrangements and serve as model to further understand the cellular and molecular effects of chromosome translocation and its aetiology of neoplastic transformation in mammals.
As a recent spin-off of these studies, we have undertaken a new research project to apply our BIT chromosomal know-how to the deletion of an extranumerary human chromosome 21 from mouse cells.

Recent Publications

Tosato, V., Nicolini, C., Bruschi, C.V. 2009. DNA bridging of homologous chromosomes in yeast leads to near-reciprocal translocation and loss of heterozygosity by deletion. Chromosoma 118, 179-191

Nikitin, D., Tosato, V., Zavec, A.B., Bruschi, C.V. 2008. Cellular and molecular effects of non-reciprocal chromosome translocations in S. cerevisiae. PNAS 105, 9703-9708

Laun, P., Bruschi, C.V., Dickinson, R., Rinnerthaler, M., Heeren, G., Schwimbersky, R., Rid, R., Breitenbach, M. 2007. Yeast mother cell-specific aging, genetic (in)stability, and the somatic mutation theory of aging. Nucl. Acids Res. 35, 7514-7526

Bruschi, C.V., Gjuracic, K., Tosato, V. 2006. Yeast artificial chromosomes. In: Encyclopedia of Life Sciences, J. Wiley & Sons Ltd., Chichester

Tosato, V., Waghmare, S.K., Bruschi, C.V. 2005. Non-reciprocal chromosomal bridge-induced translocation (BIT) by targeted DNA integration in yeast. Chromosoma, 114, 15-27