Chromosome bridging in yeast models myeloid leukemic translocation in mammalian cells

23rd January 2015
Versione stampabile

Venue: Edificio Povo 2, via Sommarive nr. 9, Povo (TN) - Room B101
 at 2:00 p.m.

  • Valentina TosatoResearch Scientist at the Yeast Molecular Genetics Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste,

In the past, our group developed a system named BIT (Bridge-Induced Translocation) to link together two different yeast chromosomes exploiting the endogenous homologous recombination of Saccharomyces cerevisiae [1]. The BIT translocations are POL32-independent and RAD54-dependent [2] and generate an increase of gene expression around the breakpoint (local effect) and random gene expression alteration in the genome (general effect) [3]. We demonstrated that the same translocation event between two specific chromosomal loci can lead to a heterogeneous population of translocated cells, different among them by the genotypic and phenotypic point of view [4,5,6]. In mammalian cells, liquid tumors are often associated with chromosomal translocations and occasionally with gene fusions. We therefore decided to perform a targeted BIT in Saccharomyces cerevisiae triggering the fusion of the gene NUP145 (orthologue to hNUP98) and TOP2 (orthologue to to hTOP2B) since translocation between these two genes is responsible for acute myeloid leukemia (AML) in humans [7]. In his way, we could model the molecular triggering of AML in yeast.  Thanks to a complex pop-out methodology of the marker used to select for BIT translocant, we succeed in reproducing exactly the same gene fusion found in mammalian cells. The phenotype of the new yeast was weird and was analyzed in details by optical and electron microscopy. The resulting "leukemic" yeast strain can be used as a model to test the role in translocations of oncogenic factors such as P53 and to find new molecular players in translocation events.