Systematic identification and characterization of genes that suppress gross chromosomal rearrangements.
Pamela Kanellis, Aimee Galacia, Melanie Partington, Daniel Durocher
Molecular and Medical Genetics, Samuel Lunenfeld/U of Toronto, 600 University Ave, Toronto, ON, M5G1X5, Canada
Genetic instability is a hallmark of cancer and the accumulation of mutations within a cell may promote its development and/or progression. To identify novel regulators of genome instability, I have developed approaches to systematically screen for genes that suppress the formation of gross chromosomal rearrangements (GCR). This specific type of genetic instability encompasses non-reciprocal translocations, interstitial and chromosome arm deletions. Using the budding yeast as a model to measure chromosomal aberrations, I have inserted counter-selectable genes CAN1 and URA3 10Kb from the telomere on Chr XV. To repair double-strand breaks (DSB) in this region, this strain predominantly uses break-induced replication using two highly conserved regions that share 85-97% identity with other chromosomes. To implement the screen, we systematically produced ~5000 haploid deletion mutants with the CAN1 - URA3 modification and subjected them to a papillation test and a barcode microarray approach. These approaches have identified several known GCR suppressors including MRE11, XRS2, RAD50, RAD5, SGS1, TOP3 and RAD27 along with a group of 10 novel genes including SLX8, HEX3, ESC2 and WSS1.Currently, I am investigating these potentially novel GCR suppression pathways and understanding their role in replication fork integrity and DSB repair. In the long-term, identification of GCR suppressors in yeast may help us to identify human orthologs which function as caretakers in human cancers.