UNDERSTANDING THE MECHANISM OF GENOMIC INSTABILITY DURING REPLICATIVE AGING IN BUDDING YEAST

Aging brings a gradual decline in molecular fidelity and biological functionality, resulting in age related phenotypes and diseases. Despite continued efforts to uncover the conserved aging pathways among eukaryotes, exact molecular causes of aging are still poorly understood. One of the most important telomere(definition) attrition, cellular senescence(definition))." style="text-decoration:underline dotted; text-underline-offset:2px; cursor:help;">hallmarks of aging(definition) is increased genomic instability. However, there remains much ambiguity as to the cause. I am studying the replicative life span (RLS) of the genetically tractable model organism Saccharomyces cerevisiae, or budding yeast using the innovative “mother enrichment program” as the method to isolate unparalleled numbers of aged yeast cells to investigate the molecular changes associated with aging. My goal is to determine the possible causes of loss of genomic integrity during replicative aging in budding yeast to gain potential insight into this vastly complex process. In my work presented here, I uncovered a global loss of cohesion in mitotically aged yeast cells and this most likely serves as the cause of increased rDNA instability and/or ERC accumulation as observed during aging. These events, in turn, influence the global genomic integrity in replicatively aged cells. Furthermore, I discovered a profound defect in double strand break (DSB) repair with aging due to limiting levels of key components of the homologous recombination machinery. This DSB repair defect in old cells limited the replicative lifespan, because restoration of DSB repair by overexpressing key HR proteins ameliorated age-associated changes, to extend lifespan. We propose that the limiting levels of repair factors and cohesin proteins impair the ability of the aged cells to counteract the increased burden of genomic damage accumulation coupled with chromosomal rearrangements and potentially chromosome loss, eventually to cross a threshold of genomic damage that is sensed by the cell to cause cessation of cell division marking the end of the replicative lifespan.