Poster abstracts
Poster number 138 submitted by Mara Stout
The role of topoisomerases in circularized chromosome strains of Saccharomyces cerevisiae
Mara J. Stout (Department of Chemistry and Biology, Morehead State University), Melissa A. Mefford (Department of Chemistry and Biology, Morehead State University)
Abstract:
The genome of eukaryotic cells is characterized by multiple linear chromosomes rather than a single circular chromosome that prokaryotes typically have. Maintenance of telomeres at the end of linear chromosomes requires the ribonucleoprotein complex telomerase. Our lab is particularly interested in understanding why eukaryotic cells evolved telomeres and telomerase. To investigate the role of linear chromosomes in eukaryotes, we have successfully engineered budding yeast, Saccharomyces cerevisiae, with individually circularized chromosomes. In haploid strains undergoing mitotic division, the circularized chromosome strains have no obvious phenotypes compared to wildtype. However, the chromosomes must be segregated differently than wildtype strains due to the large structural difference. We propose segregation of circular chromosomes will require topoisomerases, which are important nuclear enzymes that engage in DNA replication, transcription, chromosome segregation, and recombination. To test this hypothesis, we deleted the non-essential topoisomerase I (TOP1) and III (TOP3) genes in wild-type and circularized chromosome strains of S. cerevisiae. Our preliminary data show that the deletions have no growth defect in wild-type strains, but have a clear growth defect in the circular chromosome strains. To further test our hypothesis, we are growing yeast in the presence of a topoisomerase inhibitor, doxorubicin, which should mimic the effects of topoisomerase gene deletion. Together, our data will shed light on how chromosomal architecture influences chromosomal segregation and cell proliferation. In the future, we also plan to study meiotic division, hopefully elucidating that linear chromosomes are better able to undergo the vital crossing-over process in meiosis and sexual reproduction.
Keywords: telomere, telomerase, topoisomerase