Addressing the role G1 phase length on genetic instability in S Addressing the role G1 phase length on genetic instability in S. cerevisiae Yi H Chen Murray Lab FAS Center for Systems Biology, Department of Molecular and Cellular Biology, Harvard University

The Cell Cycle G1 S G2 M Cell Growth Prepare for DNA replication Prepare for division DNA replication Growth stops Orderly division of two daughter cells START Figure adopted from Alberts B et al., Molecular Biology of the Cell. 2002.

The Cell Cycle: G1 phase G1 S G2 M START G1 Cell Cycle regulators are often mutated in cancer cells, which are characteristically genetically unstable How G1 is related to to genetic instability is unclear…

Hypothesis: G1 phase is the site of preparation for DNA replication Hypothesis: G1 phase is the site of preparation for DNA replication. Does the length of the G1 phase of the cell cycle play a role in genetic instability? Goal: Shorten the length of the G1 phase of the cell cycle by constructing mutants with altered G1 cell cycle regulators.

DNA Damaging Agent YPD YPD + HU WT YP+ Glucose YP + Glucose HU Mutant 1: Known genetically unstable; shortened G1 Mutant 2: Slightly shorter G1 YPD YPD + HU YP+ Glucose YP + Glucose HU YP + Galactose YP + Galactose HU Mutant 4: Shortened G1 Mutant 3: Longer G1

Luria Delbruck Fluctuation Test

Conclusions and Future work Preliminary results suggest that genetic instability is not linearly dependent on length of the G1 phase However, mutant 1 (known to be genetically unstable) was found to have the shortest G1 phase Perhaps G1 phase was not sufficiently reduced in the mutants constructed Further experiments are needed to rule out this possibility. Double mutants and mutants with other altered G1 phase regulators will be constructed.

References Lengronne A., Schwob E., 2002. The yeast CDK inhibitor Sic1 prevents genomic instability by promoting replication origin licensing in late G(1). Mol. Cell DOI: 9: 1067/1078.  Enserink JM., 2011. Cell Cycle Regulation of DNA Replication in S. cerevisiae, DNA Replication-Current Advances. InTech, DOI: 10.5772/19055. Singh, A., & Xu, Y.-J. (2016). The Cell Killing Mechanisms of Hydroxyurea. Genes, 7(11), 99. DOI: 10.3390/7110099 Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002. An Overview of the Cell Cycle. Available from: https://www.ncbi.nlm.nih.gov/books/NBK26869/