1. 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

2. 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

3. 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…

4. 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.

5. 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

6. Luria Delbruck Fluctuation Test

7. 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.

8. References
Lengronne A., Schwob E., 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., Cell Cycle Regulation of DNA Replication in S. cerevisiae, DNA Replication-Current Advances. InTech, DOI: /19055.
Singh, A., & Xu, Y.-J. (2016). The Cell Killing Mechanisms of Hydroxyurea. Genes, 7(11), 99. DOI: /
Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; An Overview of the Cell Cycle. Available from: