CHED 864 |
| The precise replication of DNA in cells is a necessary part of maintaining genomic stability. Spontaneous and induced DNA damage occurring within cells can result in replication fork stalling. Eukaryotic cells have developed pathways to bypass unrepaired/unrepairable damage to avoid permanent fork stalling or collapse which can lead to genomic instability and cancer, or cell death. Stalled replication forks are sensed and trigger cell cycle checkpoint responses which in turn signal for DNA damage repair. The drug adozelesin causes alkylation of DNA, leading to a cell cycle checkpoint activation initiated by Mec1 protein kinase and the RAD5 DNA damage bypass pathway is involved in replication past adozelesin lesions. This information provided the background for our investigation of the genetic interaction between MEC1, controlling the checkpoint response and RAD5 coordinating the lesion bypass. It was found that, whereas the inactivation of either RAD5 or MEC1 conferred high sensitivity to cells exposed to adozelesin in S-phase, with a stronger effect for the RAD5 deletion, the inactivation of both genes in a rad5Δ mec1Δ mutant did not result in an additive phenotype, but induced a suppression of the rad5Δ sensitivity to a level similar to mec1Δ alone. Furthermore, while rad5Δ cells were S-phase checkpoint competent, but failed to undergo mitosis following drug exposure, both mec1Δand rad5Δ mec1Δ cells were deficient in slowing down S-phase progression in response to DNA damage, but were able to complete cell division. Finally, unlike wild-type cells, cells lacking RAD5 were unable to complete chromosomal DNA replication after adozelesin treatment. However, the additional inactivation of MEC1 partly relieved the rad5Δ replication defect, consistent also with the sensitivity suppression. Our findings suggest that the MEC1 gene functions together with the RAD5 gene to help the replication fork bypass DNA damage in S-phase. |
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Undergraduate Research Poster Session: Biochemistry
2:00 PM-4:00 PM, Monday, April 7, 2008 Morial Convention Center -- Hall A, Poster
Division of Chemical Education |