Grants and Contracts Details
Description
The long-term goal of this project is to study how post-translational modifications of DNA mismatch
repair (MMR) proteins impact genome integrity and cancer development. MMR maintains genome
stability by removing mismatches in the newly synthesized strand during DNA replication. The MMR
reaction involves mismatch recognition by the initiation factors (MutSá, MutLá, and PCNA), mismatch
removal by nucleases, and DNA gap-filling by DNA polymerases. The importance of MMR is underscored
by the fact that MMR defects lead to hypermutations and susceptibility to both hereditary and
sporadic colorectal cancers (CRCs). Exhibiting elevated instability in simple repeats, called microsatellite
instability (MSI), is a hallmark of MMR-deficient CRCs. However, only ~70% of hereditary and
sporadic CRC cases that display MSI have identifiable mutations in MMR genes, suggesting that other
mechanism(s) are responsible for the MSI phenotype in the remaining 30% of the cases. We recently
showed that CRC cells containing high levels of PCNA tyrosine phosphorylation are defective
in MMR in vitro. We therefore hypothesize that PCNA phosphorylation inhibits MMR, leading to genome
instability and CRC development. To test this hypothesis, three Specific Aims are proposed.
Aim 1 is to determine how phosphorylated PCNA inhibits MMR. A well-defined in vitro MMR reaction
will be conducted in both a nuclear extract system and a reconstituted system in the presence or absence
of phosphorylated PCNA, and analysis of the repair products will allow determination of the
specific step(s) of the reaction that is blocked. Aim 2 is to determine hypermutability and MMR proficiency
in cells stably expressing phosphorylated PCNA mimics while suppressed for endogenous
PCNA expression. Aim 3 is to analyze tumorigenesis in transgenic mice expressing phosphorylated
PCNA. A successful completion of the proposed work will establish PCNA tyrosine phosphorylation as
a novel biomarker for cancer etiology and progression.
Status | Finished |
---|---|
Effective start/end date | 2/15/13 → 7/31/15 |
Funding
- National Cancer Institute: $483,311.00
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