# Mechanism of APE1 in DNA damage response

> **NIH NIH R01** · UNIVERSITY OF NORTH CAROLINA CHARLOTTE · 2020 · $360,794

## Abstract

Project Summary/Abstract
DNA single-strand breaks (SSBs) can be caused by oxidative stress, or intermediate products of various
DNA metabolisms including DNA replication and damage repair. Unrepaired oxidative DNA damage and
SSBs may result in replication fork collapse or transcription machinery failure. Oxidative DNA damage
and SSBs are critical challenges to genomic stability and can lead to tumorigenesis when they are not
repaired quickly or properly. Current understanding of molecular mechanisms underlying checkpoint
signaling and regulatory mechanisms in response to oxidative DNA damage and SSBs is limited or
indirect because of the lack of feasible experimental systems. Whereas APE1 (AP endonuclease 1) is
known for its critical functions in base excision repair and transcriptional regulation, it is currently
unknown whether APE1 plays an essential role in DNA damage response (DDR) pathway. Our published
work and substantial preliminary data suggest that APE1 is essential for activating the ATR-dependent
DDR pathway in oxidative stress, that a distinct ATR-Chk1 checkpoint response is activated by a defined
plasmid-based SSB structure, and that APE1 associates with ATRIP and TopBP1. Our major hypothesis
is that APE1 plays an vital role in checkpoint signaling in response to oxidative stress and SSBs. To test
this directly, our specific aims include: (1) to determine whether APE1 plays an important role in the
initiation of SSB end resection in the 3'-5 direction via its exonuclease activity for the SSB signaling; (2)
to determine how APE1 interacts with ATRIP in DDR pathway, and (3) to determine how TopBP1 is
regulated to activate the ATR-Chk1 checkpoint signaling and whether the role of APE1 in DDR is
conserved in pancreatic cancer cells. We have established two complementary approaches to study
checkpoint signaling pathway: (1) hydrogen peroxide-induced multiple SSBs randomly distributed on
chromatin in a replicating Xenopus LSS system, and (2) plasmid-based site-specific SSB structures in a
nonreplicating Xenopus HSS system. Using innovative biochemical and structure-function analysis in
Xenopus egg extracts, we will demonstrate how oxidative DNA damage and SSBs are recognized and
processed by APE1 in coordination with ATRIP and TopBP1 to regulate checkpoint signaling. We will
also validate our findings from Xenopus egg extract system in mammalian cells including pancreatic
cancer cells. The anticipated outcomes of this research project will help us better understand how
genome stability is maintained in cellular response to oxidative DNA damage and SSBs. All together, this
research project will advance our scientific knowledge conceptually on how cancers develop, and open
avenues to new therapeutic strategies, especially for pancreatic cancer.

## Key facts

- **NIH application ID:** 9849259
- **Project number:** 5R01CA225637-03
- **Recipient organization:** UNIVERSITY OF NORTH CAROLINA CHARLOTTE
- **Principal Investigator:** Shan Yan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $360,794
- **Award type:** 5
- **Project period:** 2018-02-13 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9849259

## Citation

> US National Institutes of Health, RePORTER application 9849259, Mechanism of APE1 in DNA damage response (5R01CA225637-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9849259. Licensed CC0.

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