# FEN1-mediated Okazaki fragment maturation and its deficiency in cancer

> **NIH NIH R01** · BECKMAN RESEARCH INSTITUTE/CITY OF HOPE · 2020 · $369,788

## Abstract

Abstract
The long-term goal of this project is to determine how defects in flap endonuclease 1 (FEN1)-mediated
Okazaki fragment maturation (OFM) cause genomic instability and contribute to human cancer initiation,
progression, and drug resistance. In the lagging strand DNA synthesis process, proofreading deficient primase
and polymerase α (Pol α) synthesize the RNA primers and the DNA fragment connected to the primers (α-
segment). OFM is a fundamental mechanism for faithful DNA replication, which can be divided into two steps:
RNA primer removal (RPR) and α-segment error editing (AEE). Recent data indicate that the α-segment
accounts for approximately 1.5% of the genome. Therefore, defective OFM can be a significant source of DNA
mutations. Our recent published work indicates that AEE depends on FEN1’s exonuclease (EXO) activity,
whereas RPR requires its structure-specific endonuclease (FEN) activity. In addition, sequential post-
translational modifications (PTMs), which mediate FEN1’s interactions with other DNA replication machinery
components, such as PCNA, WRN, and MutS, are crucial for highly organized OFM. However, many
questions remain unanswered. How is the FEN1-mediated OFM process sequentially coordinated among the
major enzyme actions and with downstream histone deposition? How is the function of OFM complexes
influenced by cellular stresses, such as chemo- and radio- therapeutic stresses? Consequently, how does the
dysfunctional OFM complex promote therapeutic resistance? Based on our exciting preliminary data, we
hypothesize that programmed PTMs of FEN1, dynamic interaction between the OFM machinery and histone
deposition, and HSP70-mediated OFM complex coordination are key regulatory mechanisms for efficient and
accurate FEN1-mediated OFM. Alterations in these regulatory mechanisms may impair OFM and dramatically
increase the mutation frequency, cancer predisposition, and development of drug resistance. We will test the
hypothesis with the following specific aims: 1) To determine the role of arginine demethylase (JMJD1B)-
mediated FEN1 demethylation in OFM. 2) To determine if the dynamic balance between FEN1-mediated OFM
and histone deposition, assembly, and positioning ensures accurate replication of genetic and epigenetic
information. 3) To determine if HSP70 is critical for the correct assembly of functional OFM complexes to
suppress DNA mutations and chemotherapeutic resistance. The current renewal application is based on
successful completion of all the proposed work for the last cycle of funding with 13 peer-reviewed publications,
including publications in high-impact journals, establishment of state-of-the-art experimental systems and
exciting preliminary data that support the paradigm-shifting hypotheses. We are in a unique position to address
these questions because of our initial observations and the experimental systems established in my laboratory.

## Key facts

- **NIH application ID:** 10016177
- **Project number:** 5R01CA073764-24
- **Recipient organization:** BECKMAN RESEARCH INSTITUTE/CITY OF HOPE
- **Principal Investigator:** BINGHUI SHEN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $369,788
- **Award type:** 5
- **Project period:** 1997-05-01 → 2022-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10016177

## Citation

> US National Institutes of Health, RePORTER application 10016177, FEN1-mediated Okazaki fragment maturation and its deficiency in cancer (5R01CA073764-24). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10016177. Licensed CC0.

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