# Project 1: Mitotic Gene Bookmarking as an Epigenetic Mechanism to Maintain the Mammary Epithelial Phenotype

> **NIH NIH P01** · UNIVERSITY OF VERMONT & ST AGRIC COLLEGE · 2021 · $413,163

## Abstract

PROJECT 1 | SUMMARY
Mechanisms underlying the epithelial to mesenchymal transition (EMT)—a normal developmental process and
an early event at the onset of epithelium-derived cancers—are minimally understood. Our findings, corroborated
by others in multiple biologically relevant models, have established mitotic gene bookmarking—occupancy of
target genes by transcription factors during mitosis—as a novel dimension to epigenetic control of lineage
commitment and cell identity. Because EMT results from loss of the epithelial phenotype, Project 1 will address
whether disruption of mitotic gene bookmarking constitutes a key mechanistic component of EMT.
Recently, we have shown that depletion of the RUNX1 transcription factor in normal mammary epithelial (NME)
cells results in EMT in both in vivo and cell-based models, indicating that RUNX1 stabilizes the normal ME
phenotype. Our preliminary data show that in ME cells undergoing mitosis, RUNX1 bookmarks genes involved
in cell proliferation, growth and maintenance of the epithelial phenotype. These findings provide the rationale for
our hypothesis that mitotic bookmarking of target genes by RUNX1 is a key epigenetic mechanism for
maintenance of the normal mammary epithelial phenotype, and perturbation of this mechanism leads to EMT.
Innovative molecular and cellular experimental strategies will be combined with state-of-the-art genomics
approaches to investigate how the RUNX1 mitotic epigenome contributes to initiation of EMT, an early event that
leads to development of breast cancer. Aim 1 will use candidate and unbiased CRISPR screens to determine
how RUNX1 bookmarked genes are physiologically linked to the mammary epithelial phenotype and whether
estrogen receptor signaling—a key determinant of NME phenotype—plays a role in regulation of RUNX1-
bookmarked genes. Aim 2 will employ Hi-ChIP and HIPMap to establish whether RUNX1 bookmarked genes
reside in same genomic neighborhoods for coordinate control. We will assess whether disruption of these
genomic regions confers EMT. Aim 3 will take advantage of degron-based RUNX1 depletion to investigate the
regulatory impact of RUNX1 mitotic bookmarking on target gene expression and maintenance of the NME
phenotype.
Project 1 studies will address significant gaps in current knowledge of the epigenetic mechanisms that regulate
EMT. Our findings will establish RUNX1 mitotic bookmarking as a unique dimension to epigenetic control of the
normal mammary epithelial phenotype, which when disrupted, results in EMT, a key early event in the
development and progression of breast cancer.

## Key facts

- **NIH application ID:** 10107341
- **Project number:** 1P01CA240685-01A1
- **Recipient organization:** UNIVERSITY OF VERMONT & ST AGRIC COLLEGE
- **Principal Investigator:** Gary S. Stein
- **Activity code:** P01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $413,163
- **Award type:** 1
- **Project period:** 2021-04-01 → 2026-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10107341

## Citation

> US National Institutes of Health, RePORTER application 10107341, Project 1: Mitotic Gene Bookmarking as an Epigenetic Mechanism to Maintain the Mammary Epithelial Phenotype (1P01CA240685-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10107341. Licensed CC0.

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